[PATCH] tty: remove platform_sysrq_reset_seq

[PATCH] tty: remove platform_sysrq_reset_seq

[Arnd Bergmann]

The platform_sysrq_reset_seq code was intended as a way for an embedded
platform to provide its own sysrq sequence at compile time. After over
two years, nobody has started using it in an upstream kernel, and
the platforms that were interested in it have moved on to devicetree,
which can be used to configure the sequence without requiring kernel
changes. The method is also incompatible with the way that most
architectures build support for multiple platforms into a single
kernel.

Now the code is producing warnings when built with gcc-5.1:

drivers/tty/sysrq.c: In function 'sysrq_init':
drivers/tty/sysrq.c:959:33: warning: array subscript is above array bounds [-Warray-bounds]
   key = platform_sysrq_reset_seq[i];

We could fix this, but it seems unlikely that it will ever be used,
so let's just remove the code instead. We still have the option to
pass the sequence either in DT, using the kernel command line,
or using the /sys/module/sysrq/parameters/reset_seq file.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 154b7a489a ("Input: sysrq - allow specifying alternate reset sequence")

diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
index 8ba52e56bb8b..9c5395db6a57 100644
--- a/drivers/tty/sysrq.c
+++ b/drivers/tty/sysrq.c
@@ -55,8 +55,7 @@
 static int __read_mostly sysrq_enabled = CONFIG_MAGIC_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 int sysrq_reset_downtime_ms;
 
 static bool sysrq_on(void)
 {
@@ -950,23 +949,8 @@ static bool sysrq_handler_registered;
 
 static inline void sysrq_register_handler(void)
 {
-	unsigned short key;
 	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)
-			break;
 
-		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);

Re: [PATCH] tty: remove platform_sysrq_reset_seq

[Dmitry Torokhov]

On Thu, May 21, 2015 at 11:11:28AM +0200, Arnd Bergmann wrote:
> The platform_sysrq_reset_seq code was intended as a way for an embedded
> platform to provide its own sysrq sequence at compile time. After over
> two years, nobody has started using it in an upstream kernel, and
> the platforms that were interested in it have moved on to devicetree,
> which can be used to configure the sequence without requiring kernel
> changes. The method is also incompatible with the way that most
> architectures build support for multiple platforms into a single
> kernel.
> 
> Now the code is producing warnings when built with gcc-5.1:
> 
> drivers/tty/sysrq.c: In function 'sysrq_init':
> drivers/tty/sysrq.c:959:33: warning: array subscript is above array bounds [-Warray-bounds]
>    key = platform_sysrq_reset_seq[i];
> 
> We could fix this, but it seems unlikely that it will ever be used,
> so let's just remove the code instead. We still have the option to
> pass the sequence either in DT, using the kernel command line,
> or using the /sys/module/sysrq/parameters/reset_seq file.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Fixes: 154b7a489a ("Input: sysrq - allow specifying alternate reset sequence")

Mathieu, are you OK with dropping this?

> 
> diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
> index 8ba52e56bb8b..9c5395db6a57 100644
> --- a/drivers/tty/sysrq.c
> +++ b/drivers/tty/sysrq.c
> @@ -55,8 +55,7 @@
>  static int __read_mostly sysrq_enabled = CONFIG_MAGIC_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 int sysrq_reset_downtime_ms;
>  
>  static bool sysrq_on(void)
>  {
> @@ -950,23 +949,8 @@ static bool sysrq_handler_registered;
>  
>  static inline void sysrq_register_handler(void)
>  {
> -	unsigned short key;
>  	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)
> -			break;
>  
> -		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);
> 

-- 
Dmitry

Re: [PATCH] tty: remove platform_sysrq_reset_seq

[Arnd Bergmann]

On Thursday 21 May 2015 11:11:28 Arnd Bergmann wrote:
> diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
> index 8ba52e56bb8b..9c5395db6a57 100644
> --- a/drivers/tty/sysrq.c
> +++ b/drivers/tty/sysrq.c
> @@ -55,8 +55,7 @@
>  static int __read_mostly sysrq_enabled = CONFIG_MAGIC_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 int sysrq_reset_downtime_ms;
>  
>  static bool sysrq_on(void)
>  {
> 

It turns out that the variable is now potentially unused, and we get a warning
when CONFIG_INPUT is disabled. I'll send a fixed v2 of this patch.

	Arnd