kernel-fxtec-pro1x/arch/cris/arch-v32/drivers/gpio.c
Eric Sesterhenn 32ea086b7b [PATCH] cris: switch to iminor/imajor
Signed-off-by: Eric Sesterhenn <snakebyte@gmx.de>
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Mikael Starvik <starvik@axis.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-07-10 13:24:22 -07:00

765 lines
19 KiB
C

/* $Id: gpio.c,v 1.16 2005/06/19 17:06:49 starvik Exp $
*
* ETRAX CRISv32 general port I/O device
*
* Copyright (c) 1999, 2000, 2001, 2002, 2003 Axis Communications AB
*
* Authors: Bjorn Wesen (initial version)
* Ola Knutsson (LED handling)
* Johan Adolfsson (read/set directions, write, port G,
* port to ETRAX FS.
*
* $Log: gpio.c,v $
* Revision 1.16 2005/06/19 17:06:49 starvik
* Merge of Linux 2.6.12.
*
* Revision 1.15 2005/05/25 08:22:20 starvik
* Changed GPIO port order to fit packages/devices/axis-2.4.
*
* Revision 1.14 2005/04/24 18:35:08 starvik
* Updated with final register headers.
*
* Revision 1.13 2005/03/15 15:43:00 starvik
* dev_id needs to be supplied for shared IRQs.
*
* Revision 1.12 2005/03/10 17:12:00 starvik
* Protect alarm list with spinlock.
*
* Revision 1.11 2005/01/05 06:08:59 starvik
* No need to do local_irq_disable after local_irq_save.
*
* Revision 1.10 2004/11/19 08:38:31 starvik
* Removed old crap.
*
* Revision 1.9 2004/05/14 07:58:02 starvik
* Merge of changes from 2.4
*
* Revision 1.8 2003/09/11 07:29:50 starvik
* Merge of Linux 2.6.0-test5
*
* Revision 1.7 2003/07/10 13:25:46 starvik
* Compiles for 2.5.74
* Lindented ethernet.c
*
* Revision 1.6 2003/07/04 08:27:46 starvik
* Merge of Linux 2.5.74
*
* Revision 1.5 2003/06/10 08:26:37 johana
* Etrax -> ETRAX CRISv32
*
* Revision 1.4 2003/06/05 14:22:48 johana
* Initialise some_alarms.
*
* Revision 1.3 2003/06/05 10:15:46 johana
* New INTR_VECT macros.
* Enable interrupts in global config.
*
* Revision 1.2 2003/06/03 15:52:50 johana
* Initial CRIS v32 version.
*
* Revision 1.1 2003/06/03 08:53:15 johana
* Copy of os/lx25/arch/cris/arch-v10/drivers/gpio.c version 1.7.
*
*/
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/ioport.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/string.h>
#include <linux/poll.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <asm/etraxgpio.h>
#include <asm/arch/hwregs/reg_map.h>
#include <asm/arch/hwregs/reg_rdwr.h>
#include <asm/arch/hwregs/gio_defs.h>
#include <asm/arch/hwregs/intr_vect_defs.h>
#include <asm/io.h>
#include <asm/system.h>
#include <asm/irq.h>
/* The following gio ports on ETRAX FS is available:
* pa 8 bits, supports interrupts off, hi, low, set, posedge, negedge anyedge
* pb 18 bits
* pc 18 bits
* pd 18 bits
* pe 18 bits
* each port has a rw_px_dout, r_px_din and rw_px_oe register.
*/
#define GPIO_MAJOR 120 /* experimental MAJOR number */
#define D(x)
#if 0
static int dp_cnt;
#define DP(x) do { dp_cnt++; if (dp_cnt % 1000 == 0) x; }while(0)
#else
#define DP(x)
#endif
static char gpio_name[] = "etrax gpio";
#if 0
static wait_queue_head_t *gpio_wq;
#endif
static int gpio_ioctl(struct inode *inode, struct file *file,
unsigned int cmd, unsigned long arg);
static ssize_t gpio_write(struct file * file, const char * buf, size_t count,
loff_t *off);
static int gpio_open(struct inode *inode, struct file *filp);
static int gpio_release(struct inode *inode, struct file *filp);
static unsigned int gpio_poll(struct file *filp, struct poll_table_struct *wait);
/* private data per open() of this driver */
struct gpio_private {
struct gpio_private *next;
/* The IO_CFG_WRITE_MODE_VALUE only support 8 bits: */
unsigned char clk_mask;
unsigned char data_mask;
unsigned char write_msb;
unsigned char pad1;
/* These fields are generic */
unsigned long highalarm, lowalarm;
wait_queue_head_t alarm_wq;
int minor;
};
/* linked list of alarms to check for */
static struct gpio_private *alarmlist = 0;
static int gpio_some_alarms = 0; /* Set if someone uses alarm */
static unsigned long gpio_pa_high_alarms = 0;
static unsigned long gpio_pa_low_alarms = 0;
static DEFINE_SPINLOCK(alarm_lock);
#define NUM_PORTS (GPIO_MINOR_LAST+1)
#define GIO_REG_RD_ADDR(reg) (volatile unsigned long*) (regi_gio + REG_RD_ADDR_gio_##reg )
#define GIO_REG_WR_ADDR(reg) (volatile unsigned long*) (regi_gio + REG_RD_ADDR_gio_##reg )
unsigned long led_dummy;
static volatile unsigned long *data_out[NUM_PORTS] = {
GIO_REG_WR_ADDR(rw_pa_dout),
GIO_REG_WR_ADDR(rw_pb_dout),
&led_dummy,
GIO_REG_WR_ADDR(rw_pc_dout),
GIO_REG_WR_ADDR(rw_pd_dout),
GIO_REG_WR_ADDR(rw_pe_dout),
};
static volatile unsigned long *data_in[NUM_PORTS] = {
GIO_REG_RD_ADDR(r_pa_din),
GIO_REG_RD_ADDR(r_pb_din),
&led_dummy,
GIO_REG_RD_ADDR(r_pc_din),
GIO_REG_RD_ADDR(r_pd_din),
GIO_REG_RD_ADDR(r_pe_din),
};
static unsigned long changeable_dir[NUM_PORTS] = {
CONFIG_ETRAX_PA_CHANGEABLE_DIR,
CONFIG_ETRAX_PB_CHANGEABLE_DIR,
0,
CONFIG_ETRAX_PC_CHANGEABLE_DIR,
CONFIG_ETRAX_PD_CHANGEABLE_DIR,
CONFIG_ETRAX_PE_CHANGEABLE_DIR,
};
static unsigned long changeable_bits[NUM_PORTS] = {
CONFIG_ETRAX_PA_CHANGEABLE_BITS,
CONFIG_ETRAX_PB_CHANGEABLE_BITS,
0,
CONFIG_ETRAX_PC_CHANGEABLE_BITS,
CONFIG_ETRAX_PD_CHANGEABLE_BITS,
CONFIG_ETRAX_PE_CHANGEABLE_BITS,
};
static volatile unsigned long *dir_oe[NUM_PORTS] = {
GIO_REG_WR_ADDR(rw_pa_oe),
GIO_REG_WR_ADDR(rw_pb_oe),
&led_dummy,
GIO_REG_WR_ADDR(rw_pc_oe),
GIO_REG_WR_ADDR(rw_pd_oe),
GIO_REG_WR_ADDR(rw_pe_oe),
};
static unsigned int
gpio_poll(struct file *file,
poll_table *wait)
{
unsigned int mask = 0;
struct gpio_private *priv = (struct gpio_private *)file->private_data;
unsigned long data;
poll_wait(file, &priv->alarm_wq, wait);
if (priv->minor == GPIO_MINOR_A) {
reg_gio_rw_intr_cfg intr_cfg;
unsigned long tmp;
unsigned long flags;
local_irq_save(flags);
data = REG_TYPE_CONV(unsigned long, reg_gio_r_pa_din, REG_RD(gio, regi_gio, r_pa_din));
/* PA has support for interrupt
* lets activate high for those low and with highalarm set
*/
intr_cfg = REG_RD(gio, regi_gio, rw_intr_cfg);
tmp = ~data & priv->highalarm & 0xFF;
if (tmp & (1 << 0)) {
intr_cfg.pa0 = regk_gio_hi;
}
if (tmp & (1 << 1)) {
intr_cfg.pa1 = regk_gio_hi;
}
if (tmp & (1 << 2)) {
intr_cfg.pa2 = regk_gio_hi;
}
if (tmp & (1 << 3)) {
intr_cfg.pa3 = regk_gio_hi;
}
if (tmp & (1 << 4)) {
intr_cfg.pa4 = regk_gio_hi;
}
if (tmp & (1 << 5)) {
intr_cfg.pa5 = regk_gio_hi;
}
if (tmp & (1 << 6)) {
intr_cfg.pa6 = regk_gio_hi;
}
if (tmp & (1 << 7)) {
intr_cfg.pa7 = regk_gio_hi;
}
/*
* lets activate low for those high and with lowalarm set
*/
tmp = data & priv->lowalarm & 0xFF;
if (tmp & (1 << 0)) {
intr_cfg.pa0 = regk_gio_lo;
}
if (tmp & (1 << 1)) {
intr_cfg.pa1 = regk_gio_lo;
}
if (tmp & (1 << 2)) {
intr_cfg.pa2 = regk_gio_lo;
}
if (tmp & (1 << 3)) {
intr_cfg.pa3 = regk_gio_lo;
}
if (tmp & (1 << 4)) {
intr_cfg.pa4 = regk_gio_lo;
}
if (tmp & (1 << 5)) {
intr_cfg.pa5 = regk_gio_lo;
}
if (tmp & (1 << 6)) {
intr_cfg.pa6 = regk_gio_lo;
}
if (tmp & (1 << 7)) {
intr_cfg.pa7 = regk_gio_lo;
}
REG_WR(gio, regi_gio, rw_intr_cfg, intr_cfg);
local_irq_restore(flags);
} else if (priv->minor <= GPIO_MINOR_E)
data = *data_in[priv->minor];
else
return 0;
if ((data & priv->highalarm) ||
(~data & priv->lowalarm)) {
mask = POLLIN|POLLRDNORM;
}
DP(printk("gpio_poll ready: mask 0x%08X\n", mask));
return mask;
}
int etrax_gpio_wake_up_check(void)
{
struct gpio_private *priv = alarmlist;
unsigned long data = 0;
int ret = 0;
while (priv) {
data = *data_in[priv->minor];
if ((data & priv->highalarm) ||
(~data & priv->lowalarm)) {
DP(printk("etrax_gpio_wake_up_check %i\n",priv->minor));
wake_up_interruptible(&priv->alarm_wq);
ret = 1;
}
priv = priv->next;
}
return ret;
}
static irqreturn_t
gpio_poll_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
if (gpio_some_alarms) {
return IRQ_RETVAL(etrax_gpio_wake_up_check());
}
return IRQ_NONE;
}
static irqreturn_t
gpio_pa_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
reg_gio_rw_intr_mask intr_mask;
reg_gio_r_masked_intr masked_intr;
reg_gio_rw_ack_intr ack_intr;
unsigned long tmp;
unsigned long tmp2;
/* Find what PA interrupts are active */
masked_intr = REG_RD(gio, regi_gio, r_masked_intr);
tmp = REG_TYPE_CONV(unsigned long, reg_gio_r_masked_intr, masked_intr);
/* Find those that we have enabled */
spin_lock(&alarm_lock);
tmp &= (gpio_pa_high_alarms | gpio_pa_low_alarms);
spin_unlock(&alarm_lock);
/* Ack them */
ack_intr = REG_TYPE_CONV(reg_gio_rw_ack_intr, unsigned long, tmp);
REG_WR(gio, regi_gio, rw_ack_intr, ack_intr);
/* Disable those interrupts.. */
intr_mask = REG_RD(gio, regi_gio, rw_intr_mask);
tmp2 = REG_TYPE_CONV(unsigned long, reg_gio_rw_intr_mask, intr_mask);
tmp2 &= ~tmp;
intr_mask = REG_TYPE_CONV(reg_gio_rw_intr_mask, unsigned long, tmp2);
REG_WR(gio, regi_gio, rw_intr_mask, intr_mask);
if (gpio_some_alarms) {
return IRQ_RETVAL(etrax_gpio_wake_up_check());
}
return IRQ_NONE;
}
static ssize_t gpio_write(struct file * file, const char * buf, size_t count,
loff_t *off)
{
struct gpio_private *priv = (struct gpio_private *)file->private_data;
unsigned char data, clk_mask, data_mask, write_msb;
unsigned long flags;
unsigned long shadow;
volatile unsigned long *port;
ssize_t retval = count;
/* Only bits 0-7 may be used for write operations but allow all
devices except leds... */
if (priv->minor == GPIO_MINOR_LEDS) {
return -EFAULT;
}
if (!access_ok(VERIFY_READ, buf, count)) {
return -EFAULT;
}
clk_mask = priv->clk_mask;
data_mask = priv->data_mask;
/* It must have been configured using the IO_CFG_WRITE_MODE */
/* Perhaps a better error code? */
if (clk_mask == 0 || data_mask == 0) {
return -EPERM;
}
write_msb = priv->write_msb;
D(printk("gpio_write: %lu to data 0x%02X clk 0x%02X msb: %i\n",count, data_mask, clk_mask, write_msb));
port = data_out[priv->minor];
while (count--) {
int i;
data = *buf++;
if (priv->write_msb) {
for (i = 7; i >= 0;i--) {
local_irq_save(flags);
shadow = *port;
*port = shadow &= ~clk_mask;
if (data & 1<<i)
*port = shadow |= data_mask;
else
*port = shadow &= ~data_mask;
/* For FPGA: min 5.0ns (DCC) before CCLK high */
*port = shadow |= clk_mask;
local_irq_restore(flags);
}
} else {
for (i = 0; i <= 7;i++) {
local_irq_save(flags);
shadow = *port;
*port = shadow &= ~clk_mask;
if (data & 1<<i)
*port = shadow |= data_mask;
else
*port = shadow &= ~data_mask;
/* For FPGA: min 5.0ns (DCC) before CCLK high */
*port = shadow |= clk_mask;
local_irq_restore(flags);
}
}
}
return retval;
}
static int
gpio_open(struct inode *inode, struct file *filp)
{
struct gpio_private *priv;
int p = iminor(inode);
if (p > GPIO_MINOR_LAST)
return -EINVAL;
priv = (struct gpio_private *)kmalloc(sizeof(struct gpio_private),
GFP_KERNEL);
if (!priv)
return -ENOMEM;
priv->minor = p;
/* initialize the io/alarm struct and link it into our alarmlist */
priv->next = alarmlist;
alarmlist = priv;
priv->clk_mask = 0;
priv->data_mask = 0;
priv->highalarm = 0;
priv->lowalarm = 0;
init_waitqueue_head(&priv->alarm_wq);
filp->private_data = (void *)priv;
return 0;
}
static int
gpio_release(struct inode *inode, struct file *filp)
{
struct gpio_private *p = alarmlist;
struct gpio_private *todel = (struct gpio_private *)filp->private_data;
/* local copies while updating them: */
unsigned long a_high, a_low;
unsigned long some_alarms;
/* unlink from alarmlist and free the private structure */
if (p == todel) {
alarmlist = todel->next;
} else {
while (p->next != todel)
p = p->next;
p->next = todel->next;
}
kfree(todel);
/* Check if there are still any alarms set */
p = alarmlist;
some_alarms = 0;
a_high = 0;
a_low = 0;
while (p) {
if (p->minor == GPIO_MINOR_A) {
a_high |= p->highalarm;
a_low |= p->lowalarm;
}
if (p->highalarm | p->lowalarm) {
some_alarms = 1;
}
p = p->next;
}
spin_lock(&alarm_lock);
gpio_some_alarms = some_alarms;
gpio_pa_high_alarms = a_high;
gpio_pa_low_alarms = a_low;
spin_unlock(&alarm_lock);
return 0;
}
/* Main device API. ioctl's to read/set/clear bits, as well as to
* set alarms to wait for using a subsequent select().
*/
unsigned long inline setget_input(struct gpio_private *priv, unsigned long arg)
{
/* Set direction 0=unchanged 1=input,
* return mask with 1=input
*/
unsigned long flags;
unsigned long dir_shadow;
local_irq_save(flags);
dir_shadow = *dir_oe[priv->minor];
dir_shadow &= ~(arg & changeable_dir[priv->minor]);
*dir_oe[priv->minor] = dir_shadow;
local_irq_restore(flags);
if (priv->minor == GPIO_MINOR_A)
dir_shadow ^= 0xFF; /* Only 8 bits */
else
dir_shadow ^= 0x3FFFF; /* Only 18 bits */
return dir_shadow;
} /* setget_input */
unsigned long inline setget_output(struct gpio_private *priv, unsigned long arg)
{
unsigned long flags;
unsigned long dir_shadow;
local_irq_save(flags);
dir_shadow = *dir_oe[priv->minor];
dir_shadow |= (arg & changeable_dir[priv->minor]);
*dir_oe[priv->minor] = dir_shadow;
local_irq_restore(flags);
return dir_shadow;
} /* setget_output */
static int
gpio_leds_ioctl(unsigned int cmd, unsigned long arg);
static int
gpio_ioctl(struct inode *inode, struct file *file,
unsigned int cmd, unsigned long arg)
{
unsigned long flags;
unsigned long val;
unsigned long shadow;
struct gpio_private *priv = (struct gpio_private *)file->private_data;
if (_IOC_TYPE(cmd) != ETRAXGPIO_IOCTYPE) {
return -EINVAL;
}
switch (_IOC_NR(cmd)) {
case IO_READBITS: /* Use IO_READ_INBITS and IO_READ_OUTBITS instead */
// read the port
return *data_in[priv->minor];
break;
case IO_SETBITS:
local_irq_save(flags);
if (arg & 0x04)
printk("GPIO SET 2\n");
// set changeable bits with a 1 in arg
shadow = *data_out[priv->minor];
shadow |= (arg & changeable_bits[priv->minor]);
*data_out[priv->minor] = shadow;
local_irq_restore(flags);
break;
case IO_CLRBITS:
local_irq_save(flags);
if (arg & 0x04)
printk("GPIO CLR 2\n");
// clear changeable bits with a 1 in arg
shadow = *data_out[priv->minor];
shadow &= ~(arg & changeable_bits[priv->minor]);
*data_out[priv->minor] = shadow;
local_irq_restore(flags);
break;
case IO_HIGHALARM:
// set alarm when bits with 1 in arg go high
priv->highalarm |= arg;
spin_lock(&alarm_lock);
gpio_some_alarms = 1;
if (priv->minor == GPIO_MINOR_A) {
gpio_pa_high_alarms |= arg;
}
spin_unlock(&alarm_lock);
break;
case IO_LOWALARM:
// set alarm when bits with 1 in arg go low
priv->lowalarm |= arg;
spin_lock(&alarm_lock);
gpio_some_alarms = 1;
if (priv->minor == GPIO_MINOR_A) {
gpio_pa_low_alarms |= arg;
}
spin_unlock(&alarm_lock);
break;
case IO_CLRALARM:
// clear alarm for bits with 1 in arg
priv->highalarm &= ~arg;
priv->lowalarm &= ~arg;
spin_lock(&alarm_lock);
if (priv->minor == GPIO_MINOR_A) {
if (gpio_pa_high_alarms & arg ||
gpio_pa_low_alarms & arg) {
/* Must update the gpio_pa_*alarms masks */
}
}
spin_unlock(&alarm_lock);
break;
case IO_READDIR: /* Use IO_SETGET_INPUT/OUTPUT instead! */
/* Read direction 0=input 1=output */
return *dir_oe[priv->minor];
case IO_SETINPUT: /* Use IO_SETGET_INPUT instead! */
/* Set direction 0=unchanged 1=input,
* return mask with 1=input
*/
return setget_input(priv, arg);
break;
case IO_SETOUTPUT: /* Use IO_SETGET_OUTPUT instead! */
/* Set direction 0=unchanged 1=output,
* return mask with 1=output
*/
return setget_output(priv, arg);
case IO_CFG_WRITE_MODE:
{
unsigned long dir_shadow;
dir_shadow = *dir_oe[priv->minor];
priv->clk_mask = arg & 0xFF;
priv->data_mask = (arg >> 8) & 0xFF;
priv->write_msb = (arg >> 16) & 0x01;
/* Check if we're allowed to change the bits and
* the direction is correct
*/
if (!((priv->clk_mask & changeable_bits[priv->minor]) &&
(priv->data_mask & changeable_bits[priv->minor]) &&
(priv->clk_mask & dir_shadow) &&
(priv->data_mask & dir_shadow)))
{
priv->clk_mask = 0;
priv->data_mask = 0;
return -EPERM;
}
break;
}
case IO_READ_INBITS:
/* *arg is result of reading the input pins */
val = *data_in[priv->minor];
if (copy_to_user((unsigned long*)arg, &val, sizeof(val)))
return -EFAULT;
return 0;
break;
case IO_READ_OUTBITS:
/* *arg is result of reading the output shadow */
val = *data_out[priv->minor];
if (copy_to_user((unsigned long*)arg, &val, sizeof(val)))
return -EFAULT;
break;
case IO_SETGET_INPUT:
/* bits set in *arg is set to input,
* *arg updated with current input pins.
*/
if (copy_from_user(&val, (unsigned long*)arg, sizeof(val)))
return -EFAULT;
val = setget_input(priv, val);
if (copy_to_user((unsigned long*)arg, &val, sizeof(val)))
return -EFAULT;
break;
case IO_SETGET_OUTPUT:
/* bits set in *arg is set to output,
* *arg updated with current output pins.
*/
if (copy_from_user(&val, (unsigned long*)arg, sizeof(val)))
return -EFAULT;
val = setget_output(priv, val);
if (copy_to_user((unsigned long*)arg, &val, sizeof(val)))
return -EFAULT;
break;
default:
if (priv->minor == GPIO_MINOR_LEDS)
return gpio_leds_ioctl(cmd, arg);
else
return -EINVAL;
} /* switch */
return 0;
}
static int
gpio_leds_ioctl(unsigned int cmd, unsigned long arg)
{
unsigned char green;
unsigned char red;
switch (_IOC_NR(cmd)) {
case IO_LEDACTIVE_SET:
green = ((unsigned char) arg) & 1;
red = (((unsigned char) arg) >> 1) & 1;
LED_ACTIVE_SET_G(green);
LED_ACTIVE_SET_R(red);
break;
default:
return -EINVAL;
} /* switch */
return 0;
}
struct file_operations gpio_fops = {
.owner = THIS_MODULE,
.poll = gpio_poll,
.ioctl = gpio_ioctl,
.write = gpio_write,
.open = gpio_open,
.release = gpio_release,
};
/* main driver initialization routine, called from mem.c */
static __init int
gpio_init(void)
{
int res;
reg_intr_vect_rw_mask intr_mask;
/* do the formalities */
res = register_chrdev(GPIO_MAJOR, gpio_name, &gpio_fops);
if (res < 0) {
printk(KERN_ERR "gpio: couldn't get a major number.\n");
return res;
}
/* Clear all leds */
LED_NETWORK_SET(0);
LED_ACTIVE_SET(0);
LED_DISK_READ(0);
LED_DISK_WRITE(0);
printk("ETRAX FS GPIO driver v2.5, (c) 2003-2005 Axis Communications AB\n");
/* We call etrax_gpio_wake_up_check() from timer interrupt and
* from cpu_idle() in kernel/process.c
* The check in cpu_idle() reduces latency from ~15 ms to ~6 ms
* in some tests.
*/
if (request_irq(TIMER_INTR_VECT, gpio_poll_timer_interrupt,
IRQF_SHARED | IRQF_DISABLED,"gpio poll", &alarmlist)) {
printk("err: timer0 irq for gpio\n");
}
if (request_irq(GEN_IO_INTR_VECT, gpio_pa_interrupt,
IRQF_SHARED | IRQF_DISABLED,"gpio PA", &alarmlist)) {
printk("err: PA irq for gpio\n");
}
/* enable the gio and timer irq in global config */
intr_mask = REG_RD(intr_vect, regi_irq, rw_mask);
intr_mask.timer = 1;
intr_mask.gen_io = 1;
REG_WR(intr_vect, regi_irq, rw_mask, intr_mask);
return res;
}
/* this makes sure that gpio_init is called during kernel boot */
module_init(gpio_init);