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