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Commit 39030786 authored by Mathieu J. Poirier's avatar Mathieu J. Poirier Committed by Dmitry Torokhov
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Input: sysrq - supplement reset sequence with timeout functionality 



Some devices have too few buttons, which it makes it hard to have
a reset combo that won't trigger automatically.  As such a
timeout functionality that requires the combination to be held for
a given amount of time before triggering is introduced.

If a key combo is recognized and held for a 'timeout' amount of time,
the system triggers a reset.  If the timeout value is omitted the
driver simply ignores the functionality.

Signed-off-by: default avatarMathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: default avatarDmitry Torokhov <dmitry.torokhov@gmail.com>
parent e10af9e7

drivers/tty/sysrq.c

+40 −13
Original line number Diff line number Diff line
@@ -43,6 +43,7 @@ 
#include <linux/input.h>

#include <linux/uaccess.h>

#include <linux/moduleparam.h>

#include <linux/jiffies.h>



#include <asm/ptrace.h>

#include <asm/irq_regs.h>
@@ -51,6 +52,9 @@ 
static int __read_mostly sysrq_enabled = SYSRQ_DEFAULT_ENABLE;

static bool __read_mostly sysrq_always_enabled;



unsigned short platform_sysrq_reset_seq[] __weak = { KEY_RESERVED };

int sysrq_reset_downtime_ms __weak;



static bool sysrq_on(void)

{

	return sysrq_enabled || sysrq_always_enabled;
@@ -586,6 +590,7 @@ struct sysrq_state { 
	int reset_seq_len;

	int reset_seq_cnt;

	int reset_seq_version;

	struct timer_list keyreset_timer;

};



#define SYSRQ_KEY_RESET_MAX	20 /* Should be plenty */
@@ -619,29 +624,51 @@ static void sysrq_parse_reset_sequence(struct sysrq_state *state) 
	state->reset_seq_version = sysrq_reset_seq_version;

}



static bool sysrq_detect_reset_sequence(struct sysrq_state *state,

static void sysrq_do_reset(unsigned long dummy)

{

	__handle_sysrq(sysrq_xlate[KEY_B], false);

}



static void sysrq_handle_reset_request(struct sysrq_state *state)

{

	if (sysrq_reset_downtime_ms)

		mod_timer(&state->keyreset_timer,

			jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));

	else

		sysrq_do_reset(0);

}



static void sysrq_detect_reset_sequence(struct sysrq_state *state,

					unsigned int code, int value)

{

	if (!test_bit(code, state->reset_keybit)) {

		/*

		 * Pressing any key _not_ in reset sequence cancels

		 * the reset sequence.

		 * the reset sequence.  Also cancelling the timer in

		 * case additional keys were pressed after a reset

		 * has been requested.

		 */

		if (value && state->reset_seq_cnt)

		if (value && state->reset_seq_cnt) {

			state->reset_canceled = true;

			del_timer(&state->keyreset_timer);

		}

	} else if (value == 0) {

		/* key release */

		/*

		 * Key release - all keys in the reset sequence need

		 * to be pressed and held for the reset timeout

		 * to hold.

		 */

		del_timer(&state->keyreset_timer);



		if (--state->reset_seq_cnt == 0)

			state->reset_canceled = false;

	} else if (value == 1) {

		/* key press, not autorepeat */

		if (++state->reset_seq_cnt == state->reset_seq_len &&

		    !state->reset_canceled) {

			return true;

			sysrq_handle_reset_request(state);

		}

	}



	return false;

}



static void sysrq_reinject_alt_sysrq(struct work_struct *work)
@@ -748,10 +775,8 @@ static bool sysrq_handle_keypress(struct sysrq_state *sysrq, 
		if (was_active)

			schedule_work(&sysrq->reinject_work);



		if (sysrq_detect_reset_sequence(sysrq, code, value)) {

			/* Force emergency reboot */

			__handle_sysrq(sysrq_xlate[KEY_B], false);

		}

		/* Check for reset sequence */

		sysrq_detect_reset_sequence(sysrq, code, value);



	} else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {

		/*
@@ -812,6 +837,7 @@ static int sysrq_connect(struct input_handler *handler, 
	sysrq->handle.handler = handler;

	sysrq->handle.name = "sysrq";

	sysrq->handle.private = sysrq;

	setup_timer(&sysrq->keyreset_timer, sysrq_do_reset, 0);



	error = input_register_handle(&sysrq->handle);

	if (error) {
@@ -841,6 +867,7 @@ static void sysrq_disconnect(struct input_handle *handle) 


	input_close_device(handle);

	cancel_work_sync(&sysrq->reinject_work);

	del_timer_sync(&sysrq->keyreset_timer);

	input_unregister_handle(handle);

	kfree(sysrq);

}
@@ -870,8 +897,6 @@ static struct input_handler sysrq_handler = { 


static bool sysrq_handler_registered;



unsigned short platform_sysrq_reset_seq[] __weak = { KEY_RESERVED };



static inline void sysrq_register_handler(void)

{

	unsigned short key;
@@ -931,6 +956,8 @@ static struct kernel_param_ops param_ops_sysrq_reset_seq = { 
module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,

			 &sysrq_reset_seq_len, 0644);



module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);



#else



static inline void sysrq_register_handler(void)