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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * NetWinder Button Driver-4 * Copyright (C) Alex Holden <alex@linuxhacker.org> 1998, 1999.5 *6 */7 8#include <linux/module.h>9#include <linux/kernel.h>10#include <linux/sched/signal.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 <linux/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 27static void button_sequence_finished(struct timer_list *unused);28 29static int button_press_count; /* The count of button presses */30/* Times for the end of a sequence */31static DEFINE_TIMER(button_timer, button_sequence_finished);32static DECLARE_WAIT_QUEUE_HEAD(button_wait_queue); /* Used for blocking read */33static char button_output_buffer[32]; /* Stores data to write out of device */34static int bcount; /* The number of bytes in the buffer */35static int bdelay = BUTTON_DELAY; /* The delay, in jiffies */36static struct button_callback button_callback_list[32]; /* The callback list */37static int callback_count; /* The number of callbacks registered */38static int reboot_count = NUM_PRESSES_REBOOT; /* Number of presses to reboot */39 40/*41 * This function is called by other drivers to register a callback function42 * to be called when a particular number of button presses occurs.43 * The callback list is a static array of 32 entries (I somehow doubt many44 * people are ever going to want to register more than 32 different actions45 * to be performed by the kernel on different numbers of button presses ;).46 * However, if an attempt to register a 33rd entry (perhaps a stuck loop47 * somewhere registering the same entry over and over?) it will fail to48 * do so and return -ENOMEM. If an attempt is made to register a null pointer,49 * it will fail to do so and return -EINVAL.50 * Because callbacks can be unregistered at random the list can become51 * fragmented, so we need to search through the list until we find the first52 * free entry.53 *54 * FIXME: Has anyone spotted any locking functions int his code recently ??55 */56 57int button_add_callback (void (*callback) (void), int count)58{59 int lp = 0;60 if (callback_count == 32) {61 return -ENOMEM;62 }63 if (!callback) {64 return -EINVAL;65 }66 callback_count++;67 for (; (button_callback_list [lp].callback); lp++);68 button_callback_list [lp].callback = callback;69 button_callback_list [lp].count = count;70 return 0;71}72 73/*74 * This function is called by other drivers to deregister a callback function.75 * If you attempt to unregister a callback which does not exist, it will fail76 * with -EINVAL. If there is more than one entry with the same address,77 * because it searches the list from end to beginning, it will unregister the78 * last one to be registered first (FILO- First In Last Out).79 * Note that this is not necessarily true if the entries are not submitted80 * at the same time, because another driver could have unregistered a callback81 * between the submissions creating a gap earlier in the list, which would82 * be filled first at submission time.83 */84 85int button_del_callback (void (*callback) (void))86{87 int lp = 31;88 if (!callback) {89 return -EINVAL;90 }91 while (lp >= 0) {92 if ((button_callback_list [lp].callback) == callback) {93 button_callback_list [lp].callback = NULL;94 button_callback_list [lp].count = 0;95 callback_count--;96 return 0;97 }98 lp--;99 }100 return -EINVAL;101}102 103/*104 * This function is called by button_sequence_finished to search through the105 * list of callback functions, and call any of them whose count argument106 * matches the current count of button presses. It starts at the beginning107 * of the list and works up to the end. It will refuse to follow a null108 * pointer (which should never happen anyway).109 */110 111static void button_consume_callbacks (int bpcount)112{113 int lp = 0;114 for (; lp <= 31; lp++) {115 if ((button_callback_list [lp].count) == bpcount) {116 if (button_callback_list [lp].callback) {117 button_callback_list[lp].callback();118 }119 }120 }121}122 123/* 124 * This function is called when the button_timer times out.125 * ie. When you don't press the button for bdelay jiffies, this is taken to126 * mean you have ended the sequence of key presses, and this function is127 * called to wind things up (write the press_count out to /dev/button, call128 * any matching registered function callbacks, initiate reboot, etc.).129 */130 131static void button_sequence_finished(struct timer_list *unused)132{133 if (IS_ENABLED(CONFIG_NWBUTTON_REBOOT) &&134 button_press_count == reboot_count)135 kill_cad_pid(SIGINT, 1); /* Ask init to reboot us */136 button_consume_callbacks (button_press_count);137 bcount = sprintf (button_output_buffer, "%d\n", button_press_count);138 button_press_count = 0; /* Reset the button press counter */139 wake_up_interruptible (&button_wait_queue);140}141 142/* 143 * This handler is called when the orange button is pressed (GPIO 10 of the144 * SuperIO chip, which maps to logical IRQ 26). If the press_count is 0,145 * this is the first press, so it starts a timer and increments the counter.146 * If it is higher than 0, it deletes the old timer, starts a new one, and147 * increments the counter.148 */ 149 150static irqreturn_t button_handler (int irq, void *dev_id)151{152 button_press_count++;153 mod_timer(&button_timer, jiffies + bdelay);154 155 return IRQ_HANDLED;156}157 158/*159 * This function is called when a user space program attempts to read160 * /dev/nwbutton. It puts the device to sleep on the wait queue until161 * button_sequence_finished writes some data to the buffer and flushes162 * the queue, at which point it writes the data out to the device and163 * returns the number of characters it has written. This function is164 * reentrant, so that many processes can be attempting to read from the165 * device at any one time.166 */167 168static int button_read (struct file *filp, char __user *buffer,169 size_t count, loff_t *ppos)170{171 DEFINE_WAIT(wait);172 prepare_to_wait(&button_wait_queue, &wait, TASK_INTERRUPTIBLE);173 schedule();174 finish_wait(&button_wait_queue, &wait);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 what181 * callbacks functions the kernel should call when a user mode process182 * attempts to perform these operations on the device.183 */184 185static const struct file_operations button_fops = {186 .owner = THIS_MODULE,187 .read = button_read,188 .llseek = noop_llseek,189};190 191/* 192 * This structure is the misc device structure, which specifies the minor193 * device number (158 in this case), the name of the device (for /proc/misc),194 * and the address of the above file operations structure.195 */196 197static struct miscdevice button_misc_device = {198 BUTTON_MINOR,199 "nwbutton",200 &button_fops,201};202 203/*204 * This function is called to initialise the driver, either from misc.c at205 * bootup if the driver is compiled into the kernel, or from init_module206 * below at module insert time. It attempts to register the device node207 * and the IRQ and fails with a warning message if either fails, though208 * neither ever should because the device number and IRQ are unique to209 * this driver.210 */211 212static int __init nwbutton_init(void)213{214 if (!machine_is_netwinder())215 return -ENODEV;216 217 printk (KERN_INFO "NetWinder Button Driver Version %s (C) Alex Holden "218 "<alex@linuxhacker.org> 1998.\n", VERSION);219 220 if (misc_register (&button_misc_device)) {221 printk (KERN_WARNING "nwbutton: Couldn't register device 10, "222 "%d.\n", BUTTON_MINOR);223 return -EBUSY;224 }225 226 if (request_irq (IRQ_NETWINDER_BUTTON, button_handler, 0,227 "nwbutton", NULL)) {228 printk (KERN_WARNING "nwbutton: IRQ %d is not free.\n",229 IRQ_NETWINDER_BUTTON);230 misc_deregister (&button_misc_device);231 return -EIO;232 }233 return 0;234}235 236static void __exit nwbutton_exit (void) 237{238 free_irq (IRQ_NETWINDER_BUTTON, NULL);239 misc_deregister (&button_misc_device);240}241 242 243MODULE_AUTHOR("Alex Holden");244MODULE_DESCRIPTION("NetWinder button driver");245MODULE_LICENSE("GPL");246 247module_init(nwbutton_init);248module_exit(nwbutton_exit);249