diff mbox

drm/i915: fix a read size argument

Message ID 20161013085508.GJ16198@mwanda (mailing list archive)
State New, archived
Headers show

Commit Message

Dan Carpenter Oct. 13, 2016, 8:55 a.m. UTC 
We want to read 3 bytes here, but because the parenthesis are in the
wrong place we instead read:

	sizeof(intel_dp->edp_dpcd) == sizeof(intel_dp->edp_dpcd)

which is one byte.

Fixes: fe5a66f91c88 ("drm/i915: Read PSR caps/intermediate freqs/etc. only once on eDP")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

Comments

Chris Wilson Oct. 13, 2016, 9:01 a.m. UTC | #1 
On Thu, Oct 13, 2016 at 11:55:08AM +0300, Dan Carpenter wrote:
> We want to read 3 bytes here, but because the parenthesis are in the
> wrong place we instead read:
> 
> 	sizeof(intel_dp->edp_dpcd) == sizeof(intel_dp->edp_dpcd)
> 
> which is one byte.
> 
> Fixes: fe5a66f91c88 ("drm/i915: Read PSR caps/intermediate freqs/etc. only once on eDP")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

Oops, does smatch catch this? I don't recall seeing the complaint in
recent runs?

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
-Chris
Eric Engestrom Oct. 13, 2016, 9:07 a.m. UTC | #2 
On Thu, Oct 13, 2016 at 11:55:08AM +0300, Dan Carpenter wrote:
> We want to read 3 bytes here, but because the parenthesis are in the
> wrong place we instead read:
> 
> 	sizeof(intel_dp->edp_dpcd) == sizeof(intel_dp->edp_dpcd)
> 
> which is one byte.
> 
> Fixes: fe5a66f91c88 ("drm/i915: Read PSR caps/intermediate freqs/etc. only once on eDP")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

Good catch!  What tool did you use to find it, or did you find it by
inspection?
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>

(btw, there's a missing `---` here, between the commit msg and the diff)

> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 14a3cf0..ee8aa95 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -3551,8 +3551,8 @@ intel_edp_init_dpcd(struct intel_dp *intel_dp)
>  	/* Read the eDP Display control capabilities registers */
>  	if ((intel_dp->dpcd[DP_EDP_CONFIGURATION_CAP] & DP_DPCD_DISPLAY_CONTROL_CAPABLE) &&
>  	    drm_dp_dpcd_read(&intel_dp->aux, DP_EDP_DPCD_REV,
> -			     intel_dp->edp_dpcd, sizeof(intel_dp->edp_dpcd) ==
> -			     sizeof(intel_dp->edp_dpcd)))
> +			     intel_dp->edp_dpcd, sizeof(intel_dp->edp_dpcd)) ==
> +			     sizeof(intel_dp->edp_dpcd))
>  		DRM_DEBUG_KMS("EDP DPCD : %*ph\n", (int) sizeof(intel_dp->edp_dpcd),
>  			      intel_dp->edp_dpcd);
Walter Harms Oct. 13, 2016, 9:27 a.m. UTC | #3 
Am 13.10.2016 10:55, schrieb Dan Carpenter:
> We want to read 3 bytes here, but because the parenthesis are in the
> wrong place we instead read:
> 
> 	sizeof(intel_dp->edp_dpcd) == sizeof(intel_dp->edp_dpcd)
> 
> which is one byte.
> 
> Fixes: fe5a66f91c88 ("drm/i915: Read PSR caps/intermediate freqs/etc. only once on eDP")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 14a3cf0..ee8aa95 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -3551,8 +3551,8 @@ intel_edp_init_dpcd(struct intel_dp *intel_dp)
>  	/* Read the eDP Display control capabilities registers */
>  	if ((intel_dp->dpcd[DP_EDP_CONFIGURATION_CAP] & DP_DPCD_DISPLAY_CONTROL_CAPABLE) &&
>  	    drm_dp_dpcd_read(&intel_dp->aux, DP_EDP_DPCD_REV,
> -			     intel_dp->edp_dpcd, sizeof(intel_dp->edp_dpcd) ==
> -			     sizeof(intel_dp->edp_dpcd)))
> +			     intel_dp->edp_dpcd, sizeof(intel_dp->edp_dpcd)) ==
> +			     sizeof(intel_dp->edp_dpcd))



perhaps we can morph that into something more readable ? I would suggest:


if (intel_dp->dpcd[DP_EDP_CONFIGURATION_CAP] & DP_DPCD_DISPLAY_CONTROL_CAPABLE)
  {
    size_t size=sizeof(intel_dp->edp_dpcd); /* == EDP_DISPLAY_CTL_CAP_SIZE */
    int ret;	

    ret=drm_dp_dpcd_read(&intel_dp->aux, DP_EDP_DPCD_REV,intel_dp->edp_dpcd,size);	

    if (ret != size )
        ......

 }

this way it improves readability and reduces line length.


>  		DRM_DEBUG_KMS("EDP DPCD : %*ph\n", (int) sizeof(intel_dp->edp_dpcd),
>  			      intel_dp->edp_dpcd);
>  
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Dan Carpenter Oct. 13, 2016, 9:58 a.m. UTC | #4 
On Thu, Oct 13, 2016 at 10:01:03AM +0100, Chris Wilson wrote:
> On Thu, Oct 13, 2016 at 11:55:08AM +0300, Dan Carpenter wrote:
> > We want to read 3 bytes here, but because the parenthesis are in the
> > wrong place we instead read:
> > 
> > 	sizeof(intel_dp->edp_dpcd) == sizeof(intel_dp->edp_dpcd)
> > 
> > which is one byte.
> > 
> > Fixes: fe5a66f91c88 ("drm/i915: Read PSR caps/intermediate freqs/etc. only once on eDP")
> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> 
> Oops, does smatch catch this?

Yeah.  It does.

regards,
dan carpenter
Jani Nikula Oct. 13, 2016, 12:13 p.m. UTC | #5 
On Thu, 13 Oct 2016, walter harms <wharms@bfs.de> wrote:
> Am 13.10.2016 10:55, schrieb Dan Carpenter:
>> We want to read 3 bytes here, but because the parenthesis are in the
>> wrong place we instead read:
>> 
>> 	sizeof(intel_dp->edp_dpcd) == sizeof(intel_dp->edp_dpcd)
>> 
>> which is one byte.
>> 
>> Fixes: fe5a66f91c88 ("drm/i915: Read PSR caps/intermediate freqs/etc. only once on eDP")
>> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

Dan, good catch, thank you. Luckily we only really use the first byte
currently...

Cc: <drm-intel-fixes@lists.freedesktop.org>

>> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
>> index 14a3cf0..ee8aa95 100644
>> --- a/drivers/gpu/drm/i915/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/intel_dp.c
>> @@ -3551,8 +3551,8 @@ intel_edp_init_dpcd(struct intel_dp *intel_dp)
>>  	/* Read the eDP Display control capabilities registers */
>>  	if ((intel_dp->dpcd[DP_EDP_CONFIGURATION_CAP] & DP_DPCD_DISPLAY_CONTROL_CAPABLE) &&
>>  	    drm_dp_dpcd_read(&intel_dp->aux, DP_EDP_DPCD_REV,
>> -			     intel_dp->edp_dpcd, sizeof(intel_dp->edp_dpcd) ==
>> -			     sizeof(intel_dp->edp_dpcd)))
>> +			     intel_dp->edp_dpcd, sizeof(intel_dp->edp_dpcd)) ==
>> +			     sizeof(intel_dp->edp_dpcd))
>
>
>
> perhaps we can morph that into something more readable ? I would suggest:
>
>
> if (intel_dp->dpcd[DP_EDP_CONFIGURATION_CAP] & DP_DPCD_DISPLAY_CONTROL_CAPABLE)
>   {
>     size_t size=sizeof(intel_dp->edp_dpcd); /* == EDP_DISPLAY_CTL_CAP_SIZE */
>     int ret;	
>
>     ret=drm_dp_dpcd_read(&intel_dp->aux, DP_EDP_DPCD_REV,intel_dp->edp_dpcd,size);	
>
>     if (ret != size )
>         ......
>
>  }
>
> this way it improves readability and reduces line length.

Not convinced, let's just take the simple brace fix now.

BR,
Jani.
diff mbox

Patch

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 14a3cf0..ee8aa95 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -3551,8 +3551,8 @@  intel_edp_init_dpcd(struct intel_dp *intel_dp)
 	/* Read the eDP Display control capabilities registers */
 	if ((intel_dp->dpcd[DP_EDP_CONFIGURATION_CAP] & DP_DPCD_DISPLAY_CONTROL_CAPABLE) &&
 	    drm_dp_dpcd_read(&intel_dp->aux, DP_EDP_DPCD_REV,
-			     intel_dp->edp_dpcd, sizeof(intel_dp->edp_dpcd) ==
-			     sizeof(intel_dp->edp_dpcd)))
+			     intel_dp->edp_dpcd, sizeof(intel_dp->edp_dpcd)) ==
+			     sizeof(intel_dp->edp_dpcd))
 		DRM_DEBUG_KMS("EDP DPCD : %*ph\n", (int) sizeof(intel_dp->edp_dpcd),
 			      intel_dp->edp_dpcd);