From 2e86230fcb918172751b4aadeb5782409e769988 Mon Sep 17 00:00:00 2001 From: Axel Lin Date: Thu, 31 Oct 2013 11:23:46 +0800 Subject: [PATCH 01/12] gpio: tb10x: Set output value before setting direction to output Signed-off-by: Axel Lin Acked-by: Christian Ruppert Signed-off-by: Linus Walleij --- drivers/gpio/gpio-tb10x.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/gpio/gpio-tb10x.c b/drivers/gpio/gpio-tb10x.c index 0502b9a041a5..da071ddbad99 100644 --- a/drivers/gpio/gpio-tb10x.c +++ b/drivers/gpio/gpio-tb10x.c @@ -132,6 +132,7 @@ static int tb10x_gpio_direction_out(struct gpio_chip *chip, int mask = BIT(offset); int val = TB10X_GPIO_DIR_OUT << offset; + tb10x_gpio_set(chip, offset, value); tb10x_set_bits(tb10x_gpio, OFFSET_TO_REG_DDR, mask, val); return 0; From fd8e198cfcaa8abcc7f7525619d447f9a805e86e Mon Sep 17 00:00:00 2001 From: Alexandre Courbot Date: Sat, 16 Nov 2013 21:34:21 +0900 Subject: [PATCH 02/12] Documentation: gpiolib: document new interface gpiolib now exports a new descriptor-based interface which deprecates the older integer-based one. This patch documents this new interface and also takes the opportunity to brush-up the GPIO documentation a little bit. The new descriptor-based interface follows the same consumer/driver model as many other kernel subsystems (e.g. clock, regulator), so its documentation has similarly been splitted into different files. The content of the former documentation has been reused whenever it made sense; however, some of its content did not apply to the new interface anymore and have this been removed. Likewise, new sections like the mapping of GPIOs to devices have been written from scratch. The deprecated legacy-based documentation is still available, untouched, under Documentation/gpio/gpio-legacy.txt. Signed-off-by: Alexandre Courbot Signed-off-by: Linus Walleij --- Documentation/gpio/board.txt | 115 ++++++++++ Documentation/gpio/consumer.txt | 197 ++++++++++++++++++ Documentation/gpio/driver.txt | 75 +++++++ .../{gpio.txt => gpio/gpio-legacy.txt} | 0 Documentation/gpio/gpio.txt | 119 +++++++++++ Documentation/gpio/sysfs.txt | 155 ++++++++++++++ 6 files changed, 661 insertions(+) create mode 100644 Documentation/gpio/board.txt create mode 100644 Documentation/gpio/consumer.txt create mode 100644 Documentation/gpio/driver.txt rename Documentation/{gpio.txt => gpio/gpio-legacy.txt} (100%) create mode 100644 Documentation/gpio/gpio.txt create mode 100644 Documentation/gpio/sysfs.txt diff --git a/Documentation/gpio/board.txt b/Documentation/gpio/board.txt new file mode 100644 index 000000000000..0d03506f2cc5 --- /dev/null +++ b/Documentation/gpio/board.txt @@ -0,0 +1,115 @@ +GPIO Mappings +============= + +This document explains how GPIOs can be assigned to given devices and functions. +Note that it only applies to the new descriptor-based interface. For a +description of the deprecated integer-based GPIO interface please refer to +gpio-legacy.txt (actually, there is no real mapping possible with the old +interface; you just fetch an integer from somewhere and request the +corresponding GPIO. + +Platforms that make use of GPIOs must select ARCH_REQUIRE_GPIOLIB (if GPIO usage +is mandatory) or ARCH_WANT_OPTIONAL_GPIOLIB (if GPIO support can be omitted) in +their Kconfig. Then, how GPIOs are mapped depends on what the platform uses to +describe its hardware layout. Currently, mappings can be defined through device +tree, ACPI, and platform data. + +Device Tree +----------- +GPIOs can easily be mapped to devices and functions in the device tree. The +exact way to do it depends on the GPIO controller providing the GPIOs, see the +device tree bindings for your controller. + +GPIOs mappings are defined in the consumer device's node, in a property named +-gpios, where is the function the driver will request +through gpiod_get(). For example: + + foo_device { + compatible = "acme,foo"; + ... + led-gpios = <&gpio 15 GPIO_ACTIVE_HIGH>, /* red */ + <&gpio 16 GPIO_ACTIVE_HIGH>, /* green */ + <&gpio 17 GPIO_ACTIVE_HIGH>; /* blue */ + + power-gpio = <&gpio 1 GPIO_ACTIVE_LOW>; + }; + +This property will make GPIOs 15, 16 and 17 available to the driver under the +"led" function, and GPIO 1 as the "power" GPIO: + + struct gpio_desc *red, *green, *blue, *power; + + red = gpiod_get_index(dev, "led", 0); + green = gpiod_get_index(dev, "led", 1); + blue = gpiod_get_index(dev, "led", 2); + + power = gpiod_get(dev, "power"); + +The led GPIOs will be active-high, while the power GPIO will be active-low (i.e. +gpiod_is_active_low(power) will be true). + +ACPI +---- +ACPI does not support function names for GPIOs. Therefore, only the "idx" +argument of gpiod_get_index() is useful to discriminate between GPIOs assigned +to a device. The "con_id" argument can still be set for debugging purposes (it +will appear under error messages as well as debug and sysfs nodes). + +Platform Data +------------- +Finally, GPIOs can be bound to devices and functions using platform data. Board +files that desire to do so need to include the following header: + + #include + +GPIOs are mapped by the means of tables of lookups, containing instances of the +gpiod_lookup structure. Two macros are defined to help declaring such mappings: + + GPIO_LOOKUP(chip_label, chip_hwnum, dev_id, con_id, flags) + GPIO_LOOKUP_IDX(chip_label, chip_hwnum, dev_id, con_id, idx, flags) + +where + + - chip_label is the label of the gpiod_chip instance providing the GPIO + - chip_hwnum is the hardware number of the GPIO within the chip + - dev_id is the identifier of the device that will make use of this GPIO. If + NULL, the GPIO will be available to all devices. + - con_id is the name of the GPIO function from the device point of view. It + can be NULL. + - idx is the index of the GPIO within the function. + - flags is defined to specify the following properties: + * GPIOF_ACTIVE_LOW - to configure the GPIO as active-low + * GPIOF_OPEN_DRAIN - GPIO pin is open drain type. + * GPIOF_OPEN_SOURCE - GPIO pin is open source type. + +In the future, these flags might be extended to support more properties. + +Note that GPIO_LOOKUP() is just a shortcut to GPIO_LOOKUP_IDX() where idx = 0. + +A lookup table can then be defined as follows: + + struct gpiod_lookup gpios_table[] = { + GPIO_LOOKUP_IDX("gpio.0", 15, "foo.0", "led", 0, GPIO_ACTIVE_HIGH), + GPIO_LOOKUP_IDX("gpio.0", 16, "foo.0", "led", 1, GPIO_ACTIVE_HIGH), + GPIO_LOOKUP_IDX("gpio.0", 17, "foo.0", "led", 2, GPIO_ACTIVE_HIGH), + GPIO_LOOKUP("gpio.0", 1, "foo.0", "power", GPIO_ACTIVE_LOW), + }; + +And the table can be added by the board code as follows: + + gpiod_add_table(gpios_table, ARRAY_SIZE(gpios_table)); + +The driver controlling "foo.0" will then be able to obtain its GPIOs as follows: + + struct gpio_desc *red, *green, *blue, *power; + + red = gpiod_get_index(dev, "led", 0); + green = gpiod_get_index(dev, "led", 1); + blue = gpiod_get_index(dev, "led", 2); + + power = gpiod_get(dev, "power"); + gpiod_direction_output(power, 1); + +Since the "power" GPIO is mapped as active-low, its actual signal will be 0 +after this code. Contrary to the legacy integer GPIO interface, the active-low +property is handled during mapping and is thus transparent to GPIO consumers. diff --git a/Documentation/gpio/consumer.txt b/Documentation/gpio/consumer.txt new file mode 100644 index 000000000000..07c74a3765a0 --- /dev/null +++ b/Documentation/gpio/consumer.txt @@ -0,0 +1,197 @@ +GPIO Descriptor Consumer Interface +================================== + +This document describes the consumer interface of the GPIO framework. Note that +it describes the new descriptor-based interface. For a description of the +deprecated integer-based GPIO interface please refer to gpio-legacy.txt. + + +Guidelines for GPIOs consumers +============================== + +Drivers that can't work without standard GPIO calls should have Kconfig entries +that depend on GPIOLIB. The functions that allow a driver to obtain and use +GPIOs are available by including the following file: + + #include + +All the functions that work with the descriptor-based GPIO interface are +prefixed with gpiod_. The gpio_ prefix is used for the legacy interface. No +other function in the kernel should use these prefixes. + + +Obtaining and Disposing GPIOs +============================= + +With the descriptor-based interface, GPIOs are identified with an opaque, +non-forgeable handler that must be obtained through a call to one of the +gpiod_get() functions. Like many other kernel subsystems, gpiod_get() takes the +device that will use the GPIO and the function the requested GPIO is supposed to +fulfill: + + struct gpio_desc *gpiod_get(struct device *dev, const char *con_id) + +If a function is implemented by using several GPIOs together (e.g. a simple LED +device that displays digits), an additional index argument can be specified: + + struct gpio_desc *gpiod_get_index(struct device *dev, + const char *con_id, unsigned int idx) + +Both functions return either a valid GPIO descriptor, or an error code checkable +with IS_ERR(). They will never return a NULL pointer. + +Device-managed variants of these functions are also defined: + + struct gpio_desc *devm_gpiod_get(struct device *dev, const char *con_id) + + struct gpio_desc *devm_gpiod_get_index(struct device *dev, + const char *con_id, + unsigned int idx) + +A GPIO descriptor can be disposed of using the gpiod_put() function: + + void gpiod_put(struct gpio_desc *desc) + +It is strictly forbidden to use a descriptor after calling this function. The +device-managed variant is, unsurprisingly: + + void devm_gpiod_put(struct device *dev, struct gpio_desc *desc) + + +Using GPIOs +=========== + +Setting Direction +----------------- +The first thing a driver must do with a GPIO is setting its direction. This is +done by invoking one of the gpiod_direction_*() functions: + + int gpiod_direction_input(struct gpio_desc *desc) + int gpiod_direction_output(struct gpio_desc *desc, int value) + +The return value is zero for success, else a negative errno. It should be +checked, since the get/set calls don't return errors and since misconfiguration +is possible. You should normally issue these calls from a task context. However, +for spinlock-safe GPIOs it is OK to use them before tasking is enabled, as part +of early board setup. + +For output GPIOs, the value provided becomes the initial output value. This +helps avoid signal glitching during system startup. + +A driver can also query the current direction of a GPIO: + + int gpiod_get_direction(const struct gpio_desc *desc) + +This function will return either GPIOF_DIR_IN or GPIOF_DIR_OUT. + +Be aware that there is no default direction for GPIOs. Therefore, **using a GPIO +without setting its direction first is illegal and will result in undefined +behavior!** + + +Spinlock-Safe GPIO Access +------------------------- +Most GPIO controllers can be accessed with memory read/write instructions. Those +don't need to sleep, and can safely be done from inside hard (non-threaded) IRQ +handlers and similar contexts. + +Use the following calls to access GPIOs from an atomic context: + + int gpiod_get_value(const struct gpio_desc *desc); + void gpiod_set_value(struct gpio_desc *desc, int value); + +The values are boolean, zero for low, nonzero for high. When reading the value +of an output pin, the value returned should be what's seen on the pin. That +won't always match the specified output value, because of issues including +open-drain signaling and output latencies. + +The get/set calls do not return errors because "invalid GPIO" should have been +reported earlier from gpiod_direction_*(). However, note that not all platforms +can read the value of output pins; those that can't should always return zero. +Also, using these calls for GPIOs that can't safely be accessed without sleeping +(see below) is an error. + + +GPIO Access That May Sleep +-------------------------- +Some GPIO controllers must be accessed using message based buses like I2C or +SPI. Commands to read or write those GPIO values require waiting to get to the +head of a queue to transmit a command and get its response. This requires +sleeping, which can't be done from inside IRQ handlers. + +Platforms that support this type of GPIO distinguish them from other GPIOs by +returning nonzero from this call: + + int gpiod_cansleep(const struct gpio_desc *desc) + +To access such GPIOs, a different set of accessors is defined: + + int gpiod_get_value_cansleep(const struct gpio_desc *desc) + void gpiod_set_value_cansleep(struct gpio_desc *desc, int value) + +Accessing such GPIOs requires a context which may sleep, for example a threaded +IRQ handler, and those accessors must be used instead of spinlock-safe +accessors without the cansleep() name suffix. + +Other than the fact that these accessors might sleep, and will work on GPIOs +that can't be accessed from hardIRQ handlers, these calls act the same as the +spinlock-safe calls. + + +Active-low State and Raw GPIO Values +------------------------------------ +Device drivers like to manage the logical state of a GPIO, i.e. the value their +device will actually receive, no matter what lies between it and the GPIO line. +In some cases, it might make sense to control the actual GPIO line value. The +following set of calls ignore the active-low property of a GPIO and work on the +raw line value: + + int gpiod_get_raw_value(const struct gpio_desc *desc) + void gpiod_set_raw_value(struct gpio_desc *desc, int value) + int gpiod_get_raw_value_cansleep(const struct gpio_desc *desc) + void gpiod_set_raw_value_cansleep(struct gpio_desc *desc, int value) + +The active-low state of a GPIO can also be queried using the following call: + + int gpiod_is_active_low(const struct gpio_desc *desc) + +Note that these functions should only be used with great moderation ; a driver +should not have to care about the physical line level. + +GPIOs mapped to IRQs +-------------------- +GPIO lines can quite often be used as IRQs. You can get the IRQ number +corresponding to a given GPIO using the following call: + + int gpiod_to_irq(const struct gpio_desc *desc) + +It will return an IRQ number, or an negative errno code if the mapping can't be +done (most likely because that particular GPIO cannot be used as IRQ). It is an +unchecked error to use a GPIO that wasn't set up as an input using +gpiod_direction_input(), or to use an IRQ number that didn't originally come +from gpiod_to_irq(). gpiod_to_irq() is not allowed to sleep. + +Non-error values returned from gpiod_to_irq() can be passed to request_irq() or +free_irq(). They will often be stored into IRQ resources for platform devices, +by the board-specific initialization code. Note that IRQ trigger options are +part of the IRQ interface, e.g. IRQF_TRIGGER_FALLING, as are system wakeup +capabilities. + + +Interacting With the Legacy GPIO Subsystem +========================================== +Many kernel subsystems still handle GPIOs using the legacy integer-based +interface. Although it is strongly encouraged to upgrade them to the safer +descriptor-based API, the following two functions allow you to convert a GPIO +descriptor into the GPIO integer namespace and vice-versa: + + int desc_to_gpio(const struct gpio_desc *desc) + struct gpio_desc *gpio_to_desc(unsigned gpio) + +The GPIO number returned by desc_to_gpio() can be safely used as long as the +GPIO descriptor has not been freed. All the same, a GPIO number passed to +gpio_to_desc() must have been properly acquired, and usage of the returned GPIO +descriptor is only possible after the GPIO number has been released. + +Freeing a GPIO obtained by one API with the other API is forbidden and an +unchecked error. diff --git a/Documentation/gpio/driver.txt b/Documentation/gpio/driver.txt new file mode 100644 index 000000000000..9da0bfa74781 --- /dev/null +++ b/Documentation/gpio/driver.txt @@ -0,0 +1,75 @@ +GPIO Descriptor Driver Interface +================================ + +This document serves as a guide for GPIO chip drivers writers. Note that it +describes the new descriptor-based interface. For a description of the +deprecated integer-based GPIO interface please refer to gpio-legacy.txt. + +Each GPIO controller driver needs to include the following header, which defines +the structures used to define a GPIO driver: + + #include + + +Internal Representation of GPIOs +================================ + +Inside a GPIO driver, individual GPIOs are identified by their hardware number, +which is a unique number between 0 and n, n being the number of GPIOs managed by +the chip. This number is purely internal: the hardware number of a particular +GPIO descriptor is never made visible outside of the driver. + +On top of this internal number, each GPIO also need to have a global number in +the integer GPIO namespace so that it can be used with the legacy GPIO +interface. Each chip must thus have a "base" number (which can be automatically +assigned), and for each GPIO the global number will be (base + hardware number). +Although the integer representation is considered deprecated, it still has many +users and thus needs to be maintained. + +So for example one platform could use numbers 32-159 for GPIOs, with a +controller defining 128 GPIOs at a "base" of 32 ; while another platform uses +numbers 0..63 with one set of GPIO controllers, 64-79 with another type of GPIO +controller, and on one particular board 80-95 with an FPGA. The numbers need not +be contiguous; either of those platforms could also use numbers 2000-2063 to +identify GPIOs in a bank of I2C GPIO expanders. + + +Controller Drivers: gpio_chip +============================= + +In the gpiolib framework each GPIO controller is packaged as a "struct +gpio_chip" (see linux/gpio/driver.h for its complete definition) with members +common to each controller of that type: + + - methods to establish GPIO direction + - methods used to access GPIO values + - method to return the IRQ number associated to a given GPIO + - flag saying whether calls to its methods may sleep + - optional debugfs dump method (showing extra state like pullup config) + - optional base number (will be automatically assigned if omitted) + - label for diagnostics and GPIOs mapping using platform data + +The code implementing a gpio_chip should support multiple instances of the +controller, possibly using the driver model. That code will configure each +gpio_chip and issue gpiochip_add(). Removing a GPIO controller should be rare; +use gpiochip_remove() when it is unavoidable. + +Most often a gpio_chip is part of an instance-specific structure with state not +exposed by the GPIO interfaces, such as addressing, power management, and more. +Chips such as codecs will have complex non-GPIO state. + +Any debugfs dump method should normally ignore signals which haven't been +requested as GPIOs. They can use gpiochip_is_requested(), which returns either +NULL or the label associated with that GPIO when it was requested. + +Locking IRQ usage +----------------- +Input GPIOs can be used as IRQ signals. When this happens, a driver is requested +to mark the GPIO as being used as an IRQ: + + int gpiod_lock_as_irq(struct gpio_desc *desc) + +This will prevent the use of non-irq related GPIO APIs until the GPIO IRQ lock +is released: + + void gpiod_unlock_as_irq(struct gpio_desc *desc) diff --git a/Documentation/gpio.txt b/Documentation/gpio/gpio-legacy.txt similarity index 100% rename from Documentation/gpio.txt rename to Documentation/gpio/gpio-legacy.txt diff --git a/Documentation/gpio/gpio.txt b/Documentation/gpio/gpio.txt new file mode 100644 index 000000000000..cd9b356e88cd --- /dev/null +++ b/Documentation/gpio/gpio.txt @@ -0,0 +1,119 @@ +GPIO Interfaces +=============== + +The documents in this directory give detailed instructions on how to access +GPIOs in drivers, and how to write a driver for a device that provides GPIOs +itself. + +Due to the history of GPIO interfaces in the kernel, there are two different +ways to obtain and use GPIOs: + + - The descriptor-based interface is the preferred way to manipulate GPIOs, +and is described by all the files in this directory excepted gpio-legacy.txt. + - The legacy integer-based interface which is considered deprecated (but still +usable for compatibility reasons) is documented in gpio-legacy.txt. + +The remainder of this document applies to the new descriptor-based interface. +gpio-legacy.txt contains the same information applied to the legacy +integer-based interface. + + +What is a GPIO? +=============== + +A "General Purpose Input/Output" (GPIO) is a flexible software-controlled +digital signal. They are provided from many kinds of chip, and are familiar +to Linux developers working with embedded and custom hardware. Each GPIO +represents a bit connected to a particular pin, or "ball" on Ball Grid Array +(BGA) packages. Board schematics show which external hardware connects to +which GPIOs. Drivers can be written generically, so that board setup code +passes such pin configuration data to drivers. + +System-on-Chip (SOC) processors heavily rely on GPIOs. In some cases, every +non-dedicated pin can be configured as a GPIO; and most chips have at least +several dozen of them. Programmable logic devices (like FPGAs) can easily +provide GPIOs; multifunction chips like power managers, and audio codecs +often have a few such pins to help with pin scarcity on SOCs; and there are +also "GPIO Expander" chips that connect using the I2C or SPI serial buses. +Most PC southbridges have a few dozen GPIO-capable pins (with only the BIOS +firmware knowing how they're used). + +The exact capabilities of GPIOs vary between systems. Common options: + + - Output values are writable (high=1, low=0). Some chips also have + options about how that value is driven, so that for example only one + value might be driven, supporting "wire-OR" and similar schemes for the + other value (notably, "open drain" signaling). + + - Input values are likewise readable (1, 0). Some chips support readback + of pins configured as "output", which is very useful in such "wire-OR" + cases (to support bidirectional signaling). GPIO controllers may have + input de-glitch/debounce logic, sometimes with software controls. + + - Inputs can often be used as IRQ signals, often edge triggered but + sometimes level triggered. Such IRQs may be configurable as system + wakeup events, to wake the system from a low power state. + + - Usually a GPIO will be configurable as either input or output, as needed + by different product boards; single direction ones exist too. + + - Most GPIOs can be accessed while holding spinlocks, but those accessed + through a serial bus normally can't. Some systems support both types. + +On a given board each GPIO is used for one specific purpose like monitoring +MMC/SD card insertion/removal, detecting card write-protect status, driving +a LED, configuring a transceiver, bit-banging a serial bus, poking a hardware +watchdog, sensing a switch, and so on. + + +Common GPIO Properties +====================== + +These properties are met through all the other documents of the GPIO interface +and it is useful to understand them, especially if you need to define GPIO +mappings. + +Active-High and Active-Low +-------------------------- +It is natural to assume that a GPIO is "active" when its output signal is 1 +("high"), and inactive when it is 0 ("low"). However in practice the signal of a +GPIO may be inverted before is reaches its destination, or a device could decide +to have different conventions about what "active" means. Such decisions should +be transparent to device drivers, therefore it is possible to define a GPIO as +being either active-high ("1" means "active", the default) or active-low ("0" +means "active") so that drivers only need to worry about the logical signal and +not about what happens at the line level. + +Open Drain and Open Source +-------------------------- +Sometimes shared signals need to use "open drain" (where only the low signal +level is actually driven), or "open source" (where only the high signal level is +driven) signaling. That term applies to CMOS transistors; "open collector" is +used for TTL. A pullup or pulldown resistor causes the high or low signal level. +This is sometimes called a "wire-AND"; or more practically, from the negative +logic (low=true) perspective this is a "wire-OR". + +One common example of an open drain signal is a shared active-low IRQ line. +Also, bidirectional data bus signals sometimes use open drain signals. + +Some GPIO controllers directly support open drain and open source outputs; many +don't. When you need open drain signaling but your hardware doesn't directly +support it, there's a common idiom you can use to emulate it with any GPIO pin +that can be used as either an input or an output: + + LOW: gpiod_direction_output(gpio, 0) ... this drives the signal and overrides + the pullup. + + HIGH: gpiod_direction_input(gpio) ... this turns off the output, so the pullup + (or some other device) controls the signal. + +The same logic can be applied to emulate open source signaling, by driving the +high signal and configuring the GPIO as input for low. This open drain/open +source emulation can be handled transparently by the GPIO framework. + +If you are "driving" the signal high but gpiod_get_value(gpio) reports a low +value (after the appropriate rise time passes), you know some other component is +driving the shared signal low. That's not necessarily an error. As one common +example, that's how I2C clocks are stretched: a slave that needs a slower clock +delays the rising edge of SCK, and the I2C master adjusts its signaling rate +accordingly. diff --git a/Documentation/gpio/sysfs.txt b/Documentation/gpio/sysfs.txt new file mode 100644 index 000000000000..c2c3a97f8ff7 --- /dev/null +++ b/Documentation/gpio/sysfs.txt @@ -0,0 +1,155 @@ +GPIO Sysfs Interface for Userspace +================================== + +Platforms which use the "gpiolib" implementors framework may choose to +configure a sysfs user interface to GPIOs. This is different from the +debugfs interface, since it provides control over GPIO direction and +value instead of just showing a gpio state summary. Plus, it could be +present on production systems without debugging support. + +Given appropriate hardware documentation for the system, userspace could +know for example that GPIO #23 controls the write protect line used to +protect boot loader segments in flash memory. System upgrade procedures +may need to temporarily remove that protection, first importing a GPIO, +then changing its output state, then updating the code before re-enabling +the write protection. In normal use, GPIO #23 would never be touched, +and the kernel would have no need to know about it. + +Again depending on appropriate hardware documentation, on some systems +userspace GPIO can be used to determine system configuration data that +standard kernels won't know about. And for some tasks, simple userspace +GPIO drivers could be all that the system really needs. + +Note that standard kernel drivers exist for common "LEDs and Buttons" +GPIO tasks: "leds-gpio" and "gpio_keys", respectively. Use those +instead of talking directly to the GPIOs; they integrate with kernel +frameworks better than your userspace code could. + + +Paths in Sysfs +-------------- +There are three kinds of entry in /sys/class/gpio: + + - Control interfaces used to get userspace control over GPIOs; + + - GPIOs themselves; and + + - GPIO controllers ("gpio_chip" instances). + +That's in addition to standard files including the "device" symlink. + +The control interfaces are write-only: + + /sys/class/gpio/ + + "export" ... Userspace may ask the kernel to export control of + a GPIO to userspace by writing its number to this file. + + Example: "echo 19 > export" will create a "gpio19" node + for GPIO #19, if that's not requested by kernel code. + + "unexport" ... Reverses the effect of exporting to userspace. + + Example: "echo 19 > unexport" will remove a "gpio19" + node exported using the "export" file. + +GPIO signals have paths like /sys/class/gpio/gpio42/ (for GPIO #42) +and have the following read/write attributes: + + /sys/class/gpio/gpioN/ + + "direction" ... reads as either "in" or "out". This value may + normally be written. Writing as "out" defaults to + initializing the value as low. To ensure glitch free + operation, values "low" and "high" may be written to + configure the GPIO as an output with that initial value. + + Note that this attribute *will not exist* if the kernel + doesn't support changing the direction of a GPIO, or + it was exported by kernel code that didn't explicitly + allow userspace to reconfigure this GPIO's direction. + + "value" ... reads as either 0 (low) or 1 (high). If the GPIO + is configured as an output, this value may be written; + any nonzero value is treated as high. + + If the pin can be configured as interrupt-generating interrupt + and if it has been configured to generate interrupts (see the + description of "edge"), you can poll(2) on that file and + poll(2) will return whenever the interrupt was triggered. If + you use poll(2), set the events POLLPRI and POLLERR. If you + use select(2), set the file descriptor in exceptfds. After + poll(2) returns, either lseek(2) to the beginning of the sysfs + file and read the new value or close the file and re-open it + to read the value. + + "edge" ... reads as either "none", "rising", "falling", or + "both". Write these strings to select the signal edge(s) + that will make poll(2) on the "value" file return. + + This file exists only if the pin can be configured as an + interrupt generating input pin. + + "active_low" ... reads as either 0 (false) or 1 (true). Write + any nonzero value to invert the value attribute both + for reading and writing. Existing and subsequent + poll(2) support configuration via the edge attribute + for "rising" and "falling" edges will follow this + setting. + +GPIO controllers have paths like /sys/class/gpio/gpiochip42/ (for the +controller implementing GPIOs starting at #42) and have the following +read-only attributes: + + /sys/class/gpio/gpiochipN/ + + "base" ... same as N, the first GPIO managed by this chip + + "label" ... provided for diagnostics (not always unique) + + "ngpio" ... how many GPIOs this manges (N to N + ngpio - 1) + +Board documentation should in most cases cover what GPIOs are used for +what purposes. However, those numbers are not always stable; GPIOs on +a daughtercard might be different depending on the base board being used, +or other cards in the stack. In such cases, you may need to use the +gpiochip nodes (possibly in conjunction with schematics) to determine +the correct GPIO number to use for a given signal. + + +Exporting from Kernel code +-------------------------- +Kernel code can explicitly manage exports of GPIOs which have already been +requested using gpio_request(): + + /* export the GPIO to userspace */ + int gpiod_export(struct gpio_desc *desc, bool direction_may_change); + + /* reverse gpio_export() */ + void gpiod_unexport(struct gpio_desc *desc); + + /* create a sysfs link to an exported GPIO node */ + int gpiod_export_link(struct device *dev, const char *name, + struct gpio_desc *desc); + + /* change the polarity of a GPIO node in sysfs */ + int gpiod_sysfs_set_active_low(struct gpio_desc *desc, int value); + +After a kernel driver requests a GPIO, it may only be made available in +the sysfs interface by gpiod_export(). The driver can control whether the +signal direction may change. This helps drivers prevent userspace code +from accidentally clobbering important system state. + +This explicit exporting can help with debugging (by making some kinds +of experiments easier), or can provide an always-there interface that's +suitable for documenting as part of a board support package. + +After the GPIO has been exported, gpiod_export_link() allows creating +symlinks from elsewhere in sysfs to the GPIO sysfs node. Drivers can +use this to provide the interface under their own device in sysfs with +a descriptive name. + +Drivers can use gpiod_sysfs_set_active_low() to hide GPIO line polarity +differences between boards from user space. Polarity change can be done both +before and after gpiod_export(), and previously enabled poll(2) support for +either rising or falling edge will be reconfigured to follow this setting. From 79697ef94c48df8831a156bbb046e94215b7300d Mon Sep 17 00:00:00 2001 From: Alexandre Courbot Date: Sat, 16 Nov 2013 21:39:32 +0900 Subject: [PATCH 03/12] gpiolib: fix find_chip_by_name() find_chip_by_name() was incorrectly implemented by using gpio_lookup_list instead of gpiod_chips to iterate through all the registered GPIO controllers. This patch reimplements it by using gpiochip_find() with a custom search function, which simplifies the code on top of fixing the mistake. Signed-off-by: Alexandre Courbot Signed-off-by: Linus Walleij --- drivers/gpio/gpiolib.c | 29 ++++++++++++----------------- 1 file changed, 12 insertions(+), 17 deletions(-) diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index 4e10b10d3ddd..d8938b9b794a 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -1308,6 +1308,18 @@ struct gpio_chip *gpiochip_find(void *data, } EXPORT_SYMBOL_GPL(gpiochip_find); +static int gpiochip_match_name(struct gpio_chip *chip, void *data) +{ + const char *name = data; + + return !strcmp(chip->label, name); +} + +static struct gpio_chip *find_chip_by_name(const char *name) +{ + return gpiochip_find((void *)name, gpiochip_match_name); +} + #ifdef CONFIG_PINCTRL /** @@ -2260,23 +2272,6 @@ void gpiod_add_table(struct gpiod_lookup *table, size_t size) mutex_unlock(&gpio_lookup_lock); } -/* - * Caller must have a acquired gpio_lookup_lock - */ -static struct gpio_chip *find_chip_by_name(const char *name) -{ - struct gpio_chip *chip = NULL; - - list_for_each_entry(chip, &gpio_lookup_list, list) { - if (chip->label == NULL) - continue; - if (!strcmp(chip->label, name)) - break; - } - - return chip; -} - #ifdef CONFIG_OF static struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id, unsigned int idx, unsigned long *flags) From 53e7cac35db5941f42221314c33693e71ffa496b Mon Sep 17 00:00:00 2001 From: Alexandre Courbot Date: Sat, 16 Nov 2013 21:44:52 +0900 Subject: [PATCH 04/12] gpiolib: use dedicated flags for GPIO properties GPIO mapping properties were defined using the GPIOF_* flags, which are declared in linux/gpio.h. This file is not included when using the GPIO descriptor interface. This patch declares the flags that can be used as GPIO mappings properties in linux/gpio/driver.h, and uses them in gpiolib, so that no deprecated declarations are used by the GPIO descriptor interface. This patch also allows GPIO_OPEN_DRAIN and GPIO_OPEN_SOURCE to be specified as GPIO mapping properties. Signed-off-by: Alexandre Courbot Signed-off-by: Linus Walleij --- drivers/gpio/gpiolib.c | 22 +++++++++++++++------- include/linux/gpio/driver.h | 11 +++++++++-- 2 files changed, 24 insertions(+), 9 deletions(-) diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index d8938b9b794a..490198365ce4 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -14,6 +14,7 @@ #include #include #include +#include #define CREATE_TRACE_POINTS #include @@ -2274,7 +2275,8 @@ void gpiod_add_table(struct gpiod_lookup *table, size_t size) #ifdef CONFIG_OF static struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id, - unsigned int idx, unsigned long *flags) + unsigned int idx, + enum gpio_lookup_flags *flags) { char prop_name[32]; /* 32 is max size of property name */ enum of_gpio_flags of_flags; @@ -2292,7 +2294,7 @@ static struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id, return desc; if (of_flags & OF_GPIO_ACTIVE_LOW) - *flags |= GPIOF_ACTIVE_LOW; + *flags |= GPIO_ACTIVE_LOW; return desc; } @@ -2305,7 +2307,8 @@ static struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id, #endif static struct gpio_desc *acpi_find_gpio(struct device *dev, const char *con_id, - unsigned int idx, unsigned long *flags) + unsigned int idx, + enum gpio_lookup_flags *flags) { struct acpi_gpio_info info; struct gpio_desc *desc; @@ -2315,13 +2318,14 @@ static struct gpio_desc *acpi_find_gpio(struct device *dev, const char *con_id, return desc; if (info.gpioint && info.active_low) - *flags |= GPIOF_ACTIVE_LOW; + *flags |= GPIO_ACTIVE_LOW; return desc; } static struct gpio_desc *gpiod_find(struct device *dev, const char *con_id, - unsigned int idx, unsigned long *flags) + unsigned int idx, + enum gpio_lookup_flags *flags) { const char *dev_id = dev ? dev_name(dev) : NULL; struct gpio_desc *desc = ERR_PTR(-ENODEV); @@ -2413,7 +2417,7 @@ struct gpio_desc *__must_check gpiod_get_index(struct device *dev, { struct gpio_desc *desc; int status; - unsigned long flags = 0; + enum gpio_lookup_flags flags = 0; dev_dbg(dev, "GPIO lookup for consumer %s\n", con_id); @@ -2439,8 +2443,12 @@ struct gpio_desc *__must_check gpiod_get_index(struct device *dev, if (status < 0) return ERR_PTR(status); - if (flags & GPIOF_ACTIVE_LOW) + if (flags & GPIO_ACTIVE_LOW) set_bit(FLAG_ACTIVE_LOW, &desc->flags); + if (flags & GPIO_OPEN_DRAIN) + set_bit(FLAG_OPEN_DRAIN, &desc->flags); + if (flags & GPIO_OPEN_SOURCE) + set_bit(FLAG_OPEN_SOURCE, &desc->flags); return desc; } diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h index 656a27efb2c8..82eac610ce1a 100644 --- a/include/linux/gpio/driver.h +++ b/include/linux/gpio/driver.h @@ -125,6 +125,13 @@ extern struct gpio_chip *gpiochip_find(void *data, int gpiod_lock_as_irq(struct gpio_desc *desc); void gpiod_unlock_as_irq(struct gpio_desc *desc); +enum gpio_lookup_flags { + GPIO_ACTIVE_HIGH = (0 << 0), + GPIO_ACTIVE_LOW = (1 << 0), + GPIO_OPEN_DRAIN = (1 << 1), + GPIO_OPEN_SOURCE = (1 << 2), +}; + /** * Lookup table for associating GPIOs to specific devices and functions using * platform data. @@ -152,9 +159,9 @@ struct gpiod_lookup { */ unsigned int idx; /* - * mask of GPIOF_* values + * mask of GPIO_* values */ - unsigned long flags; + enum gpio_lookup_flags flags; }; /* From d535922691fc026479fcc03e78ac3d931a54e75a Mon Sep 17 00:00:00 2001 From: Dan Carpenter Date: Thu, 7 Nov 2013 10:50:19 +0300 Subject: [PATCH 05/12] gpio: mvebu: make mvchip->irqbase signed for error handling There is a bug in mvebu_gpio_probe() where we do: mvchip->irqbase = irq_alloc_descs(-1, 0, ngpios, -1); if (mvchip->irqbase < 0) { The problem is that mvchip->irqbase is unsigned so the error handling doesn't work. I have changed it to be a regular int. Cc: stable@vger.kernel.org Signed-off-by: Dan Carpenter Signed-off-by: Linus Walleij --- drivers/gpio/gpio-mvebu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpio/gpio-mvebu.c b/drivers/gpio/gpio-mvebu.c index 3c3321f94053..db3129043e63 100644 --- a/drivers/gpio/gpio-mvebu.c +++ b/drivers/gpio/gpio-mvebu.c @@ -79,7 +79,7 @@ struct mvebu_gpio_chip { spinlock_t lock; void __iomem *membase; void __iomem *percpu_membase; - unsigned int irqbase; + int irqbase; struct irq_domain *domain; int soc_variant; }; From bfea603bc54c0a736d45bc60b188a8cdae9aaaa3 Mon Sep 17 00:00:00 2001 From: Dan Carpenter Date: Thu, 7 Nov 2013 10:51:34 +0300 Subject: [PATCH 06/12] gpio: msm: make msm_gpio.summary_irq signed for error handling There is a bug in msm_gpio_probe() where we do: msm_gpio.summary_irq = platform_get_irq(pdev, 0); if (msm_gpio.summary_irq < 0) { The problem is that "msm_gpio.summary_irq" is unsigned so the error handling doesn't work. I've fixed it by making it signed. Fixes: 43f68444bce7 ('gpio: msm: Add device tree and irqdomain support for gpio-msm-v2') Cc: stable@vger.kernel.org Signed-off-by: Dan Carpenter Signed-off-by: Linus Walleij --- drivers/gpio/gpio-msm-v2.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpio/gpio-msm-v2.c b/drivers/gpio/gpio-msm-v2.c index f7a0cc4da950..7b37300973db 100644 --- a/drivers/gpio/gpio-msm-v2.c +++ b/drivers/gpio/gpio-msm-v2.c @@ -102,7 +102,7 @@ struct msm_gpio_dev { DECLARE_BITMAP(wake_irqs, MAX_NR_GPIO); DECLARE_BITMAP(dual_edge_irqs, MAX_NR_GPIO); struct irq_domain *domain; - unsigned int summary_irq; + int summary_irq; void __iomem *msm_tlmm_base; }; From 0c8aab8e65e450f2bfea494c1b6a86ded653f88c Mon Sep 17 00:00:00 2001 From: Dan Carpenter Date: Thu, 7 Nov 2013 10:56:51 +0300 Subject: [PATCH 07/12] gpio: rcar: NULL dereference on error in probe() It's not obvious from the label name but "err1" tries to release "p->irq_domain" which leads to a NULL dereference. Fixes: 119f5e448d32 ('gpio: Renesas R-Car GPIO driver V3') Cc: stable@vger.kernel.org Signed-off-by: Dan Carpenter Acked-by: Magnus Damm Signed-off-by: Linus Walleij --- drivers/gpio/gpio-rcar.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpio/gpio-rcar.c b/drivers/gpio/gpio-rcar.c index d3f15ae93bd3..fe088a30567a 100644 --- a/drivers/gpio/gpio-rcar.c +++ b/drivers/gpio/gpio-rcar.c @@ -381,7 +381,7 @@ static int gpio_rcar_probe(struct platform_device *pdev) if (!p->irq_domain) { ret = -ENXIO; dev_err(&pdev->dev, "cannot initialize irq domain\n"); - goto err1; + goto err0; } if (devm_request_irq(&pdev->dev, irq->start, From 61c6375d55235e67d15b4a12cfe90d02710cef5e Mon Sep 17 00:00:00 2001 From: Michal Nazarewicz Date: Wed, 13 Nov 2013 21:20:39 +0100 Subject: [PATCH 08/12] gpio: fix memory leak in error path Signed-off-by: Michal Nazarewicz Signed-off-by: Linus Walleij --- drivers/gpio/gpiolib.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index 490198365ce4..14ab16fbaad5 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -1354,8 +1354,10 @@ int gpiochip_add_pingroup_range(struct gpio_chip *chip, ret = pinctrl_get_group_pins(pctldev, pin_group, &pin_range->range.pins, &pin_range->range.npins); - if (ret < 0) + if (ret < 0) { + kfree(pin_range); return ret; + } pinctrl_add_gpio_range(pctldev, &pin_range->range); From 209e64f9ed28e4e686c3dfb0ed89069849d679c6 Mon Sep 17 00:00:00 2001 From: Alexandre Courbot Date: Tue, 19 Nov 2013 10:37:29 +0900 Subject: [PATCH 09/12] gpiolib: fix of_find_gpio() when OF not defined The prototype for static GPIO lookup functions has been updated to use an explicit type for GPIO lookup flags. Unfortunately the definition of of_find_gpio() when CONFIG_OF is not defined has been omitted, which triggers a warning. This patch fixes this. Signed-off-by: Alexandre Courbot Signed-off-by: Linus Walleij --- drivers/gpio/gpiolib.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index 14ab16fbaad5..ac53a9593662 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -2302,7 +2302,8 @@ static struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id, } #else static struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id, - unsigned int idx, unsigned long *flags) + unsigned int idx, + enum gpio_lookup_flags *flags) { return ERR_PTR(-ENODEV); } From 41ad730e5d2cbad29e64764db2929707a4a883e2 Mon Sep 17 00:00:00 2001 From: Axel Lin Date: Tue, 19 Nov 2013 15:31:20 +0800 Subject: [PATCH 10/12] gpio: ucb1400: Add MODULE_ALIAS This driver can be built as a module now. Add MODULE_ALIAS to support module auto-loading. Signed-off-by: Axel Lin Reviewed-by: Jean Delvare Signed-off-by: Linus Walleij --- drivers/gpio/gpio-ucb1400.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/gpio/gpio-ucb1400.c b/drivers/gpio/gpio-ucb1400.c index 1a605f2a0f55..06fb5cf99ded 100644 --- a/drivers/gpio/gpio-ucb1400.c +++ b/drivers/gpio/gpio-ucb1400.c @@ -105,3 +105,4 @@ module_platform_driver(ucb1400_gpio_driver); MODULE_DESCRIPTION("Philips UCB1400 GPIO driver"); MODULE_LICENSE("GPL"); +MODULE_ALIAS("platform:ucb1400_gpio"); From 2ba3154d9cb13697b97723cce75633b48adfe826 Mon Sep 17 00:00:00 2001 From: Linus Walleij Date: Wed, 27 Nov 2013 08:47:02 +0100 Subject: [PATCH 11/12] gpio: pl061: move irqdomain initialization The PL061 driver had the irqdomain initialization in an unfortunate place: when used with device tree (and thus passing the base IRQ 0) the driver would work, as this registers an irqdomain and waits for mappings to be done dynamically as the devices request their IRQs, whereas when booting using platform data the irqdomain core would attempt to allocate IRQ descriptors dynamically (which works fine) but also to associate the irq_domain_associate_many() on all IRQs, which in turn will call the mapping function which at this point will try to set the type of the IRQ and then tries to acquire a non-initialized spinlock yielding a backtrace like this: CPU: 0 PID: 1 Comm: swapper Not tainted 3.13.0-rc1+ #652 Backtrace: [] (dump_backtrace) from [] (show_stack+0x18/0x1c) r6:c798ace0 r5:00000000 r4:c78257e0 r3:00200140 [] (show_stack) from [] (dump_stack+0x20/0x28) [] (dump_stack) from [] (__lock_acquire+0x1c0/0x1b80) [] (__lock_acquire) from [] (lock_acquire+0x6c/0x80) r10:00000000 r9:c0455234 r8:00000060 r7:c047d798 r6:600000d3 r5:00000000 r4:c782c000 [] (lock_acquire) from [] (_raw_spin_lock_irqsave+0x60/0x74) r6:c01a1100 r5:800000d3 r4:c798acd0 [] (_raw_spin_lock_irqsave) from [] (pl061_irq_type+0x28/0x) r6:00000000 r5:00000000 r4:c798acd0 [] (pl061_irq_type) from [] (__irq_set_trigger+0x70/0x104) r6:00000000 r5:c01a10d8 r4:c046da1c r3:c01a10d8 [] (__irq_set_trigger) from [] (irq_set_irq_type+0x40/0x60) r10:c043240c r8:00000060 r7:00000000 r6:c046da1c r5:00000060 r4:00000000 [] (irq_set_irq_type) from [] (pl061_irq_map+0x40/0x54) r6:c79693c0 r5:c798acd0 r4:00000060 [] (pl061_irq_map) from [] (irq_domain_associate+0xc0/0x190) r5:00000060 r4:c046da1c [] (irq_domain_associate) from [] (irq_domain_associate_man) r8:00000008 r7:00000000 r6:c79693c0 r5:00000060 r4:00000000 [] (irq_domain_associate_many) from [] (irq_domain_add_simp) r8:c046578c r7:c035b72c r6:c79693c0 r5:00000060 r4:00000008 r3:00000008 [] (irq_domain_add_simple) from [] (pl061_probe+0xc4/0x22c) r6:00000060 r5:c0464380 r4:c798acd0 [] (pl061_probe) from [] (amba_probe+0x74/0xe0) r10:c043240c r9:c0455234 r8:00000000 r7:c047d7f8 r6:c047d744 r5:00000000 r4:c0464380 This moves the irqdomain initialization to a point where the spinlock and GPIO chip are both fully propulated, so the callbacks can be used without crashes. I had some problem reproducing the crash, as the devm_kzalloc():ed zeroed memory would seemingly mask the spinlock as something OK, but by poisoning the lock like this: u32 *dum; dum = (u32 *) &chip->lock; *dum = 0xaaaaaaaaU; I could reproduce, fix and test the patch. Reported-by: Russell King Cc: Rob Herring Cc: Haojian Zhuang Cc: Baruch Siach Signed-off-by: Linus Walleij --- drivers/gpio/gpio-pl061.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/drivers/gpio/gpio-pl061.c b/drivers/gpio/gpio-pl061.c index f22f7f3e2e53..b4d42112d02d 100644 --- a/drivers/gpio/gpio-pl061.c +++ b/drivers/gpio/gpio-pl061.c @@ -286,11 +286,6 @@ static int pl061_probe(struct amba_device *adev, const struct amba_id *id) if (!chip->base) return -ENOMEM; - chip->domain = irq_domain_add_simple(adev->dev.of_node, PL061_GPIO_NR, - irq_base, &pl061_domain_ops, chip); - if (!chip->domain) - return -ENODEV; - spin_lock_init(&chip->lock); chip->gc.request = pl061_gpio_request; @@ -320,6 +315,11 @@ static int pl061_probe(struct amba_device *adev, const struct amba_id *id) irq_set_chained_handler(irq, pl061_irq_handler); irq_set_handler_data(irq, chip); + chip->domain = irq_domain_add_simple(adev->dev.of_node, PL061_GPIO_NR, + irq_base, &pl061_domain_ops, chip); + if (!chip->domain) + return -ENODEV; + for (i = 0; i < PL061_GPIO_NR; i++) { if (pdata) { if (pdata->directions & (1 << i)) From e2f0b00560729c47f39b2bc624eb93d82dc0e3e8 Mon Sep 17 00:00:00 2001 From: Markus Mayer Date: Thu, 21 Nov 2013 15:12:46 -0800 Subject: [PATCH 12/12] gpio: bcm281xx: Fix return value of bcm_kona_gpio_get() We need to return the corresponding bit for a particular GPIO. This bit contains shift not mask. Signed-off-by: Markus Mayer Reviewed-by: Tim Kryger Reviewed-by: Matt Porter Signed-off-by: Linus Walleij --- drivers/gpio/gpio-bcm-kona.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpio/gpio-bcm-kona.c b/drivers/gpio/gpio-bcm-kona.c index 72c927dc3be1..54c18c220a60 100644 --- a/drivers/gpio/gpio-bcm-kona.c +++ b/drivers/gpio/gpio-bcm-kona.c @@ -158,7 +158,7 @@ static int bcm_kona_gpio_get(struct gpio_chip *chip, unsigned gpio) spin_unlock_irqrestore(&kona_gpio->lock, flags); /* return the specified bit status */ - return !!(val & bit); + return !!(val & BIT(bit)); } static int bcm_kona_gpio_direction_input(struct gpio_chip *chip, unsigned gpio)