drivers/char/nwbutton.c

   1 /*
   2  *      NetWinder Button Driver-
   3  *      Copyright (C) Alex Holden <alex@linuxhacker.org> 1998, 1999.
   4  *
   5  */
   6
   7 #include <linux/config.h>
   8 #include <linux/module.h>
   9 #include <linux/kernel.h>
  10 #include <linux/sched.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/time.h>
  13 #include <linux/timer.h>
  14 #include <linux/fs.h>
  15 #include <linux/miscdevice.h>
  16 #include <linux/string.h>
  17 #include <linux/errno.h>
  18 #include <linux/init.h>
  19
  20 #include <asm/uaccess.h>
  21 #include <asm/irq.h>
  22 #define __NWBUTTON_C            /* Tell the header file who we are */
  23 #include "nwbutton.h"
  24
  25 static int button_press_count;          /* The count of button presses */
  26 static struct timer_list button_timer;  /* Times for the end of a sequence */
  27 static DECLARE_WAIT_QUEUE_HEAD(button_wait_queue); /* Used for blocking read */
  28 static char button_output_buffer[32];   /* Stores data to write out of device */
  29 static int bcount;                      /* The number of bytes in the buffer */
  30 static int bdelay = BUTTON_DELAY;       /* The delay, in jiffies */
  31 static struct button_callback button_callback_list[32]; /* The callback list */
  32 static int callback_count;              /* The number of callbacks registered */
  33 static int reboot_count = NUM_PRESSES_REBOOT; /* Number of presses to reboot */
  34
  35 /*
  36  * This function is called by other drivers to register a callback function
  37  * to be called when a particular number of button presses occurs.
  38  * The callback list is a static array of 32 entries (I somehow doubt many
  39  * people are ever going to want to register more than 32 different actions
  40  * to be performed by the kernel on different numbers of button presses ;).
  41  * However, if an attempt to register a 33rd entry (perhaps a stuck loop
  42  * somewhere registering the same entry over and over?) it will fail to
  43  * do so and return -ENOMEM. If an attempt is made to register a null pointer,
  44  * it will fail to do so and return -EINVAL.
  45  * Because callbacks can be unregistered at random the list can become
  46  * fragmented, so we need to search through the list until we find the first
  47  * free entry.
  48  */
  49
  50 int button_add_callback (void (*callback) (void), int count)
  51 {
  52         int lp = 0;
  53         if (callback_count == 32) {
  54                 return -ENOMEM;
  55         }
  56         if (!callback) {
  57                 return -EINVAL;
  58         }
  59         callback_count++;
  60         for (; (button_callback_list [lp].callback); lp++);
  61         button_callback_list [lp].callback = callback;
  62         button_callback_list [lp].count = count;
  63         return 0;
  64 }
  65
  66 /*
  67  * This function is called by other drivers to deregister a callback function.
  68  * If you attempt to unregister a callback which does not exist, it will fail
  69  * with -EINVAL. If there is more than one entry with the same address,
  70  * because it searches the list from end to beginning, it will unregister the
  71  * last one to be registered first (FILO- First In Last Out).
  72  * Note that this is not neccessarily true if the entries are not submitted
  73  * at the same time, because another driver could have unregistered a callback
  74  * between the submissions creating a gap earlier in the list, which would
  75  * be filled first at submission time.
  76  */
  77
  78 int button_del_callback (void (*callback) (void))
  79 {
  80         int lp = 31;
  81         if (!callback) {
  82                 return -EINVAL;
  83         }
  84         while (lp >= 0) {
  85                 if ((button_callback_list [lp].callback) == callback) {
  86                         button_callback_list [lp].callback = NULL;
  87                         button_callback_list [lp].count = 0;
  88                         callback_count--;
  89                         return 0;
  90                 };
  91                 lp--;
  92         };
  93         return -EINVAL;
  94 }
  95
  96 /*
  97  * This function is called by button_sequence_finished to search through the
  98  * list of callback functions, and call any of them whose count argument
  99  * matches the current count of button presses. It starts at the beginning
 100  * of the list and works up to the end. It will refuse to follow a null
 101  * pointer (which should never happen anyway).
 102  */
 103
 104 static void button_consume_callbacks (int bpcount)
 105 {
 106         int lp = 0;
 107         for (; lp <= 31; lp++) {
 108                 if ((button_callback_list [lp].count) == bpcount) {
 109                         if (button_callback_list [lp].callback) {
 110                                 button_callback_list[lp].callback();
 111                         }
 112                 }
 113         }
 114 }
 115
 116 /*
 117  * This function is called when the button_timer times out.
 118  * ie. When you don't press the button for bdelay jiffies, this is taken to
 119  * mean you have ended the sequence of key presses, and this function is
 120  * called to wind things up (write the press_count out to /dev/button, call
 121  * any matching registered function callbacks, initiate reboot, etc.).
 122  */
 123
 124 static void button_sequence_finished (unsigned long parameters)
 125 {
 126 #ifdef CONFIG_NWBUTTON_REBOOT           /* Reboot using button is enabled */
 127         if (button_press_count == reboot_count) {
 128                 kill_proc (1, SIGINT, 1);       /* Ask init to reboot us */
 129         }
 130 #endif /* CONFIG_NWBUTTON_REBOOT */
 131         button_consume_callbacks (button_press_count);
 132         bcount = sprintf (button_output_buffer, "%d\n", button_press_count);
 133         button_press_count = 0;         /* Reset the button press counter */
 134         wake_up_interruptible (&button_wait_queue);
 135 }
 136
 137 /*
 138  *  This handler is called when the orange button is pressed (GPIO 10 of the
 139  *  SuperIO chip, which maps to logical IRQ 26). If the press_count is 0,
 140  *  this is the first press, so it starts a timer and increments the counter.
 141  *  If it is higher than 0, it deletes the old timer, starts a new one, and
 142  *  increments the counter.
 143  */
 144
 145 static void button_handler (int irq, void *dev_id, struct pt_regs *regs)
 146 {
 147         if (button_press_count) {
 148                 del_timer (&button_timer);
 149         }
 150         button_press_count++;
 151         init_timer (&button_timer);
 152         button_timer.function = button_sequence_finished;
 153         button_timer.expires = (jiffies + bdelay);
 154         add_timer (&button_timer);
 155 }
 156
 157 /*
 158  * This function is called when a user space program attempts to read
 159  * /dev/nwbutton. It puts the device to sleep on the wait queue until
 160  * button_sequence_finished writes some data to the buffer and flushes
 161  * the queue, at which point it writes the data out to the device and
 162  * returns the number of characters it has written. This function is
 163  * reentrant, so that many processes can be attempting to read from the
 164  * device at any one time.
 165  */
 166
 167 static int button_read (struct file *filp, char *buffer,
 168                         size_t count, loff_t *ppos)
 169 {
 170         interruptible_sleep_on (&button_wait_queue);
 171         return (copy_to_user (buffer, &button_output_buffer, bcount))
 172                  ? -EFAULT : bcount;
 173 }
 174
 175 /*
 176  * This structure is the file operations structure, which specifies what
 177  * callbacks functions the kernel should call when a user mode process
 178  * attempts to perform these operations on the device.
 179  */
 180
 181 static struct file_operations button_fops = {
 182         owner:          THIS_MODULE,
 183         read:           button_read,
 184 };
 185
 186 /*
 187  * This structure is the misc device structure, which specifies the minor
 188  * device number (158 in this case), the name of the device (for /proc/misc),
 189  * and the address of the above file operations structure.
 190  */
 191
 192 static struct miscdevice button_misc_device = {
 193         BUTTON_MINOR,
 194         "nwbutton",
 195         &button_fops,
 196 };
 197
 198 /*
 199  * This function is called to initialise the driver, either from misc.c at
 200  * bootup if the driver is compiled into the kernel, or from init_module
 201  * below at module insert time. It attempts to register the device node
 202  * and the IRQ and fails with a warning message if either fails, though
 203  * neither ever should because the device number and IRQ are unique to
 204  * this driver.
 205  */
 206
 207 static int __init nwbutton_init(void)
 208 {
 209         if (!machine_is_netwinder())
 210                 return -ENODEV;
 211
 212         printk (KERN_INFO "NetWinder Button Driver Version %s (C) Alex Holden "
 213                         "<alex@linuxhacker.org> 1998.\n", VERSION);
 214
 215         if (misc_register (&button_misc_device)) {
 216                 printk (KERN_WARNING "nwbutton: Couldn't register device 10, "
 217                                 "%d.\n", BUTTON_MINOR);
 218                 return -EBUSY;
 219         }
 220
 221         if (request_irq (IRQ_NETWINDER_BUTTON, button_handler, SA_INTERRUPT,
 222                         "nwbutton", NULL)) {
 223                 printk (KERN_WARNING "nwbutton: IRQ %d is not free.\n",
 224                                 IRQ_NETWINDER_BUTTON);
 225                 misc_deregister (&button_misc_device);
 226                 return -EIO;
 227         }
 228         return 0;
 229 }
 230
 231 static void __exit nwbutton_exit (void)
 232 {
 233         free_irq (IRQ_NETWINDER_BUTTON, NULL);
 234         misc_deregister (&button_misc_device);
 235 }
 236
 237 EXPORT_NO_SYMBOLS;
 238
 239 module_init(nwbutton_init);
 240 module_exit(nwbutton_exit);