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[PATCH 29/38] Input: touchscreen: atmel: remove invalid check

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  [PATCH 29/38] Input: touchscreen: atmel: remove invalid check Andrzej Hajda <a.hajda@samsung.com> - 2015-09-21 15:50 +0200
    Re: [PATCH 29/38] Input: touchscreen: atmel: remove invalid check Dmitry Torokhov <dmitry.torokhov@gmail.com> - 2015-09-21 19:20 +0200

#1229338 — [PATCH 29/38] Input: touchscreen: atmel: remove invalid check

byte_offset is unsigned.

The problem has been detected using proposed semantic patch
scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].

[1]: http://permalink.gmane.org/gmane.linux.kernel/2038576

Signed-off-by: Andrzej Hajda <a.hajda@samsung.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 c562205..c577f95 100644
--- a/drivers/input/touchscreen/atmel_mxt_ts.c
+++ b/drivers/input/touchscreen/atmel_mxt_ts.c
@@ -1267,7 +1267,7 @@ 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",
-- 
1.9.1

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#1229583

Hi Andrzej,

On Mon, Sep 21, 2015 at 03:34:01PM +0200, Andrzej Hajda wrote:
> byte_offset is unsigned.
> 
> The problem has been detected using proposed semantic patch
> scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].
> 
> [1]: http://permalink.gmane.org/gmane.linux.kernel/2038576
> 
> Signed-off-by: Andrzej Hajda <a.hajda@samsung.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 c562205..c577f95 100644
> --- a/drivers/input/touchscreen/atmel_mxt_ts.c
> +++ b/drivers/input/touchscreen/atmel_mxt_ts.c
> @@ -1267,7 +1267,7 @@ 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) {

I'd rather we kept the check as is: it documents the expected range even
if one of the checks is always true. If you search the archives you'll
find Linus has also pretty strong opinion about these checks actually
being useful from documenting POV.


>  				*(config_mem + byte_offset) = val;
>  			} else {
>  				dev_err(dev, "Bad object: reg:%d, T%d, ofs=%d\n",
> -- 
> 1.9.1
> 

Thanks.

-- 
Dmitry
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