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/signal.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 <linux/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 void button_sequence_finished(struct timer_list *unused); 27 28 static int button_press_count; /* The count of button presses */ 29 /* Times for the end of a sequence */ 30 static DEFINE_TIMER(button_timer, button_sequence_finished); 31 static DECLARE_WAIT_QUEUE_HEAD(button_wait_queue); /* Used for blocking read */ 32 static char button_output_buffer[32]; /* Stores data to write out of device */ 33 static int bcount; /* The number of bytes in the buffer */ 34 static int bdelay = BUTTON_DELAY; /* The delay, in jiffies */ 35 static struct button_callback button_callback_list[32]; /* The callback list */ 36 static int callback_count; /* The number of callbacks registered */ 37 static int reboot_count = NUM_PRESSES_REBOOT; /* Number of presses to reboot */ 38 39 /* 40 * This function is called by other drivers to register a callback function 41 * to be called when a particular number of button presses occurs. 42 * The callback list is a static array of 32 entries (I somehow doubt many 43 * people are ever going to want to register more than 32 different actions 44 * to be performed by the kernel on different numbers of button presses ;). 45 * However, if an attempt to register a 33rd entry (perhaps a stuck loop 46 * somewhere registering the same entry over and over?) it will fail to 47 * do so and return -ENOMEM. If an attempt is made to register a null pointer, 48 * it will fail to do so and return -EINVAL. 49 * Because callbacks can be unregistered at random the list can become 50 * fragmented, so we need to search through the list until we find the first 51 * free entry. 52 * 53 * FIXME: Has anyone spotted any locking functions int his code recently ?? 54 */ 55 56 int button_add_callback (void (*callback) (void), int count) 57 { 58 int lp = 0; 59 if (callback_count == 32) { 60 return -ENOMEM; 61 } 62 if (!callback) { 63 return -EINVAL; 64 } 65 callback_count++; 66 for (; (button_callback_list [lp].callback); lp++); 67 button_callback_list [lp].callback = callback; 68 button_callback_list [lp].count = count; 69 return 0; 70 } 71 72 /* 73 * This function is called by other drivers to deregister a callback function. 74 * If you attempt to unregister a callback which does not exist, it will fail 75 * with -EINVAL. If there is more than one entry with the same address, 76 * because it searches the list from end to beginning, it will unregister the 77 * last one to be registered first (FILO- First In Last Out). 78 * Note that this is not necessarily true if the entries are not submitted 79 * at the same time, because another driver could have unregistered a callback 80 * between the submissions creating a gap earlier in the list, which would 81 * be filled first at submission time. 82 */ 83 84 int button_del_callback (void (*callback) (void)) 85 { 86 int lp = 31; 87 if (!callback) { 88 return -EINVAL; 89 } 90 while (lp >= 0) { 91 if ((button_callback_list [lp].callback) == callback) { 92 button_callback_list [lp].callback = NULL; 93 button_callback_list [lp].count = 0; 94 callback_count--; 95 return 0; 96 } 97 lp--; 98 } 99 return -EINVAL; 100 } 101 102 /* 103 * This function is called by button_sequence_finished to search through the 104 * list of callback functions, and call any of them whose count argument 105 * matches the current count of button presses. It starts at the beginning 106 * of the list and works up to the end. It will refuse to follow a null 107 * pointer (which should never happen anyway). 108 */ 109 110 static void button_consume_callbacks (int bpcount) 111 { 112 int lp = 0; 113 for (; lp <= 31; lp++) { 114 if ((button_callback_list [lp].count) == bpcount) { 115 if (button_callback_list [lp].callback) { 116 button_callback_list[lp].callback(); 117 } 118 } 119 } 120 } 121 122 /* 123 * This function is called when the button_timer times out. 124 * ie. When you don't press the button for bdelay jiffies, this is taken to 125 * mean you have ended the sequence of key presses, and this function is 126 * called to wind things up (write the press_count out to /dev/button, call 127 * any matching registered function callbacks, initiate reboot, etc.). 128 */ 129 130 static void button_sequence_finished(struct timer_list *unused) 131 { 132 if (IS_ENABLED(CONFIG_NWBUTTON_REBOOT) && 133 button_press_count == reboot_count) 134 kill_cad_pid(SIGINT, 1); /* Ask init to reboot us */ 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) 150 { 151 button_press_count++; 152 mod_timer(&button_timer, jiffies + bdelay); 153 154 return IRQ_HANDLED; 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 __user *buffer, 168 size_t count, loff_t *ppos) 169 { 170 DEFINE_WAIT(wait); 171 prepare_to_wait(&button_wait_queue, &wait, TASK_INTERRUPTIBLE); 172 schedule(); 173 finish_wait(&button_wait_queue, &wait); 174 return (copy_to_user (buffer, &button_output_buffer, bcount)) 175 ? -EFAULT : bcount; 176 } 177 178 /* 179 * This structure is the file operations structure, which specifies what 180 * callbacks functions the kernel should call when a user mode process 181 * attempts to perform these operations on the device. 182 */ 183 184 static const struct file_operations button_fops = { 185 .owner = THIS_MODULE, 186 .read = button_read, 187 .llseek = noop_llseek, 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, 0, 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