[1/4] Remove redundant return value check

  media_entity_pads_init() will not return 0 only if the
2nd parameter >= MEDIA_ENTITY_MAX_PADS (512), but 1 is
passed, so checking the return value is redundant

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: ad85094b293e ("Revert "media: staging: atomisp: Remove driver"")
Signed-off-by: Alexandra Diupina <adiupina@astralinux.ru>
---
 drivers/staging/media/atomisp/i2c/atomisp-gc2235.c        | 4 +---
 drivers/staging/media/atomisp/i2c/atomisp-mt9m114.c       | 6 +-----
 drivers/staging/media/atomisp/i2c/atomisp-ov2722.c        | 2 --
 drivers/staging/media/atomisp/i2c/ov5693/atomisp-ov5693.c | 2 --
 4 files changed, 2 insertions(+), 12 deletions(-)
  

Hi Alexandra,

On 11/2/23 15:11, Alexandra Diupina wrote:
> media_entity_pads_init() will not return 0 only if the
> 2nd parameter >= MEDIA_ENTITY_MAX_PADS (512), but 1 is
> passed, so checking the return value is redundant

Generally speaking functions which can fail should always be
error-checked even if their invocation today happen to be
such that they will not fail.

Either the invocation or the function itself my change
causing it to fail in the future. Which is why we want
to keep the error checks.

But maybe media_entity_pads_init() is special and
does not need to be error checked.

Sakari, Laurent do you have any opinion on this ?

> Found by Linux Verification Center (linuxtesting.org) with SVACE.

This feels like a false positive of the tool to me,
but lets wait and see what Sakari or Laurent have
to say.

Regards,

Hans



> 
> Fixes: ad85094b293e ("Revert "media: staging: atomisp: Remove driver"")
> Signed-off-by: Alexandra Diupina <adiupina@astralinux.ru>
> ---
>  drivers/staging/media/atomisp/i2c/atomisp-gc2235.c        | 4 +---
>  drivers/staging/media/atomisp/i2c/atomisp-mt9m114.c       | 6 +-----
>  drivers/staging/media/atomisp/i2c/atomisp-ov2722.c        | 2 --
>  drivers/staging/media/atomisp/i2c/ov5693/atomisp-ov5693.c | 2 --
>  4 files changed, 2 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/staging/media/atomisp/i2c/atomisp-gc2235.c b/drivers/staging/media/atomisp/i2c/atomisp-gc2235.c
> index 9fa390fbc5f3..f10931a03285 100644
> --- a/drivers/staging/media/atomisp/i2c/atomisp-gc2235.c
> +++ b/drivers/staging/media/atomisp/i2c/atomisp-gc2235.c
> @@ -840,9 +840,7 @@ static int gc2235_probe(struct i2c_client *client)
>  	dev->ctrl_handler.lock = &dev->input_lock;
>  	dev->sd.ctrl_handler = &dev->ctrl_handler;
>  
> -	ret = media_entity_pads_init(&dev->sd.entity, 1, &dev->pad);
> -	if (ret)
> -		gc2235_remove(client);
> +	media_entity_pads_init(&dev->sd.entity, 1, &dev->pad);
>  
>  	return atomisp_register_i2c_module(&dev->sd, gcpdev, RAW_CAMERA);
>  
> diff --git a/drivers/staging/media/atomisp/i2c/atomisp-mt9m114.c b/drivers/staging/media/atomisp/i2c/atomisp-mt9m114.c
> index 1c6643c442ef..b7a940fdbd0a 100644
> --- a/drivers/staging/media/atomisp/i2c/atomisp-mt9m114.c
> +++ b/drivers/staging/media/atomisp/i2c/atomisp-mt9m114.c
> @@ -1581,11 +1581,7 @@ static int mt9m114_probe(struct i2c_client *client)
>  
>  	/* REVISIT: Do we need media controller? */
>  	ret = media_entity_pads_init(&dev->sd.entity, 1, &dev->pad);
> -	if (ret) {
> -		mt9m114_remove(client);
> -		return ret;
> -	}
> -	return 0;
> +	return ret;
>  }
>  
>  static const struct acpi_device_id mt9m114_acpi_match[] = {
> diff --git a/drivers/staging/media/atomisp/i2c/atomisp-ov2722.c b/drivers/staging/media/atomisp/i2c/atomisp-ov2722.c
> index 6a72691ed5b7..922774293bf4 100644
> --- a/drivers/staging/media/atomisp/i2c/atomisp-ov2722.c
> +++ b/drivers/staging/media/atomisp/i2c/atomisp-ov2722.c
> @@ -993,8 +993,6 @@ static int ov2722_probe(struct i2c_client *client)
>  	dev->sd.entity.function = MEDIA_ENT_F_CAM_SENSOR;
>  
>  	ret = media_entity_pads_init(&dev->sd.entity, 1, &dev->pad);
> -	if (ret)
> -		ov2722_remove(client);
>  
>  	return atomisp_register_i2c_module(&dev->sd, ovpdev, RAW_CAMERA);
>  
> diff --git a/drivers/staging/media/atomisp/i2c/ov5693/atomisp-ov5693.c b/drivers/staging/media/atomisp/i2c/ov5693/atomisp-ov5693.c
> index 460a4e34c55b..8d5b74fb5d9c 100644
> --- a/drivers/staging/media/atomisp/i2c/ov5693/atomisp-ov5693.c
> +++ b/drivers/staging/media/atomisp/i2c/ov5693/atomisp-ov5693.c
> @@ -1733,8 +1733,6 @@ static int ov5693_probe(struct i2c_client *client)
>  	dev->sd.ctrl_handler = &dev->ctrl_handler;
>  
>  	ret = media_entity_pads_init(&dev->sd.entity, 1, &dev->pad);
> -	if (ret)
> -		ov5693_remove(client);
>  
>  	return ret;
>  out_free:
  

On Thu, Nov 02, 2023 at 05:11:32PM +0300, Alexandra Diupina wrote:
> media_entity_pads_init() will not return 0 only if the
> 2nd parameter >= MEDIA_ENTITY_MAX_PADS (512), but 1 is
> passed, so checking the return value is redundant
> 

It can return an error because of this check:

drivers/media/mc/mc-entity.c
   215                  if (hweight32(iter->flags & (MEDIA_PAD_FL_SINK |
   216                                               MEDIA_PAD_FL_SOURCE)) != 1) {
   217                          ret = -EINVAL;
   218                          break;
   219                  }

Plus I don't like removing error checking for this reason.

Earlier this month I fixed a case where someone removed an IS_ERR()
check but then we modified the function to return error pointers.
https://lore.kernel.org/all/356fb42c-9cf1-45cd-9233-ac845c507fb7@moroto.mountain/

regards,
dan carpenter
  

On Thu, Nov 02, 2023 at 05:11:32PM +0300, Alexandra Diupina wrote:
> media_entity_pads_init() will not return 0 only if the
> 2nd parameter >= MEDIA_ENTITY_MAX_PADS (512), but 1 is
> passed, so checking the return value is redundant
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: ad85094b293e ("Revert "media: staging: atomisp: Remove driver"")
> Signed-off-by: Alexandra Diupina <adiupina@astralinux.ru>
> ---
>  drivers/staging/media/atomisp/i2c/atomisp-gc2235.c        | 4 +---
>  drivers/staging/media/atomisp/i2c/atomisp-mt9m114.c       | 6 +-----
>  drivers/staging/media/atomisp/i2c/atomisp-ov2722.c        | 2 --
>  drivers/staging/media/atomisp/i2c/ov5693/atomisp-ov5693.c | 2 --
>  4 files changed, 2 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/staging/media/atomisp/i2c/atomisp-gc2235.c b/drivers/staging/media/atomisp/i2c/atomisp-gc2235.c
> index 9fa390fbc5f3..f10931a03285 100644
> --- a/drivers/staging/media/atomisp/i2c/atomisp-gc2235.c
> +++ b/drivers/staging/media/atomisp/i2c/atomisp-gc2235.c
> @@ -840,9 +840,7 @@ static int gc2235_probe(struct i2c_client *client)
>  	dev->ctrl_handler.lock = &dev->input_lock;
>  	dev->sd.ctrl_handler = &dev->ctrl_handler;
>  
> -	ret = media_entity_pads_init(&dev->sd.entity, 1, &dev->pad);
> -	if (ret)
> -		gc2235_remove(client);

Not related to your patch but why doesn't this error path return an
error?  Can that be right?

> +	media_entity_pads_init(&dev->sd.entity, 1, &dev->pad);
>  
>  	return atomisp_register_i2c_module(&dev->sd, gcpdev, RAW_CAMERA);

regards,
dan carpenter
  

Hi Dan,

On 11/2/23 15:35, Dan Carpenter wrote:
> On Thu, Nov 02, 2023 at 05:11:32PM +0300, Alexandra Diupina wrote:
>> media_entity_pads_init() will not return 0 only if the
>> 2nd parameter >= MEDIA_ENTITY_MAX_PADS (512), but 1 is
>> passed, so checking the return value is redundant
>>
>> Found by Linux Verification Center (linuxtesting.org) with SVACE.
>>
>> Fixes: ad85094b293e ("Revert "media: staging: atomisp: Remove driver"")
>> Signed-off-by: Alexandra Diupina <adiupina@astralinux.ru>
>> ---
>>  drivers/staging/media/atomisp/i2c/atomisp-gc2235.c        | 4 +---
>>  drivers/staging/media/atomisp/i2c/atomisp-mt9m114.c       | 6 +-----
>>  drivers/staging/media/atomisp/i2c/atomisp-ov2722.c        | 2 --
>>  drivers/staging/media/atomisp/i2c/ov5693/atomisp-ov5693.c | 2 --
>>  4 files changed, 2 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/staging/media/atomisp/i2c/atomisp-gc2235.c b/drivers/staging/media/atomisp/i2c/atomisp-gc2235.c
>> index 9fa390fbc5f3..f10931a03285 100644
>> --- a/drivers/staging/media/atomisp/i2c/atomisp-gc2235.c
>> +++ b/drivers/staging/media/atomisp/i2c/atomisp-gc2235.c
>> @@ -840,9 +840,7 @@ static int gc2235_probe(struct i2c_client *client)
>>  	dev->ctrl_handler.lock = &dev->input_lock;
>>  	dev->sd.ctrl_handler = &dev->ctrl_handler;
>>  
>> -	ret = media_entity_pads_init(&dev->sd.entity, 1, &dev->pad);
>> -	if (ret)
>> -		gc2235_remove(client);
> 
> Not related to your patch but why doesn't this error path return an
> error?  Can that be right?

This is staging code and there are multiple camera sensor drivers under
drivers/staging/media/atomisp/i2c/

The gc2235 driver is one of the drivers which I have not yes tested
(I do have hw to test it, just no time), let alone worked on cleaning
it up...

Regards,

Hans
  

Hi Hans, Alexandra,

On Thu, Nov 02, 2023 at 03:21:04PM +0100, Hans de Goede wrote:
> Hi Alexandra,
> 
> On 11/2/23 15:11, Alexandra Diupina wrote:
> > media_entity_pads_init() will not return 0 only if the
> > 2nd parameter >= MEDIA_ENTITY_MAX_PADS (512), but 1 is
> > passed, so checking the return value is redundant
> 
> Generally speaking functions which can fail should always be
> error-checked even if their invocation today happen to be
> such that they will not fail.
> 
> Either the invocation or the function itself my change
> causing it to fail in the future. Which is why we want
> to keep the error checks.
> 
> But maybe media_entity_pads_init() is special and
> does not need to be error checked.
> 
> Sakari, Laurent do you have any opinion on this ?
> 
> > Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> This feels like a false positive of the tool to me,
> but lets wait and see what Sakari or Laurent have
> to say.

I agree with Hans: this function today may not fail with the parameters
passed to it but it may happen in the future. In general it's good to check
a return value of a function that returns one: if that function is changed,
no-one will go through the callers as long as the arguments and the return
value remain the same.
  

Hello Alexandra,

it would be great if you could improve the Subject line for the next
patch submission round by using an appropriate prefix. Currently at
least three of the four patches in this series have "Remove redundant
return value check" as Subject/commit short log. (I didn't get patch
3/4.) Something like

	media: atomisp: i2c: Remove redundant return value check

seems to be appropriate for this patch.

You make life easier for the recipients of your patch because it becomes
easier to see if you're responsible for this patch or not. So you're
wasting less time for people like me who have no further interest in
this patch set and the maintainers of the affected drivers immediately
see what was touched. That's a win for everybody; including you.

Best regards
Uwe