drivers/char/nwbutton.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * 	NetWinder Button Driver-
  *	Copyright (C) Alex Holden <alex@linuxhacker.org> 1998, 1999.
  *
  */

 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/sched/signal.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 <linux/uaccess.h>
 #include <asm/irq.h>
 #include <asm/mach-types.h>

 #define __NWBUTTON_C		/* Tell the header file who we are */
 #include "nwbutton.h"

 static void button_sequence_finished(struct timer_list *unused);

 static int button_press_count;		/* The count of button presses */
 /* Times for the end of a sequence */
 static DEFINE_TIMER(button_timer, button_sequence_finished);
 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;			/* 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;		/* 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.
  *
  * FIXME: Has anyone spotted any locking functions int his code recently ??
  */

 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 necessarily 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(struct timer_list *unused)
 {
 	if (IS_ENABLED(CONFIG_NWBUTTON_REBOOT) &&
 	    button_press_count == reboot_count)
 		kill_cad_pid(SIGINT, 1);	/* Ask init to reboot us */
 	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 irqreturn_t button_handler (int irq, void *dev_id)
 {
 	button_press_count++;
 	mod_timer(&button_timer, jiffies + bdelay);

 	return IRQ_HANDLED;
 }

 /*
  * 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 __user *buffer,
 			size_t count, loff_t *ppos)
 {
 	DEFINE_WAIT(wait);
 	prepare_to_wait(&button_wait_queue, &wait, TASK_INTERRUPTIBLE);
 	schedule();
 	finish_wait(&button_wait_queue, &wait);
 	return (copy_to_user (buffer, &button_output_buffer, bcount))
 		 ? -EFAULT : bcount;
 }

 /*
  * 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 const struct file_operations button_fops = {
 	.owner		= THIS_MODULE,
 	.read		= button_read,
 	.llseek		= noop_llseek,
 };

 /*
  * 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, 0,
 			"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);
 }


 MODULE_AUTHOR("Alex Holden");
 MODULE_DESCRIPTION("NetWinder button driver");
 MODULE_LICENSE("GPL");

 module_init(nwbutton_init);
 module_exit(nwbutton_exit);
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* NetWinder Button Driver-
	* Copyright (C) Alex Holden <alex@linuxhacker.org> 1998, 1999.
	*
	*/

	#include <linux/module.h>
	#include <linux/kernel.h>
	#include <linux/sched/signal.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 <linux/uaccess.h>
	#include <asm/irq.h>
	#include <asm/mach-types.h>

	#define __NWBUTTON_C /* Tell the header file who we are */
	#include "nwbutton.h"

	static void button_sequence_finished(struct timer_list *unused);

	static int button_press_count; /* The count of button presses */
	/* Times for the end of a sequence */
	static DEFINE_TIMER(button_timer, button_sequence_finished);
	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; /* 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; /* 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.
	*
	* FIXME: Has anyone spotted any locking functions int his code recently ??
	*/

	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 necessarily 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(struct timer_list *unused)
	{
	if (IS_ENABLED(CONFIG_NWBUTTON_REBOOT) &&
	button_press_count == reboot_count)
	kill_cad_pid(SIGINT, 1); /* Ask init to reboot us */
	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 irqreturn_t button_handler (int irq, void *dev_id)
	{
	button_press_count++;
	mod_timer(&button_timer, jiffies + bdelay);

	return IRQ_HANDLED;
	}

	/*
	* 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 __user buffer,
	size_t count, loff_t *ppos)
	{
	DEFINE_WAIT(wait);
	prepare_to_wait(&button_wait_queue, &wait, TASK_INTERRUPTIBLE);
	schedule();
	finish_wait(&button_wait_queue, &wait);
	return (copy_to_user (buffer, &button_output_buffer, bcount))
	? -EFAULT : bcount;
	}

	/*
	* 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 const struct file_operations button_fops = {
	.owner = THIS_MODULE,
	.read = button_read,
	.llseek = noop_llseek,
	};

	/*
	* 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, 0,
	"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);
	}


	MODULE_AUTHOR("Alex Holden");
	MODULE_DESCRIPTION("NetWinder button driver");
	MODULE_LICENSE("GPL");

	module_init(nwbutton_init);
	module_exit(nwbutton_exit);