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* [PATCH] Input: atmel_mxt_ts - Remove unnecessary byte_offset check
@ 2017-10-08 18:44 Christos Gkekas
  2017-10-08 19:41 ` Nick Dyer
  0 siblings, 1 reply; 4+ messages in thread
From: Christos Gkekas @ 2017-10-08 18:44 UTC (permalink / raw)
  To: Nick Dyer, Dmitry Torokhov, linux-input, linux-kernel; +Cc: Christos Gkekas

Variable byte_offset is unsigned so checking whether it is greater or
equal to zero is redundant.

Signed-off-by: Christos Gkekas <chris.gekas@gmail.com>
---
 drivers/input/touchscreen/atmel_mxt_ts.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/touchscreen/atmel_mxt_ts.c
index 7659bc4..baafaed 100644
--- a/drivers/input/touchscreen/atmel_mxt_ts.c
+++ b/drivers/input/touchscreen/atmel_mxt_ts.c
@@ -1356,7 +1356,7 @@ static int mxt_prepare_cfg_mem(struct mxt_data *data,
 
 			byte_offset = reg + i - cfg_start_ofs;
 
-			if (byte_offset >= 0 && byte_offset < config_mem_size) {
+			if (byte_offset < config_mem_size) {
 				*(config_mem + byte_offset) = val;
 			} else {
 				dev_err(dev, "Bad object: reg:%d, T%d, ofs=%d\n",
-- 
2.7.4

^ permalink raw reply related	[flat|nested] 4+ messages in thread
* Re: [PATCH] Input: atmel_mxt_ts - Remove unnecessary byte_offset check
  2017-10-08 18:44 [PATCH] Input: atmel_mxt_ts - Remove unnecessary byte_offset check Christos Gkekas
@ 2017-10-08 19:41 ` Nick Dyer
  2017-10-09 17:38   ` Dmitry Torokhov
  0 siblings, 1 reply; 4+ messages in thread
From: Nick Dyer @ 2017-10-08 19:41 UTC (permalink / raw)
  To: Christos Gkekas; +Cc: Dmitry Torokhov, linux-input, linux-kernel

On Sun, Oct 08, 2017 at 07:44:18PM +0100, Christos Gkekas wrote:
> Variable byte_offset is unsigned so checking whether it is greater or
> equal to zero is redundant.
> 
> Signed-off-by: Christos Gkekas <chris.gekas@gmail.com>

Yep - looks sensible to me.

Signed-off-by: Nick Dyer <nick@shmanahar.org>

> ---
>  drivers/input/touchscreen/atmel_mxt_ts.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/touchscreen/atmel_mxt_ts.c
> index 7659bc4..baafaed 100644
> --- a/drivers/input/touchscreen/atmel_mxt_ts.c
> +++ b/drivers/input/touchscreen/atmel_mxt_ts.c
> @@ -1356,7 +1356,7 @@ static int mxt_prepare_cfg_mem(struct mxt_data *data,
>  
>  			byte_offset = reg + i - cfg_start_ofs;
>  
> -			if (byte_offset >= 0 && byte_offset < config_mem_size) {
> +			if (byte_offset < config_mem_size) {
>  				*(config_mem + byte_offset) = val;
>  			} else {
>  				dev_err(dev, "Bad object: reg:%d, T%d, ofs=%d\n",
> -- 
> 2.7.4
> 

^ permalink raw reply	[flat|nested] 4+ messages in thread
* Re: [PATCH] Input: atmel_mxt_ts - Remove unnecessary byte_offset check
  2017-10-08 19:41 ` Nick Dyer
@ 2017-10-09 17:38   ` Dmitry Torokhov
  2017-10-09 21:06     ` Christos Gkekas
  0 siblings, 1 reply; 4+ messages in thread
From: Dmitry Torokhov @ 2017-10-09 17:38 UTC (permalink / raw)
  To: Nick Dyer; +Cc: Christos Gkekas, linux-input, linux-kernel

On Sun, Oct 08, 2017 at 08:41:16PM +0100, Nick Dyer wrote:
> On Sun, Oct 08, 2017 at 07:44:18PM +0100, Christos Gkekas wrote:
> > Variable byte_offset is unsigned so checking whether it is greater or
> > equal to zero is redundant.
> > 
> > Signed-off-by: Christos Gkekas <chris.gekas@gmail.com>
> 
> Yep - looks sensible to me.
> 
> Signed-off-by: Nick Dyer <nick@shmanahar.org>

I believe this has been discussed before and Linus told us to keep the
such checks as is: they neatly document the ranges of values, safe in
case we ever change the type of the variables, and do not cost us
anything at execution time.


> 
> > ---
> >  drivers/input/touchscreen/atmel_mxt_ts.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/touchscreen/atmel_mxt_ts.c
> > index 7659bc4..baafaed 100644
> > --- a/drivers/input/touchscreen/atmel_mxt_ts.c
> > +++ b/drivers/input/touchscreen/atmel_mxt_ts.c
> > @@ -1356,7 +1356,7 @@ static int mxt_prepare_cfg_mem(struct mxt_data *data,
> >  
> >  			byte_offset = reg + i - cfg_start_ofs;
> >  
> > -			if (byte_offset >= 0 && byte_offset < config_mem_size) {
> > +			if (byte_offset < config_mem_size) {
> >  				*(config_mem + byte_offset) = val;
> >  			} else {
> >  				dev_err(dev, "Bad object: reg:%d, T%d, ofs=%d\n",
> > -- 
> > 2.7.4
> > 

Thanks.

-- 
Dmitry

^ permalink raw reply	[flat|nested] 4+ messages in thread
* Re: [PATCH] Input: atmel_mxt_ts - Remove unnecessary byte_offset check
  2017-10-09 17:38   ` Dmitry Torokhov
@ 2017-10-09 21:06     ` Christos Gkekas
  0 siblings, 0 replies; 4+ messages in thread
From: Christos Gkekas @ 2017-10-09 21:06 UTC (permalink / raw)
  To: Dmitry Torokhov; +Cc: Nick Dyer, linux-input, linux-kernel

On 09/10/17 10:38:55 -0700, Dmitry Torokhov wrote:
> On Sun, Oct 08, 2017 at 08:41:16PM +0100, Nick Dyer wrote:
> > On Sun, Oct 08, 2017 at 07:44:18PM +0100, Christos Gkekas wrote:
> > > Variable byte_offset is unsigned so checking whether it is greater or
> > > equal to zero is redundant.
> > > 
> > > Signed-off-by: Christos Gkekas <chris.gekas@gmail.com>
> > 
> > Yep - looks sensible to me.
> > 
> > Signed-off-by: Nick Dyer <nick@shmanahar.org>
> 
> I believe this has been discussed before and Linus told us to keep the
> such checks as is: they neatly document the ranges of values, safe in
> case we ever change the type of the variables, and do not cost us
> anything at execution time.
> 

Fair enough, thanks for your feedback.

I believe you are referring to this:
https://lkml.org/lkml/2006/11/28/206

Regards,
Christos

> 
> > 
> > > ---
> > >  drivers/input/touchscreen/atmel_mxt_ts.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/touchscreen/atmel_mxt_ts.c
> > > index 7659bc4..baafaed 100644
> > > --- a/drivers/input/touchscreen/atmel_mxt_ts.c
> > > +++ b/drivers/input/touchscreen/atmel_mxt_ts.c
> > > @@ -1356,7 +1356,7 @@ static int mxt_prepare_cfg_mem(struct mxt_data *data,
> > >  
> > >  			byte_offset = reg + i - cfg_start_ofs;
> > >  
> > > -			if (byte_offset >= 0 && byte_offset < config_mem_size) {
> > > +			if (byte_offset < config_mem_size) {
> > >  				*(config_mem + byte_offset) = val;
> > >  			} else {
> > >  				dev_err(dev, "Bad object: reg:%d, T%d, ofs=%d\n",
> > > -- 
> > > 2.7.4
> > > 
> 
> Thanks.
> 
> -- 
> Dmitry

^ permalink raw reply	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2017-10-09 21:06 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-10-08 18:44 [PATCH] Input: atmel_mxt_ts - Remove unnecessary byte_offset check Christos Gkekas
2017-10-08 19:41 ` Nick Dyer
2017-10-09 17:38   ` Dmitry Torokhov
2017-10-09 21:06     ` Christos Gkekas

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