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/drivers/char/nwbutton.c

https://bitbucket.org/evzijst/gittest
C | 248 lines | 138 code | 30 blank | 80 comment | 18 complexity | 9a0d399f2e9223b37925ab86f5cbbe8f MD5 | raw file
  1/*
  2 * 	NetWinder Button Driver-
  3 *	Copyright (C) Alex Holden <alex@linuxhacker.org> 1998, 1999.
  4 *
  5 */
  6
  7#include <linux/config.h>
  8#include <linux/module.h>
  9#include <linux/kernel.h>
 10#include <linux/sched.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 <asm/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 int button_press_count;		/* The count of button presses */
 28static struct timer_list button_timer;	/* Times for the end of a sequence */ 
 29static DECLARE_WAIT_QUEUE_HEAD(button_wait_queue); /* Used for blocking read */
 30static char button_output_buffer[32];	/* Stores data to write out of device */
 31static int bcount;			/* The number of bytes in the buffer */
 32static int bdelay = BUTTON_DELAY;	/* The delay, in jiffies */
 33static struct button_callback button_callback_list[32]; /* The callback list */
 34static int callback_count;		/* The number of callbacks registered */
 35static int reboot_count = NUM_PRESSES_REBOOT; /* Number of presses to reboot */
 36
 37/*
 38 * This function is called by other drivers to register a callback function
 39 * to be called when a particular number of button presses occurs.
 40 * The callback list is a static array of 32 entries (I somehow doubt many
 41 * people are ever going to want to register more than 32 different actions
 42 * to be performed by the kernel on different numbers of button presses ;).
 43 * However, if an attempt to register a 33rd entry (perhaps a stuck loop
 44 * somewhere registering the same entry over and over?) it will fail to
 45 * do so and return -ENOMEM. If an attempt is made to register a null pointer,
 46 * it will fail to do so and return -EINVAL.
 47 * Because callbacks can be unregistered at random the list can become
 48 * fragmented, so we need to search through the list until we find the first
 49 * free entry.
 50 *
 51 * FIXME: Has anyone spotted any locking functions int his code recently ??
 52 */
 53
 54int button_add_callback (void (*callback) (void), int count)
 55{
 56	int lp = 0;
 57	if (callback_count == 32) {
 58		return -ENOMEM;
 59	}
 60	if (!callback) {
 61		return -EINVAL;
 62	}
 63	callback_count++;
 64	for (; (button_callback_list [lp].callback); lp++);
 65	button_callback_list [lp].callback = callback;
 66	button_callback_list [lp].count = count;
 67	return 0;
 68}
 69
 70/*
 71 * This function is called by other drivers to deregister a callback function.
 72 * If you attempt to unregister a callback which does not exist, it will fail
 73 * with -EINVAL. If there is more than one entry with the same address,
 74 * because it searches the list from end to beginning, it will unregister the
 75 * last one to be registered first (FILO- First In Last Out).
 76 * Note that this is not neccessarily true if the entries are not submitted
 77 * at the same time, because another driver could have unregistered a callback
 78 * between the submissions creating a gap earlier in the list, which would
 79 * be filled first at submission time.
 80 */
 81
 82int button_del_callback (void (*callback) (void))
 83{
 84	int lp = 31;
 85	if (!callback) {
 86		return -EINVAL;
 87	}
 88	while (lp >= 0) {
 89		if ((button_callback_list [lp].callback) == callback) {
 90			button_callback_list [lp].callback = NULL;
 91			button_callback_list [lp].count = 0;
 92			callback_count--;
 93			return 0;
 94		};
 95		lp--;
 96	};
 97	return -EINVAL;
 98}
 99
100/*
101 * This function is called by button_sequence_finished to search through the
102 * list of callback functions, and call any of them whose count argument
103 * matches the current count of button presses. It starts at the beginning
104 * of the list and works up to the end. It will refuse to follow a null
105 * pointer (which should never happen anyway).
106 */
107
108static void button_consume_callbacks (int bpcount)
109{
110	int lp = 0;
111	for (; lp <= 31; lp++) {
112		if ((button_callback_list [lp].count) == bpcount) {
113			if (button_callback_list [lp].callback) {
114				button_callback_list[lp].callback();
115			}
116		}
117	}
118}
119
120/* 
121 * This function is called when the button_timer times out.
122 * ie. When you don't press the button for bdelay jiffies, this is taken to
123 * mean you have ended the sequence of key presses, and this function is
124 * called to wind things up (write the press_count out to /dev/button, call
125 * any matching registered function callbacks, initiate reboot, etc.).
126 */
127
128static void button_sequence_finished (unsigned long parameters)
129{
130#ifdef CONFIG_NWBUTTON_REBOOT		/* Reboot using button is enabled */
131	if (button_press_count == reboot_count) {
132		kill_proc (1, SIGINT, 1);	/* Ask init to reboot us */
133	}
134#endif /* CONFIG_NWBUTTON_REBOOT */
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
149static irqreturn_t button_handler (int irq, void *dev_id, struct pt_regs *regs)
150{
151	if (button_press_count) {
152		del_timer (&button_timer);
153	}
154	button_press_count++;
155	init_timer (&button_timer);
156	button_timer.function = button_sequence_finished;
157	button_timer.expires = (jiffies + bdelay);
158	add_timer (&button_timer);
159
160	return IRQ_HANDLED;
161}
162
163/*
164 * This function is called when a user space program attempts to read
165 * /dev/nwbutton. It puts the device to sleep on the wait queue until
166 * button_sequence_finished writes some data to the buffer and flushes
167 * the queue, at which point it writes the data out to the device and
168 * returns the number of characters it has written. This function is
169 * reentrant, so that many processes can be attempting to read from the
170 * device at any one time.
171 */
172
173static int button_read (struct file *filp, char __user *buffer,
174			size_t count, loff_t *ppos)
175{
176	interruptible_sleep_on (&button_wait_queue);
177	return (copy_to_user (buffer, &button_output_buffer, bcount))
178		 ? -EFAULT : bcount;
179}
180
181/* 
182 * This structure is the file operations structure, which specifies what
183 * callbacks functions the kernel should call when a user mode process
184 * attempts to perform these operations on the device.
185 */
186
187static struct file_operations button_fops = {
188	.owner		= THIS_MODULE,
189	.read		= button_read,
190};
191
192/* 
193 * This structure is the misc device structure, which specifies the minor
194 * device number (158 in this case), the name of the device (for /proc/misc),
195 * and the address of the above file operations structure.
196 */
197
198static struct miscdevice button_misc_device = {
199	BUTTON_MINOR,
200	"nwbutton",
201	&button_fops,
202};
203
204/*
205 * This function is called to initialise the driver, either from misc.c at
206 * bootup if the driver is compiled into the kernel, or from init_module
207 * below at module insert time. It attempts to register the device node
208 * and the IRQ and fails with a warning message if either fails, though
209 * neither ever should because the device number and IRQ are unique to
210 * this driver.
211 */
212
213static int __init nwbutton_init(void)
214{
215	if (!machine_is_netwinder())
216		return -ENODEV;
217
218	printk (KERN_INFO "NetWinder Button Driver Version %s (C) Alex Holden "
219			"<alex@linuxhacker.org> 1998.\n", VERSION);
220
221	if (misc_register (&button_misc_device)) {
222		printk (KERN_WARNING "nwbutton: Couldn't register device 10, "
223				"%d.\n", BUTTON_MINOR);
224		return -EBUSY;
225	}
226
227	if (request_irq (IRQ_NETWINDER_BUTTON, button_handler, SA_INTERRUPT,
228			"nwbutton", NULL)) {
229		printk (KERN_WARNING "nwbutton: IRQ %d is not free.\n",
230				IRQ_NETWINDER_BUTTON);
231		misc_deregister (&button_misc_device);
232		return -EIO;
233	}
234	return 0;
235}
236
237static void __exit nwbutton_exit (void) 
238{
239	free_irq (IRQ_NETWINDER_BUTTON, NULL);
240	misc_deregister (&button_misc_device);
241}
242
243
244MODULE_AUTHOR("Alex Holden");
245MODULE_LICENSE("GPL");
246
247module_init(nwbutton_init);
248module_exit(nwbutton_exit);