diff options
Diffstat (limited to 'drivers/char/nwbutton.c')
| -rw-r--r-- | drivers/char/nwbutton.c | 246 |
1 files changed, 246 insertions, 0 deletions
diff --git a/drivers/char/nwbutton.c b/drivers/char/nwbutton.c new file mode 100644 index 000000000..a7113b782 --- /dev/null +++ b/drivers/char/nwbutton.c @@ -0,0 +1,246 @@ +/* + * 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_LICENSE("GPL"); + +module_init(nwbutton_init); +module_exit(nwbutton_exit); |