kernel-ark/drivers/char/nwbutton.c
David Howells 7d12e780e0 IRQ: Maintain regs pointer globally rather than passing to IRQ handlers
Maintain a per-CPU global "struct pt_regs *" variable which can be used instead
of passing regs around manually through all ~1800 interrupt handlers in the
Linux kernel.

The regs pointer is used in few places, but it potentially costs both stack
space and code to pass it around.  On the FRV arch, removing the regs parameter
from all the genirq function results in a 20% speed up of the IRQ exit path
(ie: from leaving timer_interrupt() to leaving do_IRQ()).

Where appropriate, an arch may override the generic storage facility and do
something different with the variable.  On FRV, for instance, the address is
maintained in GR28 at all times inside the kernel as part of general exception
handling.

Having looked over the code, it appears that the parameter may be handed down
through up to twenty or so layers of functions.  Consider a USB character
device attached to a USB hub, attached to a USB controller that posts its
interrupts through a cascaded auxiliary interrupt controller.  A character
device driver may want to pass regs to the sysrq handler through the input
layer which adds another few layers of parameter passing.

I've build this code with allyesconfig for x86_64 and i386.  I've runtested the
main part of the code on FRV and i386, though I can't test most of the drivers.
I've also done partial conversion for powerpc and MIPS - these at least compile
with minimal configurations.

This will affect all archs.  Mostly the changes should be relatively easy.
Take do_IRQ(), store the regs pointer at the beginning, saving the old one:

	struct pt_regs *old_regs = set_irq_regs(regs);

And put the old one back at the end:

	set_irq_regs(old_regs);

Don't pass regs through to generic_handle_irq() or __do_IRQ().

In timer_interrupt(), this sort of change will be necessary:

	-	update_process_times(user_mode(regs));
	-	profile_tick(CPU_PROFILING, regs);
	+	update_process_times(user_mode(get_irq_regs()));
	+	profile_tick(CPU_PROFILING);

I'd like to move update_process_times()'s use of get_irq_regs() into itself,
except that i386, alone of the archs, uses something other than user_mode().

Some notes on the interrupt handling in the drivers:

 (*) input_dev() is now gone entirely.  The regs pointer is no longer stored in
     the input_dev struct.

 (*) finish_unlinks() in drivers/usb/host/ohci-q.c needs checking.  It does
     something different depending on whether it's been supplied with a regs
     pointer or not.

 (*) Various IRQ handler function pointers have been moved to type
     irq_handler_t.

Signed-Off-By: David Howells <dhowells@redhat.com>
(cherry picked from 1b16e7ac850969f38b375e511e3fa2f474a33867 commit)
2006-10-05 15:10:12 +01:00

247 lines
7.9 KiB
C

/*
* 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 int button_press_count; /* The count of button presses */
static struct timer_list button_timer; /* Times for the end of a sequence */
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 neccessarily 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)
{
if (button_press_count) {
del_timer (&button_timer);
}
button_press_count++;
init_timer (&button_timer);
button_timer.function = button_sequence_finished;
button_timer.expires = (jiffies + bdelay);
add_timer (&button_timer);
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)
{
interruptible_sleep_on (&button_wait_queue);
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,
};
/*
* 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, IRQF_DISABLED,
"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);