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247 lines
7.9 KiB
247 lines
7.9 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* NetWinder Button Driver- |
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* Copyright (C) Alex Holden <[email protected]> 1998, 1999. |
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* |
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*/ |
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#include <linux/module.h> |
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#include <linux/kernel.h> |
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#include <linux/sched/signal.h> |
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#include <linux/interrupt.h> |
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#include <linux/time.h> |
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#include <linux/timer.h> |
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#include <linux/fs.h> |
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#include <linux/miscdevice.h> |
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#include <linux/string.h> |
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#include <linux/errno.h> |
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#include <linux/init.h> |
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#include <linux/uaccess.h> |
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#include <asm/irq.h> |
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#include <asm/mach-types.h> |
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#define __NWBUTTON_C /* Tell the header file who we are */ |
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#include "nwbutton.h" |
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static void button_sequence_finished(struct timer_list *unused); |
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static int button_press_count; /* The count of button presses */ |
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/* Times for the end of a sequence */ |
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static DEFINE_TIMER(button_timer, button_sequence_finished); |
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static DECLARE_WAIT_QUEUE_HEAD(button_wait_queue); /* Used for blocking read */ |
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static char button_output_buffer[32]; /* Stores data to write out of device */ |
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static int bcount; /* The number of bytes in the buffer */ |
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static int bdelay = BUTTON_DELAY; /* The delay, in jiffies */ |
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static struct button_callback button_callback_list[32]; /* The callback list */ |
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static int callback_count; /* The number of callbacks registered */ |
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static int reboot_count = NUM_PRESSES_REBOOT; /* Number of presses to reboot */ |
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/* |
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* This function is called by other drivers to register a callback function |
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* to be called when a particular number of button presses occurs. |
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* The callback list is a static array of 32 entries (I somehow doubt many |
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* people are ever going to want to register more than 32 different actions |
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* to be performed by the kernel on different numbers of button presses ;). |
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* However, if an attempt to register a 33rd entry (perhaps a stuck loop |
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* somewhere registering the same entry over and over?) it will fail to |
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* do so and return -ENOMEM. If an attempt is made to register a null pointer, |
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* it will fail to do so and return -EINVAL. |
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* Because callbacks can be unregistered at random the list can become |
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* fragmented, so we need to search through the list until we find the first |
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* free entry. |
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* |
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* FIXME: Has anyone spotted any locking functions int his code recently ?? |
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*/ |
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int button_add_callback (void (*callback) (void), int count) |
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{ |
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int lp = 0; |
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if (callback_count == 32) { |
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return -ENOMEM; |
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} |
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if (!callback) { |
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return -EINVAL; |
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} |
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callback_count++; |
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for (; (button_callback_list [lp].callback); lp++); |
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button_callback_list [lp].callback = callback; |
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button_callback_list [lp].count = count; |
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return 0; |
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} |
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/* |
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* This function is called by other drivers to deregister a callback function. |
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* If you attempt to unregister a callback which does not exist, it will fail |
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* with -EINVAL. If there is more than one entry with the same address, |
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* because it searches the list from end to beginning, it will unregister the |
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* last one to be registered first (FILO- First In Last Out). |
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* Note that this is not necessarily true if the entries are not submitted |
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* at the same time, because another driver could have unregistered a callback |
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* between the submissions creating a gap earlier in the list, which would |
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* be filled first at submission time. |
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*/ |
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int button_del_callback (void (*callback) (void)) |
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{ |
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int lp = 31; |
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if (!callback) { |
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return -EINVAL; |
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} |
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while (lp >= 0) { |
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if ((button_callback_list [lp].callback) == callback) { |
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button_callback_list [lp].callback = NULL; |
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button_callback_list [lp].count = 0; |
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callback_count--; |
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return 0; |
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} |
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lp--; |
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} |
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return -EINVAL; |
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} |
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/* |
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* This function is called by button_sequence_finished to search through the |
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* list of callback functions, and call any of them whose count argument |
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* matches the current count of button presses. It starts at the beginning |
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* of the list and works up to the end. It will refuse to follow a null |
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* pointer (which should never happen anyway). |
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*/ |
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static void button_consume_callbacks (int bpcount) |
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{ |
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int lp = 0; |
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for (; lp <= 31; lp++) { |
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if ((button_callback_list [lp].count) == bpcount) { |
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if (button_callback_list [lp].callback) { |
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button_callback_list[lp].callback(); |
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} |
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} |
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} |
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} |
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/* |
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* This function is called when the button_timer times out. |
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* ie. When you don't press the button for bdelay jiffies, this is taken to |
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* mean you have ended the sequence of key presses, and this function is |
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* called to wind things up (write the press_count out to /dev/button, call |
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* any matching registered function callbacks, initiate reboot, etc.). |
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*/ |
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static void button_sequence_finished(struct timer_list *unused) |
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{ |
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if (IS_ENABLED(CONFIG_NWBUTTON_REBOOT) && |
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button_press_count == reboot_count) |
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kill_cad_pid(SIGINT, 1); /* Ask init to reboot us */ |
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button_consume_callbacks (button_press_count); |
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bcount = sprintf (button_output_buffer, "%d\n", button_press_count); |
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button_press_count = 0; /* Reset the button press counter */ |
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wake_up_interruptible (&button_wait_queue); |
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} |
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/* |
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* This handler is called when the orange button is pressed (GPIO 10 of the |
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* SuperIO chip, which maps to logical IRQ 26). If the press_count is 0, |
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* this is the first press, so it starts a timer and increments the counter. |
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* If it is higher than 0, it deletes the old timer, starts a new one, and |
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* increments the counter. |
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*/ |
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static irqreturn_t button_handler (int irq, void *dev_id) |
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{ |
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button_press_count++; |
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mod_timer(&button_timer, jiffies + bdelay); |
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return IRQ_HANDLED; |
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} |
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/* |
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* This function is called when a user space program attempts to read |
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* /dev/nwbutton. It puts the device to sleep on the wait queue until |
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* button_sequence_finished writes some data to the buffer and flushes |
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* the queue, at which point it writes the data out to the device and |
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* returns the number of characters it has written. This function is |
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* reentrant, so that many processes can be attempting to read from the |
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* device at any one time. |
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*/ |
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static int button_read (struct file *filp, char __user *buffer, |
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size_t count, loff_t *ppos) |
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{ |
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DEFINE_WAIT(wait); |
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prepare_to_wait(&button_wait_queue, &wait, TASK_INTERRUPTIBLE); |
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schedule(); |
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finish_wait(&button_wait_queue, &wait); |
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return (copy_to_user (buffer, &button_output_buffer, bcount)) |
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? -EFAULT : bcount; |
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} |
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/* |
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* This structure is the file operations structure, which specifies what |
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* callbacks functions the kernel should call when a user mode process |
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* attempts to perform these operations on the device. |
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*/ |
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static const struct file_operations button_fops = { |
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.owner = THIS_MODULE, |
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.read = button_read, |
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.llseek = noop_llseek, |
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}; |
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/* |
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* This structure is the misc device structure, which specifies the minor |
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* device number (158 in this case), the name of the device (for /proc/misc), |
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* and the address of the above file operations structure. |
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*/ |
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static struct miscdevice button_misc_device = { |
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BUTTON_MINOR, |
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"nwbutton", |
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&button_fops, |
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}; |
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/* |
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* This function is called to initialise the driver, either from misc.c at |
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* bootup if the driver is compiled into the kernel, or from init_module |
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* below at module insert time. It attempts to register the device node |
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* and the IRQ and fails with a warning message if either fails, though |
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* neither ever should because the device number and IRQ are unique to |
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* this driver. |
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*/ |
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static int __init nwbutton_init(void) |
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{ |
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if (!machine_is_netwinder()) |
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return -ENODEV; |
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printk (KERN_INFO "NetWinder Button Driver Version %s (C) Alex Holden " |
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"<[email protected]> 1998.\n", VERSION); |
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if (misc_register (&button_misc_device)) { |
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printk (KERN_WARNING "nwbutton: Couldn't register device 10, " |
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"%d.\n", BUTTON_MINOR); |
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return -EBUSY; |
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} |
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if (request_irq (IRQ_NETWINDER_BUTTON, button_handler, 0, |
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"nwbutton", NULL)) { |
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printk (KERN_WARNING "nwbutton: IRQ %d is not free.\n", |
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IRQ_NETWINDER_BUTTON); |
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misc_deregister (&button_misc_device); |
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return -EIO; |
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} |
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return 0; |
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} |
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static void __exit nwbutton_exit (void) |
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{ |
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free_irq (IRQ_NETWINDER_BUTTON, NULL); |
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misc_deregister (&button_misc_device); |
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} |
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MODULE_AUTHOR("Alex Holden"); |
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MODULE_LICENSE("GPL"); |
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module_init(nwbutton_init); |
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module_exit(nwbutton_exit);
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