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Re: [PATCH][MIPS][3/7] AR7: gpio char device

To: technoboy85@gmail.com, David Brownell <david-b@pacbell.net>
Subject: Re: [PATCH][MIPS][3/7] AR7: gpio char device
From: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Date: Sun, 23 Sep 2007 01:42:01 +0900 (JST)
Cc: linux-mips@linux-mips.org, nico@openwrt.org, akpm@linux-foundation.org
In-reply-to: <200709201800.53887.technoboy85@gmail.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <200709201728.10866.technoboy85@gmail.com> <200709201800.53887.technoboy85@gmail.com>
Sender: linux-mips-bounce@linux-mips.org
On Thu, 20 Sep 2007 18:00:53 +0200, Matteo Croce <technoboy85@gmail.com> wrote:
> Char device to access GPIO pins
> 
> Signed-off-by: Matteo Croce <technoboy85@gmail.com>
> Signed-off-by: Nicolas Thill <nico@openwrt.org>

This driver is almost platform independent.  The only
platform-specific part is its name and AR7_GPIO_MAX.  It would be
great if this driver was really "generic" and could be used with any
GPIO API providers.

I think there were some discussions about userspace API for GPIO on
LKML, but cannot remember the detail.

David, give us a comment please?

> diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
> index b391776..b98aedf 100644
> --- a/drivers/char/Kconfig
> +++ b/drivers/char/Kconfig
> @@ -928,6 +928,15 @@ config MWAVE
>         To compile this driver as a module, choose M here: the
>         module will be called mwave.
>  
> +config AR7_GPIO
> +     tristate "TI AR7 GPIO Support"
> +     depends on AR7
> +     help
> +       Give userspace access to the GPIO pins on the Texas Instruments AR7 
> +       processors.
> +
> +       If compiled as a module, it will be called ar7_gpio.
> +
>  config SCx200_GPIO
>       tristate "NatSemi SCx200 GPIO Support"
>       depends on SCx200
> diff --git a/drivers/char/Makefile b/drivers/char/Makefile
> index d68ddbe..804319e 100644
> --- a/drivers/char/Makefile
> +++ b/drivers/char/Makefile
> @@ -89,6 +89,7 @@ obj-$(CONFIG_COBALT_LCD)    += lcd.o
>  obj-$(CONFIG_PPDEV)          += ppdev.o
>  obj-$(CONFIG_NWBUTTON)               += nwbutton.o
>  obj-$(CONFIG_NWFLASH)                += nwflash.o
> +obj-$(CONFIG_AR7_GPIO)               += ar7_gpio.o
>  obj-$(CONFIG_SCx200_GPIO)    += scx200_gpio.o
>  obj-$(CONFIG_PC8736x_GPIO)   += pc8736x_gpio.o
>  obj-$(CONFIG_NSC_GPIO)               += nsc_gpio.o
> diff --git a/drivers/char/ar7_gpio.c b/drivers/char/ar7_gpio.c
> new file mode 100644
> index 0000000..d57a23e
> --- /dev/null
> +++ b/drivers/char/ar7_gpio.c
> @@ -0,0 +1,158 @@
> +/*
> + * Copyright (C) 2007 Nicolas Thill <nico@openwrt.org>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
> + */
> +
> +#include <linux/device.h>
> +#include <linux/fs.h>
> +#include <linux/module.h>
> +#include <linux/errno.h>
> +#include <linux/kernel.h>
> +#include <linux/init.h>
> +#include <linux/platform_device.h>
> +#include <linux/uaccess.h>
> +#include <linux/io.h>
> +#include <linux/types.h>
> +#include <linux/cdev.h>
> +#include <gpio.h>

This should be "#include <asm/gpio.h>".

> +
> +#define DRVNAME "ar7_gpio"
> +#define LONGNAME "TI AR7 GPIOs Driver"
> +
> +MODULE_AUTHOR("Nicolas Thill <nico@openwrt.org>");
> +MODULE_DESCRIPTION(LONGNAME);
> +MODULE_LICENSE("GPL");
> +
> +static int ar7_gpio_major;
> +
> +static ssize_t ar7_gpio_write(struct file *file, const char __user *buf,
> +     size_t len, loff_t *ppos)
> +{
> +     int pin = iminor(file->f_dentry->d_inode);
> +     size_t i;
> +
> +     for (i = 0; i < len; ++i) {
> +             char c;
> +             if (get_user(c, buf + i))
> +                     return -EFAULT;
> +             switch (c) {
> +             case '0':
> +                     gpio_set_value(pin, 0);
> +                     break;
> +             case '1':
> +                     gpio_set_value(pin, 1);
> +                     break;
> +             case 'd':
> +             case 'D':
> +                     ar7_gpio_disable(pin);
> +                     break;
> +             case 'e':
> +             case 'E':
> +                     ar7_gpio_enable(pin);
> +                     break;
> +             case 'i':
> +             case 'I':
> +             case '<':
> +                     gpio_direction_input(pin);
> +                     break;
> +             case 'o':
> +             case 'O':
> +             case '>':
> +                     gpio_direction_output(pin);
> +                     break;
> +             default:
> +                     return -EINVAL;
> +             }
> +     }
> +
> +     return len;
> +}
> +
> +static ssize_t ar7_gpio_read(struct file *file, char __user *buf,
> +     size_t len, loff_t *ppos)
> +{
> +     int pin = iminor(file->f_dentry->d_inode);
> +     int value;
> +
> +     value = gpio_get_value(pin);
> +     if (put_user(value ? '1' : '0', buf))
> +             return -EFAULT;
> +
> +     return 1;
> +}
> +
> +static int ar7_gpio_open(struct inode *inode, struct file *file)
> +{
> +     int m = iminor(inode);
> +
> +     if (m >= AR7_GPIO_MAX)
> +             return -EINVAL;
> +
> +     return nonseekable_open(inode, file);
> +}
> +
> +static int ar7_gpio_release(struct inode *inode, struct file *file)
> +{
> +     return 0;
> +}
> +
> +static const struct file_operations ar7_gpio_fops = {
> +     .owner   = THIS_MODULE,
> +     .write   = ar7_gpio_write,
> +     .read    = ar7_gpio_read,
> +     .open    = ar7_gpio_open,
> +     .release = ar7_gpio_release,
> +     .llseek  = no_llseek,
> +};
> +
> +static struct platform_device *ar7_gpio_device;
> +
> +static int __init ar7_gpio_init(void)
> +{
> +     int rc;
> +
> +     ar7_gpio_device = platform_device_alloc(DRVNAME, -1);
> +     if (!ar7_gpio_device)
> +             return -ENOMEM;
> +
> +     rc = platform_device_add(ar7_gpio_device);
> +     if (rc < 0)
> +             goto out_put;
> +
> +     rc = register_chrdev(ar7_gpio_major, DRVNAME, &ar7_gpio_fops);
> +     if (rc < 0)
> +             goto out_put;
> +
> +     ar7_gpio_major = rc;
> +
> +     rc = 0;
> +
> +     goto out;
> +
> +out_put:
> +     platform_device_put(ar7_gpio_device);
> +out:
> +     return rc;
> +}
> +
> +static void __exit ar7_gpio_exit(void)
> +{
> +     unregister_chrdev(ar7_gpio_major, DRVNAME);
> +     platform_device_unregister(ar7_gpio_device);
> +}
> +
> +module_init(ar7_gpio_init);
> +module_exit(ar7_gpio_exit);

---
Atsushi Nemoto

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