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Commit 4c076eb0 authored by Mathieu J. Poirier's avatar Mathieu J. Poirier Committed by Dmitry Torokhov
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Input: sysrq - DT binding for key sequence 



Adding a simple device tree binding for the specification of key
sequences. Definition of the keys found in the sequence are located in
'include/uapi/linux/input.h'.

For the sysrq driver, holding the sequence of keys down for a specific
amount of time will reset the system.

Signed-off-by: default avatarMathieu Poirier <mathieu.poirier@linaro.org>
Acked-by: default avatarGrant Likely <grant.likely@linaro.org>
Signed-off-by: default avatarDmitry Torokhov <dmitry.torokhov@gmail.com>
parent 401d7d10

Documentation/devicetree/bindings/input/input-reset.txt

0 → 100644
+33 −0
Original line number Diff line number Diff line 
Input: sysrq reset sequence



A simple binding to represent a set of keys as described in

include/uapi/linux/input.h. This is to communicate a sequence of keys to the

sysrq driver. Upon holding the keys for a specified amount of time (if

specified) the system is sync'ed and reset.



Key sequences are global to the system but all the keys in a set must be coming

from the same input device.



The /chosen node should contain a 'linux,sysrq-reset-seq' child node to define

a set of keys.



Required property:

sysrq-reset-seq: array of Linux keycodes, one keycode per cell.



Optional property:

timeout-ms: duration keys must be pressed together in milliseconds before

generating a sysrq. If omitted the system is rebooted immediately when a valid

sequence has been recognized.



Example:



 chosen {

                linux,sysrq-reset-seq {

                        keyset = <0x03

                                  0x04

                                  0x0a>;

                        timeout-ms = <3000>;

                };

         };



Would represent KEY_2, KEY_3 and KEY_9.

drivers/tty/sysrq.c

+42 −0
Original line number Diff line number Diff line
@@ -45,6 +45,7 @@ 
#include <linux/moduleparam.h>

#include <linux/jiffies.h>

#include <linux/syscalls.h>

#include <linux/of.h>



#include <asm/ptrace.h>

#include <asm/irq_regs.h>
@@ -681,6 +682,40 @@ static void sysrq_detect_reset_sequence(struct sysrq_state *state, 
	}

}



#ifdef CONFIG_OF

static void sysrq_of_get_keyreset_config(void)

{

	u32 key;

	struct device_node *np;

	struct property *prop;

	const __be32 *p;



	np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");

	if (!np) {

		pr_debug("No sysrq node found");

		return;

	}



	/* Reset in case a __weak definition was present */

	sysrq_reset_seq_len = 0;



	of_property_for_each_u32(np, "keyset", prop, p, key) {

		if (key == KEY_RESERVED || key > KEY_MAX ||

		    sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)

			break;



		sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;

	}



	/* Get reset timeout if any. */

	of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);

}

#else

static void sysrq_of_get_keyreset_config(void)

{

}

#endif



static void sysrq_reinject_alt_sysrq(struct work_struct *work)

{

	struct sysrq_state *sysrq =
@@ -914,6 +949,7 @@ static inline void sysrq_register_handler(void) 
	int error;

	int i;



	/* First check if a __weak interface was instantiated. */

	for (i = 0; i < ARRAY_SIZE(sysrq_reset_seq); i++) {

		key = platform_sysrq_reset_seq[i];

		if (key == KEY_RESERVED || key > KEY_MAX)
@@ -922,6 +958,12 @@ static inline void sysrq_register_handler(void) 
		sysrq_reset_seq[sysrq_reset_seq_len++] = key;

	}



	/*

	 * DT configuration takes precedence over anything that would

	 * have been defined via the __weak interface.

	 */

	sysrq_of_get_keyreset_config();



	error = input_register_handler(&sysrq_handler);

	if (error)

		pr_err("Failed to register input handler, error %d", error);