patch-2.3.48 linux/drivers/char/nwbutton.c

• Lines: 277
• Date: Thu Feb 24 22:56:47 2000
• Orig file: v2.3.47/linux/drivers/char/nwbutton.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.3.47/linux/drivers/char/nwbutton.c linux/drivers/char/nwbutton.c
@@ -0,0 +1,276 @@
+/*
+ * 	NetWinder Button Driver-
+ *	Copyright (C) Alex Holden <alex@linuxhacker.org> 1998, 1999.
+ *
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/interrupt.h>
+#include <linux/time.h>
+#include <linux/timer.h>
+#include <linux/fs.h>
+#include <linux/miscdevice.h>
+#include <linux/string.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+
+#include <asm/uaccess.h>
+#include <asm/irq.h>
+#define __NWBUTTON_C		/* Tell the header file who we are */
+#include "nwbutton.h"
+
+static int button_press_count = 0;	/* The count of button presses */
+static struct timer_list button_timer;	/* Times for the end of a sequence */ 
+static DECLARE_WAIT_QUEUE_HEAD(button_wait_queue); /* Used for blocking read */
+static char button_output_buffer[32];	/* Stores data to write out of device */
+static int bcount = 0;			/* The number of bytes in the buffer */
+static int bdelay = BUTTON_DELAY;	/* The delay, in jiffies */
+static struct button_callback button_callback_list[32]; /* The callback list */
+static int callback_count = 0;		/* The number of callbacks registered */
+static int reboot_count = NUM_PRESSES_REBOOT; /* Number of presses to reboot */
+
+/*
+ * This function is called by other drivers to register a callback function
+ * to be called when a particular number of button presses occurs.
+ * The callback list is a static array of 32 entries (I somehow doubt many
+ * people are ever going to want to register more than 32 different actions
+ * to be performed by the kernel on different numbers of button presses ;).
+ * However, if an attempt to register a 33rd entry (perhaps a stuck loop
+ * somewhere registering the same entry over and over?) it will fail to
+ * do so and return -ENOMEM. If an attempt is made to register a null pointer,
+ * it will fail to do so and return -EINVAL.
+ * Because callbacks can be unregistered at random the list can become
+ * fragmented, so we need to search through the list until we find the first
+ * free entry.
+ */
+
+int button_add_callback (void (*callback) (void), int count)
+{
+	int lp = 0;
+	if (callback_count == 32) {
+		return -ENOMEM;
+	}
+	if (!callback) {
+		return -EINVAL;
+	}
+	callback_count++;
+	for (; (button_callback_list [lp].callback); lp++);
+	button_callback_list [lp].callback = callback;
+	button_callback_list [lp].count = count;
+	return 0;
+}
+
+/*
+ * This function is called by other drivers to deregister a callback function.
+ * If you attempt to unregister a callback which does not exist, it will fail
+ * with -EINVAL. If there is more than one entry with the same address,
+ * because it searches the list from end to beginning, it will unregister the
+ * last one to be registered first (FILO- First In Last Out).
+ * Note that this is not neccessarily true if the entries are not submitted
+ * at the same time, because another driver could have unregistered a callback
+ * between the submissions creating a gap earlier in the list, which would
+ * be filled first at submission time.
+ */
+
+int button_del_callback (void (*callback) (void))
+{
+	int lp = 31;
+	if (!callback) {
+		return -EINVAL;
+	}
+	while (lp >= 0) {
+		if ((button_callback_list [lp].callback) == callback) {
+			button_callback_list [lp].callback = NULL;
+			button_callback_list [lp].count = 0;
+			callback_count--;
+			return 0;
+		};
+		lp--;
+	};
+	return -EINVAL;
+}
+
+/*
+ * This function is called by button_sequence_finished to search through the
+ * list of callback functions, and call any of them whose count argument
+ * matches the current count of button presses. It starts at the beginning
+ * of the list and works up to the end. It will refuse to follow a null
+ * pointer (which should never happen anyway).
+ */
+
+static void button_consume_callbacks (int bpcount)
+{
+	int lp = 0;
+	for (; lp <= 31; lp++) {
+		if ((button_callback_list [lp].count) == bpcount) {
+			if (button_callback_list [lp].callback) {
+				button_callback_list[lp].callback();
+			}
+		}
+	}
+}
+
+/* 
+ * This function is called when the button_timer times out.
+ * ie. When you don't press the button for bdelay jiffies, this is taken to
+ * mean you have ended the sequence of key presses, and this function is
+ * called to wind things up (write the press_count out to /dev/button, call
+ * any matching registered function callbacks, initiate reboot, etc.).
+ */
+
+static void button_sequence_finished (unsigned long parameters)
+{
+#ifdef CONFIG_NWBUTTON_REBOOT		/* Reboot using button is enabled */
+	if (button_press_count == reboot_count) {
+		kill_proc (1, SIGINT, 1);	/* Ask init to reboot us */
+	}
+#endif /* CONFIG_NWBUTTON_REBOOT */
+	button_consume_callbacks (button_press_count);
+	bcount = sprintf (button_output_buffer, "%d\n", button_press_count);
+	button_press_count = 0;		/* Reset the button press counter */
+	wake_up_interruptible (&button_wait_queue);
+}
+
+/* 
+ *  This handler is called when the orange button is pressed (GPIO 10 of the
+ *  SuperIO chip, which maps to logical IRQ 26). If the press_count is 0,
+ *  this is the first press, so it starts a timer and increments the counter.
+ *  If it is higher than 0, it deletes the old timer, starts a new one, and
+ *  increments the counter.
+ */ 
+
+static void button_handler (int irq, void *dev_id, struct pt_regs *regs)
+{
+	if (button_press_count) {
+		del_timer (&button_timer);
+	}
+	button_press_count++;
+	init_timer (&button_timer);
+	button_timer.function = button_sequence_finished;
+	button_timer.expires = (jiffies + bdelay);
+	add_timer (&button_timer);
+}
+
+/*
+ * This function is called when a user space program attempts to read
+ * /dev/nwbutton. It puts the device to sleep on the wait queue until
+ * button_sequence_finished writes some data to the buffer and flushes
+ * the queue, at which point it writes the data out to the device and
+ * returns the number of characters it has written. This function is
+ * reentrant, so that many processes can be attempting to read from the
+ * device at any one time.
+ */
+
+static int button_read (struct file *filp, char *buffer,
+			size_t count, loff_t *ppos)
+{
+	interruptible_sleep_on (&button_wait_queue);
+	return (copy_to_user (buffer, &button_output_buffer, bcount))
+		 ? -EFAULT : bcount;
+}
+
+/*
+ * This function is called when a user space process attempts to open the
+ * device. If the driver is compiled into the kernel it does nothing but
+ * succeed, but if it is compiled in as a module it also increments the
+ * module usage count to prevent the module from being removed whilst a
+ * process has the device open.
+ */
+
+static int button_open (struct inode *inode, struct file *filp)
+{
+	MOD_INC_USE_COUNT;
+	return 0;
+}
+
+/*
+ * This function is called when a user space process attempts to close the
+ * device. If the driver is compiled into the kernel it does nothing at all,
+ * but if it is compiled in as a module it also decrements the module usage
+ * count so that it will be possible to unload the module again once all the
+ * user processes have closed the device.
+ */
+
+static int button_release (struct inode *inode, struct file *filp)
+{
+	MOD_DEC_USE_COUNT;
+	return 0;
+}
+
+/* 
+ * This structure is the file operations structure, which specifies what
+ * callbacks functions the kernel should call when a user mode process
+ * attempts to perform these operations on the device.
+ */
+
+static struct file_operations button_fops = {
+	NULL,		/* lseek */
+	button_read,
+	NULL,		/* write */
+	NULL,		/* readdir */
+	NULL,		/* select */
+	NULL,		/* ioctl */
+	NULL,		/* mmap */
+	button_open,
+	NULL,		/* flush */
+	button_release,
+};
+
+/* 
+ * This structure is the misc device structure, which specifies the minor
+ * device number (158 in this case), the name of the device (for /proc/misc),
+ * and the address of the above file operations structure.
+ */
+
+static struct miscdevice button_misc_device = {
+	BUTTON_MINOR,
+	"nwbutton",
+	&button_fops,
+};
+
+/*
+ * This function is called to initialise the driver, either from misc.c at
+ * bootup if the driver is compiled into the kernel, or from init_module
+ * below at module insert time. It attempts to register the device node
+ * and the IRQ and fails with a warning message if either fails, though
+ * neither ever should because the device number and IRQ are unique to
+ * this driver.
+ */
+
+static int __init nwbutton_init(void)
+{
+	if (!machine_is_netwinder())
+		return -ENODEV;
+
+	printk (KERN_INFO "NetWinder Button Driver Version %s (C) Alex Holden "
+			"<alex@linuxhacker.org> 1998.\n", VERSION);
+
+	if (misc_register (&button_misc_device)) {
+		printk (KERN_WARNING "nwbutton: Couldn't register device 10, "
+				"%d.\n", BUTTON_MINOR);
+		return -EBUSY;
+	}
+
+	if (request_irq (IRQ_NETWINDER_BUTTON, button_handler, SA_INTERRUPT,
+			"nwbutton", NULL)) {
+		printk (KERN_WARNING "nwbutton: IRQ %d is not free.\n",
+				IRQ_NETWINDER_BUTTON);
+		misc_deregister (&button_misc_device);
+		return -EIO;
+	}
+	return 0;
+}
+
+static void __exit nwbutton_exit (void) 
+{
+	free_irq (IRQ_NETWINDER_BUTTON, NULL);
+	misc_deregister (&button_misc_device);
+}
+
+EXPORT_NO_SYMBOLS;
+
+module_init(nwbutton_init);
+module_exit(nwbutton_exit);