diff mbox series

tty/sysrq: Add alternative SysRq key

Message ID 20200619162819.715-1-andrzej.p@collabora.com (mailing list archive)
State New, archived
Headers show
Series tty/sysrq: Add alternative SysRq key | expand

Commit Message

Andrzej Pietrasiewicz June 19, 2020, 4:28 p.m. UTC 
There exist machines which don't have SysRq key at all, e.g. chromebooks.

This patch allows configuring an alternative key to act as SysRq. Devices
which declare KEY_SYSRQ in their 'keybit' bitmap continue using KEY_SYSRQ,
but other devices use the alternative SysRq key instead, by default F10.
Which key is actually used can be modified with sysrq's module parameter.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
---
 drivers/tty/sysrq.c | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)


base-commit: 3d77e6a8804abcc0504c904bd6e5cdf3a5cf8162

Comments

Pavel Machek June 21, 2020, 9:21 p.m. UTC | #1 
Hi!

> There exist machines which don't have SysRq key at all, e.g. chromebooks.
> 
> This patch allows configuring an alternative key to act as SysRq. Devices
> which declare KEY_SYSRQ in their 'keybit' bitmap continue using KEY_SYSRQ,
> but other devices use the alternative SysRq key instead, by default F10.
> Which key is actually used can be modified with sysrq's module parameter.
> 
> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>

So... SysRq was selected because you are not going to press
Alt-Printscreen-X by default.

I'm not sure if F10 is similar level of "impossible to press by
mistake", altrough holding up F10-B is likely not too common. Maybe it
should be some combination for chromebooks?
Leftshift-rightshift-F10-key? Ctrl-alt-del-key? :-).

Best regards,
								Pavel
Jiri Slaby June 22, 2020, 6:24 a.m. UTC | #2 
On 19. 06. 20, 18:28, Andrzej Pietrasiewicz wrote:
> There exist machines which don't have SysRq key at all, e.g. chromebooks.
> 
> This patch allows configuring an alternative key to act as SysRq. Devices
> which declare KEY_SYSRQ in their 'keybit' bitmap continue using KEY_SYSRQ,
> but other devices use the alternative SysRq key instead, by default F10.
> Which key is actually used can be modified with sysrq's module parameter.
> 
> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> ---
>  drivers/tty/sysrq.c | 28 +++++++++++++++++++++++++---
>  1 file changed, 25 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
> index 0dc3878794fd..e1d271c84746 100644
> --- a/drivers/tty/sysrq.c
> +++ b/drivers/tty/sysrq.c
> @@ -604,6 +604,7 @@ EXPORT_SYMBOL(handle_sysrq);
>  
>  #ifdef CONFIG_INPUT
>  static int sysrq_reset_downtime_ms;
> +static unsigned short alternative_sysrq_key = KEY_F10;

I would go for sysrq_alternative_key to preserve the namespace naming.

> @@ -825,11 +828,15 @@ static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
>  		 * triggering print screen function.
>  		 */
>  		if (sysrq->active)
> -			clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
> +			clear_bit(sysrq->sysrq_key, sysrq->handle.dev->key);
>  
>  		break;
>  
>  	default:
> +		/* handle non-default sysrq key */
> +		if (code == sysrq->sysrq_key)
> +			goto key_sysrq;
> +
>  		if (sysrq->active && value && value != 2) {
>  			sysrq->need_reinject = false;
>  			__handle_sysrq(sysrq_xlate[code], true);
> @@ -924,6 +931,14 @@ static int sysrq_connect(struct input_handler *handler,
>  	sysrq->handle.private = sysrq;
>  	timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
>  
> +	if (test_bit(KEY_SYSRQ, dev->keybit)) {
> +		sysrq->sysrq_key = KEY_SYSRQ;
> +		pr_info("%s: using default sysrq key [%x]\n", dev->name, KEY_SYSRQ);
> +	} else {
> +		sysrq->sysrq_key = alternative_sysrq_key;
> +		pr_info("%s: Using alternative sysrq key: [%x]\n", dev->name, sysrq->sysrq_key);

Capital U, lowercase u above. Do we want to print the info in the
default case, actually?

> +	}
> +
>  	error = input_register_handle(&sysrq->handle);
>  	if (error) {
>  		pr_err("Failed to register input sysrq handler, error %d\n",
> @@ -1032,6 +1047,13 @@ module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
>  
>  module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
>  
> +module_param(alternative_sysrq_key, ushort, 0644);
> +MODULE_PARM_DESC(alternative_sysrq_key,
> +	"Alternative SysRq key for input devices that don't have SysRq key. F10 by default.\n"

If you line-break here, I suggest adding a \t or two to the beginning of
the following lines:

> +	"Example\n"
> +	"Using F9 as SysRq:\n"
> +	"sysrq.alternative_sysrq_key=0x43\n");

The last \n is superfluous, there would be an empty line.

Looking at emulate_raw in drivers/tty/vt/keyboard.c, you seem you need
to update that one as well. Otherwise raw keyboard mode won't send sysrq
sequence, when you press it, right?

thanks,
Andrzej Pietrasiewicz June 26, 2020, 11:07 a.m. UTC | #3 
Hi Pavel,

W dniu 21.06.2020 o 23:21, Pavel Machek pisze:
> Hi!
> 
>> There exist machines which don't have SysRq key at all, e.g. chromebooks.
>>
>> This patch allows configuring an alternative key to act as SysRq. Devices
>> which declare KEY_SYSRQ in their 'keybit' bitmap continue using KEY_SYSRQ,
>> but other devices use the alternative SysRq key instead, by default F10.
>> Which key is actually used can be modified with sysrq's module parameter.
>>
>> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> 
> So... SysRq was selected because you are not going to press
> Alt-Printscreen-X by default.

This patch does not change the Alt-PrintScreen/SysRq-something sequence.
What it does instead is making the 'PrintScreen/SysRq' component of the
sequence configurable for input devices which don't declare KEY_SYSRQ in
their 'keybit' bitmap, so the sequence becomes:

Alt-<alternative sysrq key>-something

If the alternative sysrq key is used (i.e. the input device in question
does not declare KEY_SYSRQ), it is F10 by default and _that_ can be changed
with the module parameter.

To summarize:

- devices which do declare KEY_SYSRQ must use Alt-PrintScreen/SysRq-something
- devices which don't declare KEY_SYSRQ must use Alt-F10-something, but F10
can be changed with a module parameter to something else

Regards,

Andrzej
Andrzej Pietrasiewicz June 26, 2020, 11:51 a.m. UTC | #4 
Hi Jiri,

W dniu 22.06.2020 o 08:24, Jiri Slaby pisze:
> On 19. 06. 20, 18:28, Andrzej Pietrasiewicz wrote:
>> There exist machines which don't have SysRq key at all, e.g. chromebooks.
>>
>> This patch allows configuring an alternative key to act as SysRq. Devices
>> which declare KEY_SYSRQ in their 'keybit' bitmap continue using KEY_SYSRQ,
>> but other devices use the alternative SysRq key instead, by default F10.
>> Which key is actually used can be modified with sysrq's module parameter.
>>
>> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
>> ---
>>   drivers/tty/sysrq.c | 28 +++++++++++++++++++++++++---
>>   1 file changed, 25 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
>> index 0dc3878794fd..e1d271c84746 100644
>> --- a/drivers/tty/sysrq.c
>> +++ b/drivers/tty/sysrq.c
>> @@ -604,6 +604,7 @@ EXPORT_SYMBOL(handle_sysrq);
>>   
>>   #ifdef CONFIG_INPUT
>>   static int sysrq_reset_downtime_ms;
>> +static unsigned short alternative_sysrq_key = KEY_F10;
> 
> I would go for sysrq_alternative_key to preserve the namespace naming.
> 
>> @@ -825,11 +828,15 @@ static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
>>   		 * triggering print screen function.
>>   		 */
>>   		if (sysrq->active)
>> -			clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
>> +			clear_bit(sysrq->sysrq_key, sysrq->handle.dev->key);
>>   
>>   		break;
>>   
>>   	default:
>> +		/* handle non-default sysrq key */
>> +		if (code == sysrq->sysrq_key)
>> +			goto key_sysrq;
>> +
>>   		if (sysrq->active && value && value != 2) {
>>   			sysrq->need_reinject = false;
>>   			__handle_sysrq(sysrq_xlate[code], true);
>> @@ -924,6 +931,14 @@ static int sysrq_connect(struct input_handler *handler,
>>   	sysrq->handle.private = sysrq;
>>   	timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
>>   
>> +	if (test_bit(KEY_SYSRQ, dev->keybit)) {
>> +		sysrq->sysrq_key = KEY_SYSRQ;
>> +		pr_info("%s: using default sysrq key [%x]\n", dev->name, KEY_SYSRQ);
>> +	} else {
>> +		sysrq->sysrq_key = alternative_sysrq_key;
>> +		pr_info("%s: Using alternative sysrq key: [%x]\n", dev->name, sysrq->sysrq_key);
> 
> Capital U, lowercase u above. Do we want to print the info in the
> default case, actually?
> 
>> +	}
>> +
>>   	error = input_register_handle(&sysrq->handle);
>>   	if (error) {
>>   		pr_err("Failed to register input sysrq handler, error %d\n",
>> @@ -1032,6 +1047,13 @@ module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
>>   
>>   module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
>>   
>> +module_param(alternative_sysrq_key, ushort, 0644);
>> +MODULE_PARM_DESC(alternative_sysrq_key,
>> +	"Alternative SysRq key for input devices that don't have SysRq key. F10 by default.\n"
> 
> If you line-break here, I suggest adding a \t or two to the beginning of
> the following lines:
> 
>> +	"Example\n"
>> +	"Using F9 as SysRq:\n"
>> +	"sysrq.alternative_sysrq_key=0x43\n");
> 
> The last \n is superfluous, there would be an empty line.
> 
> Looking at emulate_raw in drivers/tty/vt/keyboard.c, you seem you need
> to update that one as well. Otherwise raw keyboard mode won't send sysrq
> sequence, when you press it, right?
> 

The way I understand the input subsystem kbd_handler and sysrq_handler are
independent. The purpose of the former is to provide keystrokes to the
(current) terminal, while the purpose of the latter is to execute predefined
actions when specific key combinations are pressed. What is more,
the sysrq_handler is actually a filter and when one of its actions is triggered
then the corresponding keystrokes are filtered-out.

Regards,

Andrzej
Dmitry Torokhov July 9, 2020, 5:05 a.m. UTC | #5 
Hi Andrzej,

On Fri, Jun 19, 2020 at 06:28:19PM +0200, Andrzej Pietrasiewicz wrote:
> There exist machines which don't have SysRq key at all, e.g. chromebooks.
> 
> This patch allows configuring an alternative key to act as SysRq. Devices
> which declare KEY_SYSRQ in their 'keybit' bitmap continue using KEY_SYSRQ,
> but other devices use the alternative SysRq key instead, by default F10.
> Which key is actually used can be modified with sysrq's module parameter.

I guess you will be removing KEY_SYSRQ form all Chrome OS internal AT
keyboards and external USB keyboard with Chrome OS layouts as well? Via
udev keymap? I suppose this could work... Or have a per device setting
as we allocate a separate handle for each input device attached to the
SysRq handler.

> 
> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> ---
>  drivers/tty/sysrq.c | 28 +++++++++++++++++++++++++---
>  1 file changed, 25 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
> index 0dc3878794fd..e1d271c84746 100644
> --- a/drivers/tty/sysrq.c
> +++ b/drivers/tty/sysrq.c
> @@ -604,6 +604,7 @@ EXPORT_SYMBOL(handle_sysrq);
>  
>  #ifdef CONFIG_INPUT
>  static int sysrq_reset_downtime_ms;
> +static unsigned short alternative_sysrq_key = KEY_F10;
>  
>  /* Simple translation table for the SysRq keys */
>  static const unsigned char sysrq_xlate[KEY_CNT] =
> @@ -621,6 +622,7 @@ struct sysrq_state {
>  	unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
>  	unsigned int alt;
>  	unsigned int alt_use;
> +	unsigned short sysrq_key;
>  	bool active;
>  	bool need_reinject;
>  	bool reinjecting;
> @@ -770,10 +772,10 @@ static void sysrq_reinject_alt_sysrq(struct work_struct *work)
>  
>  		/* Simulate press and release of Alt + SysRq */
>  		input_inject_event(handle, EV_KEY, alt_code, 1);
> -		input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
> +		input_inject_event(handle, EV_KEY, sysrq->sysrq_key, 1);
>  		input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
>  
> -		input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
> +		input_inject_event(handle, EV_KEY, sysrq->sysrq_key, 0);
>  		input_inject_event(handle, EV_KEY, alt_code, 0);
>  		input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
>  
> @@ -805,6 +807,7 @@ static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
>  		}
>  		break;
>  
> +key_sysrq:
>  	case KEY_SYSRQ:
>  		if (value == 1 && sysrq->alt != KEY_RESERVED) {
>  			sysrq->active = true;
> @@ -825,11 +828,15 @@ static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
>  		 * triggering print screen function.
>  		 */
>  		if (sysrq->active)
> -			clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
> +			clear_bit(sysrq->sysrq_key, sysrq->handle.dev->key);
>  
>  		break;
>  
>  	default:
> +		/* handle non-default sysrq key */
> +		if (code == sysrq->sysrq_key)
> +			goto key_sysrq;
> +
>  		if (sysrq->active && value && value != 2) {
>  			sysrq->need_reinject = false;
>  			__handle_sysrq(sysrq_xlate[code], true);
> @@ -924,6 +931,14 @@ static int sysrq_connect(struct input_handler *handler,
>  	sysrq->handle.private = sysrq;
>  	timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
>  
> +	if (test_bit(KEY_SYSRQ, dev->keybit)) {
> +		sysrq->sysrq_key = KEY_SYSRQ;
> +		pr_info("%s: using default sysrq key [%x]\n", dev->name, KEY_SYSRQ);
> +	} else {
> +		sysrq->sysrq_key = alternative_sysrq_key;
> +		pr_info("%s: Using alternative sysrq key: [%x]\n", dev->name, sysrq->sysrq_key);
> +	}

This is way too noisy IMO.

> +
>  	error = input_register_handle(&sysrq->handle);
>  	if (error) {
>  		pr_err("Failed to register input sysrq handler, error %d\n",
> @@ -1032,6 +1047,13 @@ module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
>  
>  module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
>  
> +module_param(alternative_sysrq_key, ushort, 0644);
> +MODULE_PARM_DESC(alternative_sysrq_key,
> +	"Alternative SysRq key for input devices that don't have SysRq key. F10 by default.\n"
> +	"Example\n"
> +	"Using F9 as SysRq:\n"
> +	"sysrq.alternative_sysrq_key=0x43\n");
> +
>  #else
>  
>  static inline void sysrq_register_handler(void)
> 
> base-commit: 3d77e6a8804abcc0504c904bd6e5cdf3a5cf8162
> -- 
> 2.17.1
>
Andrzej Pietrasiewicz July 9, 2020, 8:15 a.m. UTC | #6 
Hi Dmitry,

W dniu 09.07.2020 o 07:05, Dmitry Torokhov pisze:
> Hi Andrzej,
> 
> On Fri, Jun 19, 2020 at 06:28:19PM +0200, Andrzej Pietrasiewicz wrote:
>> There exist machines which don't have SysRq key at all, e.g. chromebooks.
>>
>> This patch allows configuring an alternative key to act as SysRq. Devices
>> which declare KEY_SYSRQ in their 'keybit' bitmap continue using KEY_SYSRQ,
>> but other devices use the alternative SysRq key instead, by default F10.
>> Which key is actually used can be modified with sysrq's module parameter.
> 
> I guess you will be removing KEY_SYSRQ form all Chrome OS internal AT
> keyboards and external USB keyboard with Chrome OS layouts as well? Via
> udev keymap? I suppose this could work... Or have a per device setting
> as we allocate a separate handle for each input device attached to the
> SysRq handler.
> 

To me it makes most sense to have the decision taken per each input
device - if it is capable of providing KEY_SYSRQ, then it is used,
otherwise the alternative is taken.

The question is how to provide this information at ->connect() time.

Ideally chromebook's keyboard should be modelled in such a way that
it reflects reality. And the reality is that chromebooks probably
declare they use full AT PS/2 keyboard even though they have less keys.

It is unclear to me whether it makes sense to struggle to better
reflect actual keys repertoire at the kernel level. If udev's keymap
can be used, that should do. Now, are we able to guarantee that the
modification of the keyboard layout happens before the sysrq handler
is matched against the keyboard?

Andrzej

>>
>> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
>> ---
>>   drivers/tty/sysrq.c | 28 +++++++++++++++++++++++++---
>>   1 file changed, 25 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
>> index 0dc3878794fd..e1d271c84746 100644
>> --- a/drivers/tty/sysrq.c
>> +++ b/drivers/tty/sysrq.c
>> @@ -604,6 +604,7 @@ EXPORT_SYMBOL(handle_sysrq);
>>   
>>   #ifdef CONFIG_INPUT
>>   static int sysrq_reset_downtime_ms;
>> +static unsigned short alternative_sysrq_key = KEY_F10;
>>   
>>   /* Simple translation table for the SysRq keys */
>>   static const unsigned char sysrq_xlate[KEY_CNT] =
>> @@ -621,6 +622,7 @@ struct sysrq_state {
>>   	unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
>>   	unsigned int alt;
>>   	unsigned int alt_use;
>> +	unsigned short sysrq_key;
>>   	bool active;
>>   	bool need_reinject;
>>   	bool reinjecting;
>> @@ -770,10 +772,10 @@ static void sysrq_reinject_alt_sysrq(struct work_struct *work)
>>   
>>   		/* Simulate press and release of Alt + SysRq */
>>   		input_inject_event(handle, EV_KEY, alt_code, 1);
>> -		input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
>> +		input_inject_event(handle, EV_KEY, sysrq->sysrq_key, 1);
>>   		input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
>>   
>> -		input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
>> +		input_inject_event(handle, EV_KEY, sysrq->sysrq_key, 0);
>>   		input_inject_event(handle, EV_KEY, alt_code, 0);
>>   		input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
>>   
>> @@ -805,6 +807,7 @@ static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
>>   		}
>>   		break;
>>   
>> +key_sysrq:
>>   	case KEY_SYSRQ:
>>   		if (value == 1 && sysrq->alt != KEY_RESERVED) {
>>   			sysrq->active = true;
>> @@ -825,11 +828,15 @@ static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
>>   		 * triggering print screen function.
>>   		 */
>>   		if (sysrq->active)
>> -			clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
>> +			clear_bit(sysrq->sysrq_key, sysrq->handle.dev->key);
>>   
>>   		break;
>>   
>>   	default:
>> +		/* handle non-default sysrq key */
>> +		if (code == sysrq->sysrq_key)
>> +			goto key_sysrq;
>> +
>>   		if (sysrq->active && value && value != 2) {
>>   			sysrq->need_reinject = false;
>>   			__handle_sysrq(sysrq_xlate[code], true);
>> @@ -924,6 +931,14 @@ static int sysrq_connect(struct input_handler *handler,
>>   	sysrq->handle.private = sysrq;
>>   	timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
>>   
>> +	if (test_bit(KEY_SYSRQ, dev->keybit)) {
>> +		sysrq->sysrq_key = KEY_SYSRQ;
>> +		pr_info("%s: using default sysrq key [%x]\n", dev->name, KEY_SYSRQ);
>> +	} else {
>> +		sysrq->sysrq_key = alternative_sysrq_key;
>> +		pr_info("%s: Using alternative sysrq key: [%x]\n", dev->name, sysrq->sysrq_key);
>> +	}
> 
> This is way too noisy IMO.
> 
>> +
>>   	error = input_register_handle(&sysrq->handle);
>>   	if (error) {
>>   		pr_err("Failed to register input sysrq handler, error %d\n",
>> @@ -1032,6 +1047,13 @@ module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
>>   
>>   module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
>>   
>> +module_param(alternative_sysrq_key, ushort, 0644);
>> +MODULE_PARM_DESC(alternative_sysrq_key,
>> +	"Alternative SysRq key for input devices that don't have SysRq key. F10 by default.\n"
>> +	"Example\n"
>> +	"Using F9 as SysRq:\n"
>> +	"sysrq.alternative_sysrq_key=0x43\n");
>> +
>>   #else
>>   
>>   static inline void sysrq_register_handler(void)
>>
>> base-commit: 3d77e6a8804abcc0504c904bd6e5cdf3a5cf8162
>> -- 
>> 2.17.1
>>
>
diff mbox series

Patch

diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
index 0dc3878794fd..e1d271c84746 100644
--- a/drivers/tty/sysrq.c
+++ b/drivers/tty/sysrq.c
@@ -604,6 +604,7 @@  EXPORT_SYMBOL(handle_sysrq);
 
 #ifdef CONFIG_INPUT
 static int sysrq_reset_downtime_ms;
+static unsigned short alternative_sysrq_key = KEY_F10;
 
 /* Simple translation table for the SysRq keys */
 static const unsigned char sysrq_xlate[KEY_CNT] =
@@ -621,6 +622,7 @@  struct sysrq_state {
 	unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
 	unsigned int alt;
 	unsigned int alt_use;
+	unsigned short sysrq_key;
 	bool active;
 	bool need_reinject;
 	bool reinjecting;
@@ -770,10 +772,10 @@  static void sysrq_reinject_alt_sysrq(struct work_struct *work)
 
 		/* Simulate press and release of Alt + SysRq */
 		input_inject_event(handle, EV_KEY, alt_code, 1);
-		input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
+		input_inject_event(handle, EV_KEY, sysrq->sysrq_key, 1);
 		input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 
-		input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
+		input_inject_event(handle, EV_KEY, sysrq->sysrq_key, 0);
 		input_inject_event(handle, EV_KEY, alt_code, 0);
 		input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 
@@ -805,6 +807,7 @@  static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
 		}
 		break;
 
+key_sysrq:
 	case KEY_SYSRQ:
 		if (value == 1 && sysrq->alt != KEY_RESERVED) {
 			sysrq->active = true;
@@ -825,11 +828,15 @@  static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
 		 * triggering print screen function.
 		 */
 		if (sysrq->active)
-			clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
+			clear_bit(sysrq->sysrq_key, sysrq->handle.dev->key);
 
 		break;
 
 	default:
+		/* handle non-default sysrq key */
+		if (code == sysrq->sysrq_key)
+			goto key_sysrq;
+
 		if (sysrq->active && value && value != 2) {
 			sysrq->need_reinject = false;
 			__handle_sysrq(sysrq_xlate[code], true);
@@ -924,6 +931,14 @@  static int sysrq_connect(struct input_handler *handler,
 	sysrq->handle.private = sysrq;
 	timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
 
+	if (test_bit(KEY_SYSRQ, dev->keybit)) {
+		sysrq->sysrq_key = KEY_SYSRQ;
+		pr_info("%s: using default sysrq key [%x]\n", dev->name, KEY_SYSRQ);
+	} else {
+		sysrq->sysrq_key = alternative_sysrq_key;
+		pr_info("%s: Using alternative sysrq key: [%x]\n", dev->name, sysrq->sysrq_key);
+	}
+
 	error = input_register_handle(&sysrq->handle);
 	if (error) {
 		pr_err("Failed to register input sysrq handler, error %d\n",
@@ -1032,6 +1047,13 @@  module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
 
 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
 
+module_param(alternative_sysrq_key, ushort, 0644);
+MODULE_PARM_DESC(alternative_sysrq_key,
+	"Alternative SysRq key for input devices that don't have SysRq key. F10 by default.\n"
+	"Example\n"
+	"Using F9 as SysRq:\n"
+	"sysrq.alternative_sysrq_key=0x43\n");
+
 #else
 
 static inline void sysrq_register_handler(void)