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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 void button_sequence_finished (unsigned long parameters); | |
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, 0, 0); | |
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 (unsigned long parameters) | |
131 | { | |
132 | #ifdef CONFIG_NWBUTTON_REBOOT /* Reboot using button is enabled */ | |
133 | if (button_press_count == reboot_count) | |
134 | kill_cad_pid(SIGINT, 1); /* Ask init to reboot us */ | |
135 | #endif /* CONFIG_NWBUTTON_REBOOT */ | |
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 | interruptible_sleep_on (&button_wait_queue); | |
172 | return (copy_to_user (buffer, &button_output_buffer, bcount)) | |
173 | ? -EFAULT : bcount; | |
174 | } | |
175 | ||
176 | /* | |
177 | * This structure is the file operations structure, which specifies what | |
178 | * callbacks functions the kernel should call when a user mode process | |
179 | * attempts to perform these operations on the device. | |
180 | */ | |
181 | ||
182 | static const struct file_operations button_fops = { | |
183 | .owner = THIS_MODULE, | |
184 | .read = button_read, | |
185 | .llseek = noop_llseek, | |
186 | }; | |
187 | ||
188 | /* | |
189 | * This structure is the misc device structure, which specifies the minor | |
190 | * device number (158 in this case), the name of the device (for /proc/misc), | |
191 | * and the address of the above file operations structure. | |
192 | */ | |
193 | ||
194 | static struct miscdevice button_misc_device = { | |
195 | BUTTON_MINOR, | |
196 | "nwbutton", | |
197 | &button_fops, | |
198 | }; | |
199 | ||
200 | /* | |
201 | * This function is called to initialise the driver, either from misc.c at | |
202 | * bootup if the driver is compiled into the kernel, or from init_module | |
203 | * below at module insert time. It attempts to register the device node | |
204 | * and the IRQ and fails with a warning message if either fails, though | |
205 | * neither ever should because the device number and IRQ are unique to | |
206 | * this driver. | |
207 | */ | |
208 | ||
209 | static int __init nwbutton_init(void) | |
210 | { | |
211 | if (!machine_is_netwinder()) | |
212 | return -ENODEV; | |
213 | ||
214 | printk (KERN_INFO "NetWinder Button Driver Version %s (C) Alex Holden " | |
215 | "<alex@linuxhacker.org> 1998.\n", VERSION); | |
216 | ||
217 | if (misc_register (&button_misc_device)) { | |
218 | printk (KERN_WARNING "nwbutton: Couldn't register device 10, " | |
219 | "%d.\n", BUTTON_MINOR); | |
220 | return -EBUSY; | |
221 | } | |
222 | ||
223 | if (request_irq (IRQ_NETWINDER_BUTTON, button_handler, IRQF_DISABLED, | |
224 | "nwbutton", NULL)) { | |
225 | printk (KERN_WARNING "nwbutton: IRQ %d is not free.\n", | |
226 | IRQ_NETWINDER_BUTTON); | |
227 | misc_deregister (&button_misc_device); | |
228 | return -EIO; | |
229 | } | |
230 | return 0; | |
231 | } | |
232 | ||
233 | static void __exit nwbutton_exit (void) | |
234 | { | |
235 | free_irq (IRQ_NETWINDER_BUTTON, NULL); | |
236 | misc_deregister (&button_misc_device); | |
237 | } | |
238 | ||
239 | ||
240 | MODULE_AUTHOR("Alex Holden"); | |
241 | MODULE_LICENSE("GPL"); | |
242 | ||
243 | module_init(nwbutton_init); | |
244 | module_exit(nwbutton_exit); |