--- /dev/null
+/*
+ * NetWinder Button Driver-
+ * Copyright (C) Alex Holden <alex@linuxhacker.org> 1998, 1999.
+ *
+ */
+
+#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>
+#include <asm/mach-types.h>
+
+#define __NWBUTTON_C /* Tell the header file who we are */
+#include "nwbutton.h"
+
+static void button_sequence_finished (unsigned long parameters);
+
+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, 0, 0);
+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 (unsigned long parameters)
+{
+#ifdef CONFIG_NWBUTTON_REBOOT /* Reboot using button is enabled */
+ if (button_press_count == reboot_count)
+ kill_cad_pid(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 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);
Code Review / kvmfornfv.git / blobdiff