LEDS: tca6507 - fix up some comments.
In particular fix the capitalisation of GPIO and LED and correct TCA6507_MAKE_CPIO, but also rewrite the comment about platform-data to include reference to devicetree. Also re-wrap comments to fit 80 columns. Reported-by: Bryan Wu <cooloney@gmail.com> Signed-off-by: NeilBrown <neilb@suse.de> Signed-off-by: Bryan Wu <cooloney@gmail.com>
This commit is contained in:
NeilBrown
Bryan Wu
parent
10ead6e599
commit
1f431afdb4
1 changed files with 101 additions and 87 deletions
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@ -4,77 +4,87 @@
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* The TCA6507 is a programmable LED controller that can drive 7
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* separate lines either by holding them low, or by pulsing them
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* with modulated width.
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* The modulation can be varied in a simple pattern to produce a blink or
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* double-blink.
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* The modulation can be varied in a simple pattern to produce a
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* blink or double-blink.
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*
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* This driver can configure each line either as a 'GPIO' which is out-only
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* (no pull-up) or as an LED with variable brightness and hardware-assisted
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* blinking.
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* This driver can configure each line either as a 'GPIO' which is
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* out-only (pull-up resistor required) or as an LED with variable
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* brightness and hardware-assisted blinking.
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*
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* Apart from OFF and ON there are three programmable brightness levels which
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* can be programmed from 0 to 15 and indicate how many 500usec intervals in
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* each 8msec that the led is 'on'. The levels are named MASTER, BANK0 and
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* BANK1.
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* Apart from OFF and ON there are three programmable brightness
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* levels which can be programmed from 0 to 15 and indicate how many
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* 500usec intervals in each 8msec that the led is 'on'. The levels
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* are named MASTER, BANK0 and BANK1.
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*
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* There are two different blink rates that can be programmed, each with
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* separate time for rise, on, fall, off and second-off. Thus if 3 or more
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* different non-trivial rates are required, software must be used for the extra
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* rates. The two different blink rates must align with the two levels BANK0 and
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* BANK1.
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* This driver does not support double-blink so 'second-off' always matches
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* 'off'.
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* There are two different blink rates that can be programmed, each
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* with separate time for rise, on, fall, off and second-off. Thus if
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* 3 or more different non-trivial rates are required, software must
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* be used for the extra rates. The two different blink rates must
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* align with the two levels BANK0 and BANK1. This driver does not
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* support double-blink so 'second-off' always matches 'off'.
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*
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* Only 16 different times can be programmed in a roughly logarithmic scale from
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* 64ms to 16320ms. To be precise the possible times are:
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* Only 16 different times can be programmed in a roughly logarithmic
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* scale from 64ms to 16320ms. To be precise the possible times are:
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* 0, 64, 128, 192, 256, 384, 512, 768,
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* 1024, 1536, 2048, 3072, 4096, 5760, 8128, 16320
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*
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* Times that cannot be closely matched with these must be
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* handled in software. This driver allows 12.5% error in matching.
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* Times that cannot be closely matched with these must be handled in
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* software. This driver allows 12.5% error in matching.
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*
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* This driver does not allow rise/fall rates to be set explicitly. When trying
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* to match a given 'on' or 'off' period, an appropriate pair of 'change' and
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* 'hold' times are chosen to get a close match. If the target delay is even,
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* the 'change' number will be the smaller; if odd, the 'hold' number will be
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* the smaller.
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* This driver does not allow rise/fall rates to be set explicitly.
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* When trying to match a given 'on' or 'off' period, an appropriate
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* pair of 'change' and 'hold' times are chosen to get a close match.
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* If the target delay is even, the 'change' number will be the
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* smaller; if odd, the 'hold' number will be the smaller.
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* Choosing pairs of delays with 12.5% errors allows us to match delays in the
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* ranges: 56-72, 112-144, 168-216, 224-27504, 28560-36720.
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* 26% of the achievable sums can be matched by multiple pairings. For example
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* 1536 == 1536+0, 1024+512, or 768+768. This driver will always choose the
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* pairing with the least maximum - 768+768 in this case. Other pairings are
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* not available.
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* Choosing pairs of delays with 12.5% errors allows us to match
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* delays in the ranges: 56-72, 112-144, 168-216, 224-27504,
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* 28560-36720.
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* 26% of the achievable sums can be matched by multiple pairings.
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* For example 1536 == 1536+0, 1024+512, or 768+768.
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* This driver will always choose the pairing with the least
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* maximum - 768+768 in this case. Other pairings are not available.
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*
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* Access to the 3 levels and 2 blinks are on a first-come, first-served basis.
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* Access can be shared by multiple leds if they have the same level and
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* either same blink rates, or some don't blink.
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* When a led changes, it relinquishes access and tries again, so it might
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* lose access to hardware blink.
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* If a blink engine cannot be allocated, software blink is used.
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* If the desired brightness cannot be allocated, the closest available non-zero
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* brightness is used. As 'full' is always available, the worst case would be
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* to have two different blink rates at '1', with Max at '2', then other leds
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* will have to choose between '2' and '16'. Hopefully this is not likely.
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* Access to the 3 levels and 2 blinks are on a first-come,
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* first-served basis. Access can be shared by multiple leds if they
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* have the same level and either same blink rates, or some don't
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* blink. When a led changes, it relinquishes access and tries again,
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* so it might lose access to hardware blink.
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*
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* Each bank (BANK0 and BANK1) has two usage counts - LEDs using the brightness
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* and LEDs using the blink. It can only be reprogrammed when the appropriate
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* counter is zero. The MASTER level has a single usage count.
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* If a blink engine cannot be allocated, software blink is used. If
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* the desired brightness cannot be allocated, the closest available
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* non-zero brightness is used. As 'full' is always available, the
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* worst case would be to have two different blink rates at '1', with
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* Max at '2', then other leds will have to choose between '2' and
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* '16'. Hopefully this is not likely.
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*
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* Each Led has programmable 'on' and 'off' time as milliseconds. With each
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* there is a flag saying if it was explicitly requested or defaulted.
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* Similarly the banks know if each time was explicit or a default. Defaults
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* are permitted to be changed freely - they are not recognised when matching.
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* Each bank (BANK0 and BANK1) has two usage counts - LEDs using the
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* brightness and LEDs using the blink. It can only be reprogrammed
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* when the appropriate counter is zero. The MASTER level has a
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* single usage count.
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*
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* Each LED has programmable 'on' and 'off' time as milliseconds.
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* With each there is a flag saying if it was explicitly requested or
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* defaulted. Similarly the banks know if each time was explicit or a
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* default. Defaults are permitted to be changed freely - they are
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* not recognised when matching.
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*
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*
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* An led-tca6507 device must be provided with platform data. This data
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* lists for each output: the name, default trigger, and whether the signal
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* is being used as a GPiO rather than an led. 'struct led_plaform_data'
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* is used for this. If 'name' is NULL, the output isn't used. If 'flags'
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* is TCA6507_MAKE_CPIO, the output is a GPO.
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* The "struct led_platform_data" can be embedded in a
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* "struct tca6507_platform_data" which adds a 'gpio_base' for the GPiOs,
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* and a 'setup' callback which is called once the GPiOs are available.
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* An led-tca6507 device must be provided with platform data or
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* configured via devicetree.
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*
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* The platform-data lists for each output: the name, default trigger,
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* and whether the signal is being used as a GPIO rather than an LED.
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* 'struct led_plaform_data' is used for this. If 'name' is NULL, the
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* output isn't used. If 'flags' is TCA6507_MAKE_GPIO, the output is
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* a GPO. The "struct led_platform_data" can be embedded in a "struct
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* tca6507_platform_data" which adds a 'gpio_base' for the GPIOs, and
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* a 'setup' callback which is called once the GPIOs are available.
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*
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* When configured via devicetree there is one child for each output.
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* The "reg" determines the output number and "compatible" determines
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* whether it is an LED or a GPIO. "linux,default-trigger" can set a
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* default trigger.
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*/
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#include <linux/module.h>
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@ -192,17 +202,18 @@ MODULE_DEVICE_TABLE(i2c, tca6507_id);
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static int choose_times(int msec, int *c1p, int *c2p)
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{
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/*
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* Choose two timecodes which add to 'msec' as near as possible.
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* The first returned is the 'on' or 'off' time. The second is to be
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* used as a 'fade-on' or 'fade-off' time. If 'msec' is even,
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* the first will not be smaller than the second. If 'msec' is odd,
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* the first will not be larger than the second.
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* If we cannot get a sum within 1/8 of 'msec' fail with -EINVAL,
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* otherwise return the sum that was achieved, plus 1 if the first is
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* smaller.
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* If two possibilities are equally good (e.g. 512+0, 256+256), choose
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* the first pair so there is more change-time visible (i.e. it is
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* softer).
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* Choose two timecodes which add to 'msec' as near as
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* possible. The first returned is the 'on' or 'off' time.
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* The second is to be used as a 'fade-on' or 'fade-off' time.
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* If 'msec' is even, the first will not be smaller than the
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* second. If 'msec' is odd, the first will not be larger
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* than the second.
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* If we cannot get a sum within 1/8 of 'msec' fail with
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* -EINVAL, otherwise return the sum that was achieved, plus 1
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* if the first is smaller.
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* If two possibilities are equally good (e.g. 512+0,
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* 256+256), choose the first pair so there is more
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* change-time visible (i.e. it is softer).
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*/
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int c1, c2;
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int tmax = msec * 9 / 8;
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@ -255,8 +266,8 @@ static int choose_times(int msec, int *c1p, int *c2p)
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}
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/*
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* Update the register file with the appropriate 3-bit state for
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* the given led.
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* Update the register file with the appropriate 3-bit state for the
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* given led.
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*/
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static void set_select(struct tca6507_chip *tca, int led, int val)
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{
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@ -274,9 +285,9 @@ static void set_select(struct tca6507_chip *tca, int led, int val)
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}
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}
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/* Update the register file with the appropriate 4-bit code for
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* one bank or other. This can be used for timers, for levels, or
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* for initialisation.
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/* Update the register file with the appropriate 4-bit code for one
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* bank or other. This can be used for timers, for levels, or for
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* initialization.
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*/
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static void set_code(struct tca6507_chip *tca, int reg, int bank, int new)
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{
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@ -309,7 +320,7 @@ static void set_level(struct tca6507_chip *tca, int bank, int level)
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tca->bank[bank].level = level;
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}
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/* Record all relevant time code for a given bank */
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/* Record all relevant time codes for a given bank */
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static void set_times(struct tca6507_chip *tca, int bank)
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{
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int c1, c2;
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@ -317,7 +328,8 @@ static void set_times(struct tca6507_chip *tca, int bank)
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result = choose_times(tca->bank[bank].ontime, &c1, &c2);
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dev_dbg(&tca->client->dev,
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"Chose on times %d(%d) %d(%d) for %dms\n", c1, time_codes[c1],
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"Chose on times %d(%d) %d(%d) for %dms\n",
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c1, time_codes[c1],
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c2, time_codes[c2], tca->bank[bank].ontime);
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set_code(tca, TCA6507_FADE_ON, bank, c2);
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set_code(tca, TCA6507_FULL_ON, bank, c1);
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@ -325,7 +337,8 @@ static void set_times(struct tca6507_chip *tca, int bank)
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result = choose_times(tca->bank[bank].offtime, &c1, &c2);
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dev_dbg(&tca->client->dev,
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"Chose off times %d(%d) %d(%d) for %dms\n", c1, time_codes[c1],
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"Chose off times %d(%d) %d(%d) for %dms\n",
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c1, time_codes[c1],
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c2, time_codes[c2], tca->bank[bank].offtime);
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set_code(tca, TCA6507_FADE_OFF, bank, c2);
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set_code(tca, TCA6507_FIRST_OFF, bank, c1);
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@ -373,7 +386,8 @@ static void led_release(struct tca6507_led *led)
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static int led_prepare(struct tca6507_led *led)
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{
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/* Assign this led to a bank, configuring that bank if necessary. */
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/* Assign this led to a bank, configuring that bank if
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* necessary. */
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int level = TO_LEVEL(led->led_cdev.brightness);
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struct tca6507_chip *tca = led->chip;
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int c1, c2;
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@ -389,10 +403,10 @@ static int led_prepare(struct tca6507_led *led)
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if (led->ontime == 0 || led->offtime == 0) {
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/*
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* Just set the brightness, choosing first usable bank.
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* If none perfect, choose best.
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* Count backwards so we check MASTER bank first
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* to avoid wasting a timer.
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* Just set the brightness, choosing first usable
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* bank. If none perfect, choose best. Count
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* backwards so we check MASTER bank first to avoid
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* wasting a timer.
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*/
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int best = -1;/* full-on */
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int diff = 15-level;
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@ -433,9 +447,9 @@ static int led_prepare(struct tca6507_led *led)
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}
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/*
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* We have on/off time so we need to try to allocate a timing bank.
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* First check if times are compatible with hardware and give up if
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* not.
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* We have on/off time so we need to try to allocate a timing
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* bank. First check if times are compatible with hardware
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* and give up if not.
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*/
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if (choose_times(led->ontime, &c1, &c2) < 0)
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return -EINVAL;
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@ -523,8 +537,8 @@ static int led_assign(struct tca6507_led *led)
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err = led_prepare(led);
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if (err) {
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/*
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* Can only fail on timer setup. In that case we need to
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* re-establish as steady level.
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* Can only fail on timer setup. In that case we need
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* to re-establish as steady level.
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*/
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led->ontime = 0;
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led->offtime = 0;
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@ -594,8 +608,8 @@ static void tca6507_gpio_set_value(struct gpio_chip *gc,
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spin_lock_irqsave(&tca->lock, flags);
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/*
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* 'OFF' is floating high, and 'ON' is pulled down, so it has the
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* inverse sense of 'val'.
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* 'OFF' is floating high, and 'ON' is pulled down, so it has
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* the inverse sense of 'val'.
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*/
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set_select(tca, tca->gpio_map[offset],
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val ? TCA6507_LS_LED_OFF : TCA6507_LS_LED_ON);
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