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/signal.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 <linux/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(struct timer_list *unused);
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);
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 
button_add_callback(void (* callback)(void),int count)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 
button_del_callback(void (* callback)(void))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 
button_consume_callbacks(int bpcount)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 
button_sequence_finished(struct timer_list * unused)130 static void button_sequence_finished(struct timer_list *unused)
131 {
132 	if (IS_ENABLED(CONFIG_NWBUTTON_REBOOT) &&
133 	    button_press_count == reboot_count)
134 		kill_cad_pid(SIGINT, 1);	/* Ask init to reboot us */
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 
button_handler(int irq,void * dev_id)149 static irqreturn_t button_handler (int irq, void *dev_id)
150 {
151 	button_press_count++;
152 	mod_timer(&button_timer, jiffies + bdelay);
153 
154 	return IRQ_HANDLED;
155 }
156 
157 /*
158  * This function is called when a user space program attempts to read
159  * /dev/nwbutton. It puts the device to sleep on the wait queue until
160  * button_sequence_finished writes some data to the buffer and flushes
161  * the queue, at which point it writes the data out to the device and
162  * returns the number of characters it has written. This function is
163  * reentrant, so that many processes can be attempting to read from the
164  * device at any one time.
165  */
166 
button_read(struct file * filp,char __user * buffer,size_t count,loff_t * ppos)167 static int button_read (struct file *filp, char __user *buffer,
168 			size_t count, loff_t *ppos)
169 {
170 	DEFINE_WAIT(wait);
171 	prepare_to_wait(&button_wait_queue, &wait, TASK_INTERRUPTIBLE);
172 	schedule();
173 	finish_wait(&button_wait_queue, &wait);
174 	return (copy_to_user (buffer, &button_output_buffer, bcount))
175 		 ? -EFAULT : bcount;
176 }
177 
178 /*
179  * This structure is the file operations structure, which specifies what
180  * callbacks functions the kernel should call when a user mode process
181  * attempts to perform these operations on the device.
182  */
183 
184 static const struct file_operations button_fops = {
185 	.owner		= THIS_MODULE,
186 	.read		= button_read,
187 	.llseek		= noop_llseek,
188 };
189 
190 /*
191  * This structure is the misc device structure, which specifies the minor
192  * device number (158 in this case), the name of the device (for /proc/misc),
193  * and the address of the above file operations structure.
194  */
195 
196 static struct miscdevice button_misc_device = {
197 	BUTTON_MINOR,
198 	"nwbutton",
199 	&button_fops,
200 };
201 
202 /*
203  * This function is called to initialise the driver, either from misc.c at
204  * bootup if the driver is compiled into the kernel, or from init_module
205  * below at module insert time. It attempts to register the device node
206  * and the IRQ and fails with a warning message if either fails, though
207  * neither ever should because the device number and IRQ are unique to
208  * this driver.
209  */
210 
nwbutton_init(void)211 static int __init nwbutton_init(void)
212 {
213 	if (!machine_is_netwinder())
214 		return -ENODEV;
215 
216 	printk (KERN_INFO "NetWinder Button Driver Version %s (C) Alex Holden "
217 			"<alex@linuxhacker.org> 1998.\n", VERSION);
218 
219 	if (misc_register (&button_misc_device)) {
220 		printk (KERN_WARNING "nwbutton: Couldn't register device 10, "
221 				"%d.\n", BUTTON_MINOR);
222 		return -EBUSY;
223 	}
224 
225 	if (request_irq (IRQ_NETWINDER_BUTTON, button_handler, 0,
226 			"nwbutton", NULL)) {
227 		printk (KERN_WARNING "nwbutton: IRQ %d is not free.\n",
228 				IRQ_NETWINDER_BUTTON);
229 		misc_deregister (&button_misc_device);
230 		return -EIO;
231 	}
232 	return 0;
233 }
234 
nwbutton_exit(void)235 static void __exit nwbutton_exit (void)
236 {
237 	free_irq (IRQ_NETWINDER_BUTTON, NULL);
238 	misc_deregister (&button_misc_device);
239 }
240 
241 
242 MODULE_AUTHOR("Alex Holden");
243 MODULE_LICENSE("GPL");
244 
245 module_init(nwbutton_init);
246 module_exit(nwbutton_exit);
247