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 * FIXME: Has anyone spotted any locking functions int his code recently ?? 52 */ 53 54 int button_add_callback (void (*callback) (void), int count) 55 { 56 int lp = 0; 57 if (callback_count == 32) { 58 return -ENOMEM; 59 } 60 if (!callback) { 61 return -EINVAL; 62 } 63 callback_count++; 64 for (; (button_callback_list [lp].callback); lp++); 65 button_callback_list [lp].callback = callback; 66 button_callback_list [lp].count = count; 67 return 0; 68 } 69 70 /* 71 * This function is called by other drivers to deregister a callback function. 72 * If you attempt to unregister a callback which does not exist, it will fail 73 * with -EINVAL. If there is more than one entry with the same address, 74 * because it searches the list from end to beginning, it will unregister the 75 * last one to be registered first (FILO- First In Last Out). 76 * Note that this is not neccessarily true if the entries are not submitted 77 * at the same time, because another driver could have unregistered a callback 78 * between the submissions creating a gap earlier in the list, which would 79 * be filled first at submission time. 80 */ 81 82 int button_del_callback (void (*callback) (void)) 83 { 84 int lp = 31; 85 if (!callback) { 86 return -EINVAL; 87 } 88 while (lp >= 0) { 89 if ((button_callback_list [lp].callback) == callback) { 90 button_callback_list [lp].callback = NULL; 91 button_callback_list [lp].count = 0; 92 callback_count--; 93 return 0; 94 }; 95 lp--; 96 }; 97 return -EINVAL; 98 } 99 100 /* 101 * This function is called by button_sequence_finished to search through the 102 * list of callback functions, and call any of them whose count argument 103 * matches the current count of button presses. It starts at the beginning 104 * of the list and works up to the end. It will refuse to follow a null 105 * pointer (which should never happen anyway). 106 */ 107 108 static void button_consume_callbacks (int bpcount) 109 { 110 int lp = 0; 111 for (; lp <= 31; lp++) { 112 if ((button_callback_list [lp].count) == bpcount) { 113 if (button_callback_list [lp].callback) { 114 button_callback_list[lp].callback(); 115 } 116 } 117 } 118 } 119 120 /* 121 * This function is called when the button_timer times out. 122 * ie. When you don't press the button for bdelay jiffies, this is taken to 123 * mean you have ended the sequence of key presses, and this function is 124 * called to wind things up (write the press_count out to /dev/button, call 125 * any matching registered function callbacks, initiate reboot, etc.). 126 */ 127 128 static void button_sequence_finished (unsigned long parameters) 129 { 130 #ifdef CONFIG_NWBUTTON_REBOOT /* Reboot using button is enabled */ 131 if (button_press_count == reboot_count) { 132 kill_proc (1, SIGINT, 1); /* Ask init to reboot us */ 133 } 134 #endif /* CONFIG_NWBUTTON_REBOOT */ 135 button_consume_callbacks (button_press_count); 136 bcount = sprintf (button_output_buffer, "%d\n", button_press_count); 137 button_press_count = 0; /* Reset the button press counter */ 138 wake_up_interruptible (&button_wait_queue); 139 } 140 141 /* 142 * This handler is called when the orange button is pressed (GPIO 10 of the 143 * SuperIO chip, which maps to logical IRQ 26). If the press_count is 0, 144 * this is the first press, so it starts a timer and increments the counter. 145 * If it is higher than 0, it deletes the old timer, starts a new one, and 146 * increments the counter. 147 */ 148 149 static irqreturn_t button_handler (int irq, void *dev_id, struct pt_regs *regs) 150 { 151 if (button_press_count) { 152 del_timer (&button_timer); 153 } 154 button_press_count++; 155 init_timer (&button_timer); 156 button_timer.function = button_sequence_finished; 157 button_timer.expires = (jiffies + bdelay); 158 add_timer (&button_timer); 159 160 return IRQ_HANDLED; 161 } 162 163 /* 164 * This function is called when a user space program attempts to read 165 * /dev/nwbutton. It puts the device to sleep on the wait queue until 166 * button_sequence_finished writes some data to the buffer and flushes 167 * the queue, at which point it writes the data out to the device and 168 * returns the number of characters it has written. This function is 169 * reentrant, so that many processes can be attempting to read from the 170 * device at any one time. 171 */ 172 173 static int button_read (struct file *filp, char __user *buffer, 174 size_t count, loff_t *ppos) 175 { 176 interruptible_sleep_on (&button_wait_queue); 177 return (copy_to_user (buffer, &button_output_buffer, bcount)) 178 ? -EFAULT : bcount; 179 } 180 181 /* 182 * This structure is the file operations structure, which specifies what 183 * callbacks functions the kernel should call when a user mode process 184 * attempts to perform these operations on the device. 185 */ 186 187 static struct file_operations button_fops = { 188 .owner = THIS_MODULE, 189 .read = button_read, 190 }; 191 192 /* 193 * This structure is the misc device structure, which specifies the minor 194 * device number (158 in this case), the name of the device (for /proc/misc), 195 * and the address of the above file operations structure. 196 */ 197 198 static struct miscdevice button_misc_device = { 199 BUTTON_MINOR, 200 "nwbutton", 201 &button_fops, 202 }; 203 204 /* 205 * This function is called to initialise the driver, either from misc.c at 206 * bootup if the driver is compiled into the kernel, or from init_module 207 * below at module insert time. It attempts to register the device node 208 * and the IRQ and fails with a warning message if either fails, though 209 * neither ever should because the device number and IRQ are unique to 210 * this driver. 211 */ 212 213 static int __init nwbutton_init(void) 214 { 215 if (!machine_is_netwinder()) 216 return -ENODEV; 217 218 printk (KERN_INFO "NetWinder Button Driver Version %s (C) Alex Holden " 219 "<alex@linuxhacker.org> 1998.\n", VERSION); 220 221 if (misc_register (&button_misc_device)) { 222 printk (KERN_WARNING "nwbutton: Couldn't register device 10, " 223 "%d.\n", BUTTON_MINOR); 224 return -EBUSY; 225 } 226 227 if (request_irq (IRQ_NETWINDER_BUTTON, button_handler, SA_INTERRUPT, 228 "nwbutton", NULL)) { 229 printk (KERN_WARNING "nwbutton: IRQ %d is not free.\n", 230 IRQ_NETWINDER_BUTTON); 231 misc_deregister (&button_misc_device); 232 return -EIO; 233 } 234 return 0; 235 } 236 237 static void __exit nwbutton_exit (void) 238 { 239 free_irq (IRQ_NETWINDER_BUTTON, NULL); 240 misc_deregister (&button_misc_device); 241 } 242 243 244 MODULE_AUTHOR("Alex Holden"); 245 MODULE_LICENSE("GPL"); 246 247 module_init(nwbutton_init); 248 module_exit(nwbutton_exit); 249