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/*

 *      NetWinder Button Driver-

 *      Copyright (C) Alex Holden <alex@linuxhacker.org> 1998, 1999.

 *

 */

#include <linux/module.h>

#include <linux/kernel.h>

#include <linux/sched.h>

#include <linux/interrupt.h>

#include <linux/time.h>

#include <linux/timer.h>

#include <linux/fs.h>

#include <linux/miscdevice.h>

#include <linux/string.h>

#include <linux/errno.h>

#include <linux/init.h>

#include <asm/uaccess.h>

#include <asm/irq.h>

#include <asm/mach-types.h>

#define __NWBUTTON_C            /* Tell the header file who we are */

#include "nwbutton.h"

static void button_sequence_finished (unsigned long parameters);

static int button_press_count;          /* The count of button presses */

/* Times for the end of a sequence */

static DEFINE_TIMER(button_timer, button_sequence_finished, 0, 0);

static DECLARE_WAIT_QUEUE_HEAD(button_wait_queue); /* Used for blocking read */

static char button_output_buffer[32];   /* Stores data to write out of device */

static int bcount;                      /* The number of bytes in the buffer */

static int bdelay = BUTTON_DELAY;       /* The delay, in jiffies */

static struct button_callback button_callback_list[32]; /* The callback list */

static int callback_count;              /* The number of callbacks registered */

static int reboot_count = NUM_PRESSES_REBOOT; /* Number of presses to reboot */

/*

 * This function is called by other drivers to register a callback function

 * to be called when a particular number of button presses occurs.

 * The callback list is a static array of 32 entries (I somehow doubt many

 * people are ever going to want to register more than 32 different actions

 * to be performed by the kernel on different numbers of button presses ;).

 * However, if an attempt to register a 33rd entry (perhaps a stuck loop

 * somewhere registering the same entry over and over?) it will fail to

 * do so and return -ENOMEM. If an attempt is made to register a null pointer,

 * it will fail to do so and return -EINVAL.

 * Because callbacks can be unregistered at random the list can become

 * fragmented, so we need to search through the list until we find the first

 * free entry.

 *

 * FIXME: Has anyone spotted any locking functions int his code recently ??

 */

int button_add_callback (void (*callback) (void), int count)

{

        int lp = 0;

        if (callback_count == 32) {

                return -ENOMEM;

        }

        if (!callback) {

                return -EINVAL;

        }

        callback_count++;

        for (; (button_callback_list [lp].callback); lp++);

        button_callback_list [lp].callback = callback;

        button_callback_list [lp].count = count;

        return 0;

}

/*

 * This function is called by other drivers to deregister a callback function.

 * If you attempt to unregister a callback which does not exist, it will fail

 * with -EINVAL. If there is more than one entry with the same address,

 * because it searches the list from end to beginning, it will unregister the

 * last one to be registered first (FILO- First In Last Out).

 * Note that this is not neccessarily true if the entries are not submitted

 * at the same time, because another driver could have unregistered a callback

 * between the submissions creating a gap earlier in the list, which would

 * be filled first at submission time.

 */

int button_del_callback (void (*callback) (void))

{

        int lp = 31;

        if (!callback) {

                return -EINVAL;

        }

        while (lp >= 0) {

                if ((button_callback_list [lp].callback) == callback) {

                        button_callback_list [lp].callback = NULL;

                        button_callback_list [lp].count = 0;

                        callback_count--;

                        return 0;

                };

                lp--;

        };

        return -EINVAL;

}

/*

 * This function is called by button_sequence_finished to search through the

 * list of callback functions, and call any of them whose count argument

 * matches the current count of button presses. It starts at the beginning

 * of the list and works up to the end. It will refuse to follow a null

 * pointer (which should never happen anyway).

 */

static void button_consume_callbacks (int bpcount)

{

        int lp = 0;

        for (; lp <= 31; lp++) {

                if ((button_callback_list [lp].count) == bpcount) {

                        if (button_callback_list [lp].callback) {

                                button_callback_list[lp].callback();

                        }

                }

        }

}

/*

 * This function is called when the button_timer times out.

 * ie. When you don't press the button for bdelay jiffies, this is taken to

 * mean you have ended the sequence of key presses, and this function is

 * called to wind things up (write the press_count out to /dev/button, call

 * any matching registered function callbacks, initiate reboot, etc.).

 */

static void button_sequence_finished (unsigned long parameters)

{

#ifdef CONFIG_NWBUTTON_REBOOT           /* Reboot using button is enabled */

        if (button_press_count == reboot_count)

                kill_cad_pid(SIGINT, 1);        /* Ask init to reboot us */

#endif /* CONFIG_NWBUTTON_REBOOT */

        button_consume_callbacks (button_press_count);

        bcount = sprintf (button_output_buffer, "%d\n", button_press_count);

        button_press_count = 0;          /* Reset the button press counter */

        wake_up_interruptible (&button_wait_queue);

}

/*

 *  This handler is called when the orange button is pressed (GPIO 10 of the

 *  SuperIO chip, which maps to logical IRQ 26). If the press_count is 0,

 *  this is the first press, so it starts a timer and increments the counter.

 *  If it is higher than 0, it deletes the old timer, starts a new one, and

 *  increments the counter.

 */

static irqreturn_t button_handler (int irq, void *dev_id)

{

        button_press_count++;

        mod_timer(&button_timer, jiffies + bdelay);

        return IRQ_HANDLED;

}

/*

 * This function is called when a user space program attempts to read

 * /dev/nwbutton. It puts the device to sleep on the wait queue until

 * button_sequence_finished writes some data to the buffer and flushes

 * the queue, at which point it writes the data out to the device and

 * returns the number of characters it has written. This function is

 * reentrant, so that many processes can be attempting to read from the

 * device at any one time.

 */

static int button_read (struct file *filp, char __user *buffer,

                        size_t count, loff_t *ppos)

{

        interruptible_sleep_on (&button_wait_queue);

        return (copy_to_user (buffer, &button_output_buffer, bcount))

                 ? -EFAULT : bcount;

}

/*

 * This structure is the file operations structure, which specifies what

 * callbacks functions the kernel should call when a user mode process

 * attempts to perform these operations on the device.

 */

static const struct file_operations button_fops = {

        .owner          = THIS_MODULE,

        .read           = button_read,

};

/*

 * This structure is the misc device structure, which specifies the minor

 * device number (158 in this case), the name of the device (for /proc/misc),

 * and the address of the above file operations structure.

 */

static struct miscdevice button_misc_device = {

        BUTTON_MINOR,

        "nwbutton",

        &button_fops,

};

/*

 * This function is called to initialise the driver, either from misc.c at

 * bootup if the driver is compiled into the kernel, or from init_module

 * below at module insert time. It attempts to register the device node

 * and the IRQ and fails with a warning message if either fails, though

 * neither ever should because the device number and IRQ are unique to

 * this driver.

 */

static int __init nwbutton_init(void)

{

        if (!machine_is_netwinder())

                return -ENODEV;

        printk (KERN_INFO "NetWinder Button Driver Version %s (C) Alex Holden "

                        "<alex@linuxhacker.org> 1998.\n", VERSION);

        if (misc_register (&button_misc_device)) {

                printk (KERN_WARNING "nwbutton: Couldn't register device 10, "

                                "%d.\n", BUTTON_MINOR);

                return -EBUSY;

        }

        if (request_irq (IRQ_NETWINDER_BUTTON, button_handler, IRQF_DISABLED,

                        "nwbutton", NULL)) {

                printk (KERN_WARNING "nwbutton: IRQ %d is not free.\n",

                                IRQ_NETWINDER_BUTTON);

                misc_deregister (&button_misc_device);

                return -EIO;

        }

        return 0;

}

static void __exit nwbutton_exit (void)

{

        free_irq (IRQ_NETWINDER_BUTTON, NULL);

        misc_deregister (&button_misc_device);

}

MODULE_AUTHOR("Alex Holden");

MODULE_LICENSE("GPL");

module_init(nwbutton_init);

module_exit(nwbutton_exit);