// 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);
