1 /* 2 * NetWinder Button Driver- 3 * Copyright (C) Alex Holden <alex@linuxhacker.org> 1998, 1999. 4 * 5 */ 6 7 #include <linux/module.h> 8 #include <linux/kernel.h> 9 #include <linux/sched.h> 10 #include <linux/interrupt.h> 11 #include <linux/time.h> 12 #include <linux/timer.h> 13 #include <linux/fs.h> 14 #include <linux/miscdevice.h> 15 #include <linux/string.h> 16 #include <linux/errno.h> 17 #include <linux/init.h> 18 19 #include <asm/uaccess.h> 20 #include <asm/irq.h> 21 #include <asm/mach-types.h> 22 23 #define __NWBUTTON_C /* Tell the header file who we are */ 24 #include "nwbutton.h" 25 26 static int button_press_count; /* The count of button presses */ 27 static struct timer_list button_timer; /* Times for the end of a sequence */ 28 static DECLARE_WAIT_QUEUE_HEAD(button_wait_queue); /* Used for blocking read */ 29 static char button_output_buffer[32]; /* Stores data to write out of device */ 30 static int bcount; /* The number of bytes in the buffer */ 31 static int bdelay = BUTTON_DELAY; /* The delay, in jiffies */ 32 static struct button_callback button_callback_list[32]; /* The callback list */ 33 static int callback_count; /* The number of callbacks registered */ 34 static int reboot_count = NUM_PRESSES_REBOOT; /* Number of presses to reboot */ 35 36 /* 37 * This function is called by other drivers to register a callback function 38 * to be called when a particular number of button presses occurs. 39 * The callback list is a static array of 32 entries (I somehow doubt many 40 * people are ever going to want to register more than 32 different actions 41 * to be performed by the kernel on different numbers of button presses ;). 42 * However, if an attempt to register a 33rd entry (perhaps a stuck loop 43 * somewhere registering the same entry over and over?) it will fail to 44 * do so and return -ENOMEM. If an attempt is made to register a null pointer, 45 * it will fail to do so and return -EINVAL. 46 * Because callbacks can be unregistered at random the list can become 47 * fragmented, so we need to search through the list until we find the first 48 * free entry. 49 * 50 * FIXME: Has anyone spotted any locking functions int his code recently ?? 51 */ 52 53 int button_add_callback (void (*callback) (void), int count) 54 { 55 int lp = 0; 56 if (callback_count == 32) { 57 return -ENOMEM; 58 } 59 if (!callback) { 60 return -EINVAL; 61 } 62 callback_count++; 63 for (; (button_callback_list [lp].callback); lp++); 64 button_callback_list [lp].callback = callback; 65 button_callback_list [lp].count = count; 66 return 0; 67 } 68 69 /* 70 * This function is called by other drivers to deregister a callback function. 71 * If you attempt to unregister a callback which does not exist, it will fail 72 * with -EINVAL. If there is more than one entry with the same address, 73 * because it searches the list from end to beginning, it will unregister the 74 * last one to be registered first (FILO- First In Last Out). 75 * Note that this is not neccessarily true if the entries are not submitted 76 * at the same time, because another driver could have unregistered a callback 77 * between the submissions creating a gap earlier in the list, which would 78 * be filled first at submission time. 79 */ 80 81 int button_del_callback (void (*callback) (void)) 82 { 83 int lp = 31; 84 if (!callback) { 85 return -EINVAL; 86 } 87 while (lp >= 0) { 88 if ((button_callback_list [lp].callback) == callback) { 89 button_callback_list [lp].callback = NULL; 90 button_callback_list [lp].count = 0; 91 callback_count--; 92 return 0; 93 }; 94 lp--; 95 }; 96 return -EINVAL; 97 } 98 99 /* 100 * This function is called by button_sequence_finished to search through the 101 * list of callback functions, and call any of them whose count argument 102 * matches the current count of button presses. It starts at the beginning 103 * of the list and works up to the end. It will refuse to follow a null 104 * pointer (which should never happen anyway). 105 */ 106 107 static void button_consume_callbacks (int bpcount) 108 { 109 int lp = 0; 110 for (; lp <= 31; lp++) { 111 if ((button_callback_list [lp].count) == bpcount) { 112 if (button_callback_list [lp].callback) { 113 button_callback_list[lp].callback(); 114 } 115 } 116 } 117 } 118 119 /* 120 * This function is called when the button_timer times out. 121 * ie. When you don't press the button for bdelay jiffies, this is taken to 122 * mean you have ended the sequence of key presses, and this function is 123 * called to wind things up (write the press_count out to /dev/button, call 124 * any matching registered function callbacks, initiate reboot, etc.). 125 */ 126 127 static void button_sequence_finished (unsigned long parameters) 128 { 129 #ifdef CONFIG_NWBUTTON_REBOOT /* Reboot using button is enabled */ 130 if (button_press_count == reboot_count) 131 kill_cad_pid(SIGINT, 1); /* Ask init to reboot us */ 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 irqreturn_t button_handler (int irq, void *dev_id) 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 return IRQ_HANDLED; 159 } 160 161 /* 162 * This function is called when a user space program attempts to read 163 * /dev/nwbutton. It puts the device to sleep on the wait queue until 164 * button_sequence_finished writes some data to the buffer and flushes 165 * the queue, at which point it writes the data out to the device and 166 * returns the number of characters it has written. This function is 167 * reentrant, so that many processes can be attempting to read from the 168 * device at any one time. 169 */ 170 171 static int button_read (struct file *filp, char __user *buffer, 172 size_t count, loff_t *ppos) 173 { 174 interruptible_sleep_on (&button_wait_queue); 175 return (copy_to_user (buffer, &button_output_buffer, bcount)) 176 ? -EFAULT : bcount; 177 } 178 179 /* 180 * This structure is the file operations structure, which specifies what 181 * callbacks functions the kernel should call when a user mode process 182 * attempts to perform these operations on the device. 183 */ 184 185 static const struct file_operations button_fops = { 186 .owner = THIS_MODULE, 187 .read = button_read, 188 }; 189 190 /* 191 * This structure is the misc device structure, which specifies the minor 192 * device number (158 in this case), the name of the device (for /proc/misc), 193 * and the address of the above file operations structure. 194 */ 195 196 static struct miscdevice button_misc_device = { 197 BUTTON_MINOR, 198 "nwbutton", 199 &button_fops, 200 }; 201 202 /* 203 * This function is called to initialise the driver, either from misc.c at 204 * bootup if the driver is compiled into the kernel, or from init_module 205 * below at module insert time. It attempts to register the device node 206 * and the IRQ and fails with a warning message if either fails, though 207 * neither ever should because the device number and IRQ are unique to 208 * this driver. 209 */ 210 211 static int __init nwbutton_init(void) 212 { 213 if (!machine_is_netwinder()) 214 return -ENODEV; 215 216 printk (KERN_INFO "NetWinder Button Driver Version %s (C) Alex Holden " 217 "<alex@linuxhacker.org> 1998.\n", VERSION); 218 219 if (misc_register (&button_misc_device)) { 220 printk (KERN_WARNING "nwbutton: Couldn't register device 10, " 221 "%d.\n", BUTTON_MINOR); 222 return -EBUSY; 223 } 224 225 if (request_irq (IRQ_NETWINDER_BUTTON, button_handler, IRQF_DISABLED, 226 "nwbutton", NULL)) { 227 printk (KERN_WARNING "nwbutton: IRQ %d is not free.\n", 228 IRQ_NETWINDER_BUTTON); 229 misc_deregister (&button_misc_device); 230 return -EIO; 231 } 232 return 0; 233 } 234 235 static void __exit nwbutton_exit (void) 236 { 237 free_irq (IRQ_NETWINDER_BUTTON, NULL); 238 misc_deregister (&button_misc_device); 239 } 240 241 242 MODULE_AUTHOR("Alex Holden"); 243 MODULE_LICENSE("GPL"); 244 245 module_init(nwbutton_init); 246 module_exit(nwbutton_exit); 247