1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
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
27 static void button_sequence_finished(struct timer_list *unused);
28
29 static int button_press_count; /* The count of button presses */
30 /* Times for the end of a sequence */
31 static DEFINE_TIMER(button_timer, button_sequence_finished);
32 static DECLARE_WAIT_QUEUE_HEAD(button_wait_queue); /* Used for blocking read */
33 static char button_output_buffer[32]; /* Stores data to write out of device */
34 static int bcount; /* The number of bytes in the buffer */
35 static int bdelay = BUTTON_DELAY; /* The delay, in jiffies */
36 static struct button_callback button_callback_list[32]; /* The callback list */
37 static int callback_count; /* The number of callbacks registered */
38 static 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 function
42 * 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 many
44 * people are ever going to want to register more than 32 different actions
45 * 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 loop
47 * somewhere registering the same entry over and over?) it will fail to
48 * 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 become
51 * fragmented, so we need to search through the list until we find the first
52 * free entry.
53 *
54 * FIXME: Has anyone spotted any locking functions int his code recently ??
55 */
56
57 int 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 fail
76 * 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 the
78 * last one to be registered first (FILO- First In Last Out).
79 * Note that this is not necessarily true if the entries are not submitted
80 * at the same time, because another driver could have unregistered a callback
81 * between the submissions creating a gap earlier in the list, which would
82 * be filled first at submission time.
83 */
84
85 int 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 the
105 * list of callback functions, and call any of them whose count argument
106 * matches the current count of button presses. It starts at the beginning
107 * of the list and works up to the end. It will refuse to follow a null
108 * pointer (which should never happen anyway).
109 */
110
111 static 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 to
126 * mean you have ended the sequence of key presses, and this function is
127 * called to wind things up (write the press_count out to /dev/button, call
128 * any matching registered function callbacks, initiate reboot, etc.).
129 */
130
131 static 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 the
144 * 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, and
147 * increments the counter.
148 */
149
150 static 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 read
160 * /dev/nwbutton. It puts the device to sleep on the wait queue until
161 * button_sequence_finished writes some data to the buffer and flushes
162 * the queue, at which point it writes the data out to the device and
163 * returns the number of characters it has written. This function is
164 * reentrant, so that many processes can be attempting to read from the
165 * device at any one time.
166 */
167
168 static 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 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 .llseek = noop_llseek,
189 };
190
191 /*
192 * This structure is the misc device structure, which specifies the minor
193 * 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
197 static 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 at
205 * bootup if the driver is compiled into the kernel, or from init_module
206 * below at module insert time. It attempts to register the device node
207 * and the IRQ and fails with a warning message if either fails, though
208 * neither ever should because the device number and IRQ are unique to
209 * this driver.
210 */
211
212 static 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
236 static void __exit nwbutton_exit (void)
237 {
238 free_irq (IRQ_NETWINDER_BUTTON, NULL);
239 misc_deregister (&button_misc_device);
240 }
241
242
243 MODULE_AUTHOR("Alex Holden");
244 MODULE_LICENSE("GPL");
245
246 module_init(nwbutton_init);
247 module_exit(nwbutton_exit);