blob: 76c490fa051103b99ba6b1006f7b8c2ed2a575a2 [file] [log] [blame]
* NetWinder Button Driver-
* Copyright (C) Alex Holden <> 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;
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 necessarily 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;
return 0;
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) {
* 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 */
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)
mod_timer(&button_timer, jiffies + bdelay);
* 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)
prepare_to_wait(&button_wait_queue, &wait, TASK_INTERRUPTIBLE);
finish_wait(&button_wait_queue, &wait);
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,
.llseek = noop_llseek,
* 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 = {
* 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 "
"<> 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, 0,
"nwbutton", NULL)) {
printk (KERN_WARNING "nwbutton: IRQ %d is not free.\n",
misc_deregister (&button_misc_device);
return -EIO;
return 0;
static void __exit nwbutton_exit (void)
misc_deregister (&button_misc_device);
MODULE_AUTHOR("Alex Holden");