[PATCH][next] drm/rockchip: Remove redundant assignment of pointer connector

[PATCH][next] drm/rockchip: Remove redundant assignment of pointer connector

[Colin King]

From: Colin Ian King <colin.king@canonical.com>

The pointer connector is being assigned a value that is never
read, it is being updated immediately afterwards. The assignment
is redundant and can be removed.

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 drivers/gpu/drm/rockchip/rockchip_rgb.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/gpu/drm/rockchip/rockchip_rgb.c b/drivers/gpu/drm/rockchip/rockchip_rgb.c
index 09be9678f2bd..18fb84068a64 100644
--- a/drivers/gpu/drm/rockchip/rockchip_rgb.c
+++ b/drivers/gpu/drm/rockchip/rockchip_rgb.c
@@ -150,7 +150,6 @@ struct rockchip_rgb *rockchip_rgb_init(struct device *dev,
 	if (ret)
 		goto err_free_encoder;
 
-	connector = &rgb->connector;
 	connector = drm_bridge_connector_init(rgb->drm_dev, encoder);
 	if (IS_ERR(connector)) {
 		DRM_DEV_ERROR(drm_dev->dev,
-- 
2.32.0

Re: [PATCH][next] drm/rockchip: Remove redundant assignment of pointer connector

[Alex Bee]

Hi Colin,
Am 22.09.21 um 13:24 schrieb Colin King:
> From: Colin Ian King <colin.king@canonical.com>
> 
> The pointer connector is being assigned a value that is never
> read, it is being updated immediately afterwards. The assignment
> is redundant and can be removed.

The pointer to the connector is used in rockchip_rgb_fini for 
drm_connector_cleanup.
It's pretty much the same for the encoder, btw.

Regards,

Alex
> 
> Addresses-Coverity: ("Unused value")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
>   drivers/gpu/drm/rockchip/rockchip_rgb.c | 1 -
>   1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/rockchip/rockchip_rgb.c b/drivers/gpu/drm/rockchip/rockchip_rgb.c
> index 09be9678f2bd..18fb84068a64 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_rgb.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_rgb.c
> @@ -150,7 +150,6 @@ struct rockchip_rgb *rockchip_rgb_init(struct device *dev,
>   	if (ret)
>   		goto err_free_encoder;
>   
> -	connector = &rgb->connector;
>   	connector = drm_bridge_connector_init(rgb->drm_dev, encoder);
>   	if (IS_ERR(connector)) {
>   		DRM_DEV_ERROR(drm_dev->dev,
> 

Re: [PATCH][next] drm/rockchip: Remove redundant assignment of pointer connector

[Heiko Stübner]

Hi Alex,

Am Mittwoch, 22. September 2021, 18:35:38 CEST schrieb Alex Bee:
> Hi Colin,
> Am 22.09.21 um 13:24 schrieb Colin King:
> > From: Colin Ian King <colin.king@canonical.com>
> > 
> > The pointer connector is being assigned a value that is never
> > read, it is being updated immediately afterwards. The assignment
> > is redundant and can be removed.
> 
> The pointer to the connector is used in rockchip_rgb_fini for 
> drm_connector_cleanup.
> It's pretty much the same for the encoder, btw.

I think the issue is more the two lines

	connector = &rgb->connector;
 	connector = drm_bridge_connector_init(rgb->drm_dev, encoder);

hence the connector = &rgb->connector being overwritten immediately after

Now that I look at it again, the whole approach looks strange.
drm_bridge_connector_init() creates the connector structure and
returns a pointer to it.

So the first line below sets the connector pointer to point to the
&rgb->connector element and the second line then set a completely
different address into it.

So the connector element in rockchip_lvds and rockchip_rgb should actually
become a pointer itself to hold the connector element returned from
drm_bridge_connector_init() .


Heiko

> 
> Regards,
> 
> Alex
> > 
> > Addresses-Coverity: ("Unused value")
> > Signed-off-by: Colin Ian King <colin.king@canonical.com>
> > ---
> >   drivers/gpu/drm/rockchip/rockchip_rgb.c | 1 -
> >   1 file changed, 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/rockchip/rockchip_rgb.c b/drivers/gpu/drm/rockchip/rockchip_rgb.c
> > index 09be9678f2bd..18fb84068a64 100644
> > --- a/drivers/gpu/drm/rockchip/rockchip_rgb.c
> > +++ b/drivers/gpu/drm/rockchip/rockchip_rgb.c
> > @@ -150,7 +150,6 @@ struct rockchip_rgb *rockchip_rgb_init(struct device *dev,
> >   	if (ret)
> >   		goto err_free_encoder;
> >   
> > -	connector = &rgb->connector;
> >   	connector = drm_bridge_connector_init(rgb->drm_dev, encoder);
> >   	if (IS_ERR(connector)) {
> >   		DRM_DEV_ERROR(drm_dev->dev,
> > 
> 
> 

Re: [PATCH][next] drm/rockchip: Remove redundant assignment of pointer connector

[Alex Bee]

Hi Heiko,

Am 22.09.21 um 18:45 schrieb Heiko Stübner:
> Hi Alex,
>
> Am Mittwoch, 22. September 2021, 18:35:38 CEST schrieb Alex Bee:
>> Hi Colin,
>> Am 22.09.21 um 13:24 schrieb Colin King:
>>> From: Colin Ian King <colin.king@canonical.com>
>>>
>>> The pointer connector is being assigned a value that is never
>>> read, it is being updated immediately afterwards. The assignment
>>> is redundant and can be removed.
>> The pointer to the connector is used in rockchip_rgb_fini for
>> drm_connector_cleanup.
>> It's pretty much the same for the encoder, btw.
> I think the issue is more the two lines
>
> 	connector = &rgb->connector;
>   	connector = drm_bridge_connector_init(rgb->drm_dev, encoder);
>
> hence the connector = &rgb->connector being overwritten immediately after
>
> Now that I look at it again, the whole approach looks strange.
> drm_bridge_connector_init() creates the connector structure and
> returns a pointer to it.

Totally agreed.

The main reason I was doing it that way, was the way it was done already 
in rockchip_lvds.c, where the connector was already existent in the 
struct rockchip_lvds (and was already used in the panel-case - all 
places where it is used accept pointers also, btw) and is *no* pointer - 
and is done already this very strange way.

I wanted to re-use it for the bridge-case and didn't want to differ in 
coding in rockchip-rgb to much.

The only reason I can think of, why it was done that way is, that we 
might need a pointer to a fully initialized struct drm_connector for 
some reason (drm_connector_cleanup ?), what we wouldn't have if have 
just a pointer and something goes wrong before drm_connector_init 
respectivly drm_bridge_connector_init.

Alex


> So the first line below sets the connector pointer to point to the
> &rgb->connector element and the second line then set a completely
> different address into it.
>
> So the connector element in rockchip_lvds and rockchip_rgb should actually
> become a pointer itself to hold the connector element returned from
> drm_bridge_connector_init() .
>
>
> Heiko
>
>> Regards,
>>
>> Alex
>>> Addresses-Coverity: ("Unused value")
>>> Signed-off-by: Colin Ian King <colin.king@canonical.com>
>>> ---
>>>    drivers/gpu/drm/rockchip/rockchip_rgb.c | 1 -
>>>    1 file changed, 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/rockchip/rockchip_rgb.c b/drivers/gpu/drm/rockchip/rockchip_rgb.c
>>> index 09be9678f2bd..18fb84068a64 100644
>>> --- a/drivers/gpu/drm/rockchip/rockchip_rgb.c
>>> +++ b/drivers/gpu/drm/rockchip/rockchip_rgb.c
>>> @@ -150,7 +150,6 @@ struct rockchip_rgb *rockchip_rgb_init(struct device *dev,
>>>    	if (ret)
>>>    		goto err_free_encoder;
>>>    
>>> -	connector = &rgb->connector;
>>>    	connector = drm_bridge_connector_init(rgb->drm_dev, encoder);
>>>    	if (IS_ERR(connector)) {
>>>    		DRM_DEV_ERROR(drm_dev->dev,
>>>
>>
>
>
>

Re: [PATCH][next] drm/rockchip: Remove redundant assignment of pointer connector

[Alex Bee]

Hi all,

Am 22.09.21 um 19:31 schrieb Alex Bee:
> Hi Heiko,
>
> Am 22.09.21 um 18:45 schrieb Heiko Stübner:
>> Hi Alex,
>>
>> Am Mittwoch, 22. September 2021, 18:35:38 CEST schrieb Alex Bee:
>>> Hi Colin,
>>> Am 22.09.21 um 13:24 schrieb Colin King:
>>>> From: Colin Ian King <colin.king@canonical.com>
>>>>
>>>> The pointer connector is being assigned a value that is never
>>>> read, it is being updated immediately afterwards. The assignment
>>>> is redundant and can be removed.
>>> The pointer to the connector is used in rockchip_rgb_fini for
>>> drm_connector_cleanup.
>>> It's pretty much the same for the encoder, btw.
>> I think the issue is more the two lines
>>
>>     connector = &rgb->connector;
>>       connector = drm_bridge_connector_init(rgb->drm_dev, encoder);
>>
>> hence the connector = &rgb->connector being overwritten immediately 
>> after
>>
>> Now that I look at it again, the whole approach looks strange.
>> drm_bridge_connector_init() creates the connector structure and
>> returns a pointer to it.
>
> Totally agreed.
>
> The main reason I was doing it that way, was the way it was done 
> already in rockchip_lvds.c, where the connector was already existent 
> in the struct rockchip_lvds (and was already used in the panel-case - 
> all places where it is used accept pointers also, btw) and is *no* 
> pointer - and is done already this very strange way.
>
> I wanted to re-use it for the bridge-case and didn't want to differ in 
> coding in rockchip-rgb to much.
>
> The only reason I can think of, why it was done that way is, that we 
> might need a pointer to a fully initialized struct drm_connector for 
> some reason (drm_connector_cleanup ?), what we wouldn't have if have 
> just a pointer and something goes wrong before drm_connector_init 
> respectivly drm_bridge_connector_init.
>
> Alex
>
>
>> So the first line below sets the connector pointer to point to the
>> &rgb->connector element and the second line then set a completely
>> different address into it.
>>
>> So the connector element in rockchip_lvds and rockchip_rgb should 
>> actually
>> become a pointer itself to hold the connector element returned from
>> drm_bridge_connector_init() .
It turns out, nothing bad happens (i.e. rockchip_rgb_fini, the only 
place where the connector is also used, isn't called if 
rockchip_rgb_init fails) - so it will be OK if we make the connector a 
pointer in struct rockchip_rgb. But we'll need to keep it a "full" 
struct drm_connector in struct rockchip_lvds, since in case it's a 
panel  it gets properties assigend before drm_connector_init is called 
and should for that reason initialized before.

I'll send a patch soon.

Alex

>>
>>
>> Heiko
>>
>>> Regards,
>>>
>>> Alex
>>>> Addresses-Coverity: ("Unused value")
>>>> Signed-off-by: Colin Ian King <colin.king@canonical.com>
>>>> ---
>>>>    drivers/gpu/drm/rockchip/rockchip_rgb.c | 1 -
>>>>    1 file changed, 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/rockchip/rockchip_rgb.c 
>>>> b/drivers/gpu/drm/rockchip/rockchip_rgb.c
>>>> index 09be9678f2bd..18fb84068a64 100644
>>>> --- a/drivers/gpu/drm/rockchip/rockchip_rgb.c
>>>> +++ b/drivers/gpu/drm/rockchip/rockchip_rgb.c
>>>> @@ -150,7 +150,6 @@ struct rockchip_rgb *rockchip_rgb_init(struct 
>>>> device *dev,
>>>>        if (ret)
>>>>            goto err_free_encoder;
>>>>    -    connector = &rgb->connector;
>>>>        connector = drm_bridge_connector_init(rgb->drm_dev, encoder);
>>>>        if (IS_ERR(connector)) {
>>>>            DRM_DEV_ERROR(drm_dev->dev,
>>>>
>>>
>>
>>
>>