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, priv: 1); /* Ask init to reboot us */ |
136 | button_consume_callbacks (bpcount: button_press_count); |
137 | bcount = sprintf (buf: button_output_buffer, fmt: "%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(timer: &button_timer, expires: 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(wq_head: &button_wait_queue, wq_entry: &wait, TASK_INTERRUPTIBLE); |
173 | schedule(); |
174 | finish_wait(wq_head: &button_wait_queue, wq_entry: &wait); |
175 | return (copy_to_user (to: buffer, from: &button_output_buffer, n: 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 (misc: &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: IRQ_NETWINDER_BUTTON, handler: button_handler, flags: 0, |
227 | name: "nwbutton" , NULL)) { |
228 | printk (KERN_WARNING "nwbutton: IRQ %d is not free.\n" , |
229 | IRQ_NETWINDER_BUTTON); |
230 | misc_deregister (misc: &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 (misc: &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); |
248 | |