[PATCH] drm/simpledrm: Drop superfluous primary plane .atomic_check return logic

[PATCH] drm/simpledrm: Drop superfluous primary plane .atomic_check return logic

[Javier Martinez Canillas]

The simpledrm_primary_plane_helper_atomic_check() function is more complex
than needed. It first checks drm_atomic_helper_check_plane_state() returns
value to decide whether to return this or zero.

But it could just return that function return value directly. It also does
a check if new_plane_state->visible isn't set, but returns zero regardless.

Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
---

 drivers/gpu/drm/tiny/simpledrm.c | 15 ++++-----------
 1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/tiny/simpledrm.c b/drivers/gpu/drm/tiny/simpledrm.c
index a81f91814595..0be47f40247a 100644
--- a/drivers/gpu/drm/tiny/simpledrm.c
+++ b/drivers/gpu/drm/tiny/simpledrm.c
@@ -485,21 +485,14 @@ static int simpledrm_primary_plane_helper_atomic_check(struct drm_plane *plane,
 	struct drm_plane_state *new_plane_state = drm_atomic_get_new_plane_state(new_state, plane);
 	struct drm_crtc *new_crtc = new_plane_state->crtc;
 	struct drm_crtc_state *new_crtc_state = NULL;
-	int ret;
 
 	if (new_crtc)
 		new_crtc_state = drm_atomic_get_new_crtc_state(new_state, new_crtc);
 
-	ret = drm_atomic_helper_check_plane_state(new_plane_state, new_crtc_state,
-						  DRM_PLANE_NO_SCALING,
-						  DRM_PLANE_NO_SCALING,
-						  false, false);
-	if (ret)
-		return ret;
-	else if (!new_plane_state->visible)
-		return 0;
-
-	return 0;
+	return drm_atomic_helper_check_plane_state(new_plane_state, new_crtc_state,
+						   DRM_PLANE_NO_SCALING,
+						   DRM_PLANE_NO_SCALING,
+						   false, false);
 }
 
 static void simpledrm_primary_plane_helper_atomic_update(struct drm_plane *plane,
-- 
2.37.1

Re: [PATCH] drm/simpledrm: Drop superfluous primary plane .atomic_check return logic

[Thomas Zimmermann]

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Hi Javier

Am 31.08.22 um 13:12 schrieb Javier Martinez Canillas:
> The simpledrm_primary_plane_helper_atomic_check() function is more complex
> than needed. It first checks drm_atomic_helper_check_plane_state() returns
> value to decide whether to return this or zero.
> 
> But it could just return that function return value directly. It also does
> a check if new_plane_state->visible isn't set, but returns zero regardless.
> 
> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
> ---
> 
>   drivers/gpu/drm/tiny/simpledrm.c | 15 ++++-----------
>   1 file changed, 4 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/tiny/simpledrm.c b/drivers/gpu/drm/tiny/simpledrm.c
> index a81f91814595..0be47f40247a 100644
> --- a/drivers/gpu/drm/tiny/simpledrm.c
> +++ b/drivers/gpu/drm/tiny/simpledrm.c
> @@ -485,21 +485,14 @@ static int simpledrm_primary_plane_helper_atomic_check(struct drm_plane *plane,
>   	struct drm_plane_state *new_plane_state = drm_atomic_get_new_plane_state(new_state, plane);
>   	struct drm_crtc *new_crtc = new_plane_state->crtc;
>   	struct drm_crtc_state *new_crtc_state = NULL;
> -	int ret;
>   
>   	if (new_crtc)
>   		new_crtc_state = drm_atomic_get_new_crtc_state(new_state, new_crtc);
>   
> -	ret = drm_atomic_helper_check_plane_state(new_plane_state, new_crtc_state,
> -						  DRM_PLANE_NO_SCALING,
> -						  DRM_PLANE_NO_SCALING,
> -						  false, false);
> -	if (ret)
> -		return ret;
> -	else if (!new_plane_state->visible)
> -		return 0;
> -
> -	return 0;
> +	return drm_atomic_helper_check_plane_state(new_plane_state, new_crtc_state,
> +						   DRM_PLANE_NO_SCALING,
> +						   DRM_PLANE_NO_SCALING,
> +						   false, false);

I'm undecided on this change. I know it's correct and more to the point. 
But the call's logic is non-intuitive: the call either returns an error 
or we have to test ->visible afterwards. So I wrote it explicitly.

I saw that your change to ssd130x also uses the pattern. If we find more 
such drivers, we could implement the atomic check as a helper. I suggest 
drm_plane_helper_atomic_check_fixed() in drm_plane_helper.c

Best regards
Thomas

>   }
>   
>   static void simpledrm_primary_plane_helper_atomic_update(struct drm_plane *plane,

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

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Re: [PATCH] drm/simpledrm: Drop superfluous primary plane .atomic_check return logic

[Javier Martinez Canillas]

Hello Thomas,

On 9/5/22 12:57, Thomas Zimmermann wrote:
> Hi Javier
> 
> Am 31.08.22 um 13:12 schrieb Javier Martinez Canillas:
>> The simpledrm_primary_plane_helper_atomic_check() function is more complex
>> than needed. It first checks drm_atomic_helper_check_plane_state() returns
>> value to decide whether to return this or zero.
>>
>> But it could just return that function return value directly. It also does
>> a check if new_plane_state->visible isn't set, but returns zero regardless.
>>
>> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
>> ---
>>
>>   drivers/gpu/drm/tiny/simpledrm.c | 15 ++++-----------
>>   1 file changed, 4 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/tiny/simpledrm.c b/drivers/gpu/drm/tiny/simpledrm.c
>> index a81f91814595..0be47f40247a 100644
>> --- a/drivers/gpu/drm/tiny/simpledrm.c
>> +++ b/drivers/gpu/drm/tiny/simpledrm.c
>> @@ -485,21 +485,14 @@ static int simpledrm_primary_plane_helper_atomic_check(struct drm_plane *plane,
>>   	struct drm_plane_state *new_plane_state = drm_atomic_get_new_plane_state(new_state, plane);
>>   	struct drm_crtc *new_crtc = new_plane_state->crtc;
>>   	struct drm_crtc_state *new_crtc_state = NULL;
>> -	int ret;
>>   
>>   	if (new_crtc)
>>   		new_crtc_state = drm_atomic_get_new_crtc_state(new_state, new_crtc);
>>   
>> -	ret = drm_atomic_helper_check_plane_state(new_plane_state, new_crtc_state,
>> -						  DRM_PLANE_NO_SCALING,
>> -						  DRM_PLANE_NO_SCALING,
>> -						  false, false);
>> -	if (ret)
>> -		return ret;
>> -	else if (!new_plane_state->visible)
>> -		return 0;
>> -
>> -	return 0;
>> +	return drm_atomic_helper_check_plane_state(new_plane_state, new_crtc_state,
>> +						   DRM_PLANE_NO_SCALING,
>> +						   DRM_PLANE_NO_SCALING,
>> +						   false, false);
> 
> I'm undecided on this change. I know it's correct and more to the point. 
> But the call's logic is non-intuitive: the call either returns an error 
> or we have to test ->visible afterwards. So I wrote it explicitly.
>

Yes, but the check has no effect so I found it even less intuitive. Maybe
add a comment then if you wan to keep the current code?
 
> I saw that your change to ssd130x also uses the pattern. If we find more 
> such drivers, we could implement the atomic check as a helper. I suggest 
> drm_plane_helper_atomic_check_fixed() in drm_plane_helper.c
>

Sure. I can add a preparatory change in v2 that adds that helper and then
use it in the follow-up patch.

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat

Re: [PATCH] drm/simpledrm: Drop superfluous primary plane .atomic_check return logic

[Thomas Zimmermann]

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Hi

Am 05.09.22 um 13:06 schrieb Javier Martinez Canillas:
> Hello Thomas,
> 
> On 9/5/22 12:57, Thomas Zimmermann wrote:
>> Hi Javier
>>
>> Am 31.08.22 um 13:12 schrieb Javier Martinez Canillas:
>>> The simpledrm_primary_plane_helper_atomic_check() function is more complex
>>> than needed. It first checks drm_atomic_helper_check_plane_state() returns
>>> value to decide whether to return this or zero.
>>>
>>> But it could just return that function return value directly. It also does
>>> a check if new_plane_state->visible isn't set, but returns zero regardless.
>>>
>>> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
>>> ---
>>>
>>>    drivers/gpu/drm/tiny/simpledrm.c | 15 ++++-----------
>>>    1 file changed, 4 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/tiny/simpledrm.c b/drivers/gpu/drm/tiny/simpledrm.c
>>> index a81f91814595..0be47f40247a 100644
>>> --- a/drivers/gpu/drm/tiny/simpledrm.c
>>> +++ b/drivers/gpu/drm/tiny/simpledrm.c
>>> @@ -485,21 +485,14 @@ static int simpledrm_primary_plane_helper_atomic_check(struct drm_plane *plane,
>>>    	struct drm_plane_state *new_plane_state = drm_atomic_get_new_plane_state(new_state, plane);
>>>    	struct drm_crtc *new_crtc = new_plane_state->crtc;
>>>    	struct drm_crtc_state *new_crtc_state = NULL;
>>> -	int ret;
>>>    
>>>    	if (new_crtc)
>>>    		new_crtc_state = drm_atomic_get_new_crtc_state(new_state, new_crtc);
>>>    
>>> -	ret = drm_atomic_helper_check_plane_state(new_plane_state, new_crtc_state,
>>> -						  DRM_PLANE_NO_SCALING,
>>> -						  DRM_PLANE_NO_SCALING,
>>> -						  false, false);
>>> -	if (ret)
>>> -		return ret;
>>> -	else if (!new_plane_state->visible)
>>> -		return 0;
>>> -
>>> -	return 0;
>>> +	return drm_atomic_helper_check_plane_state(new_plane_state, new_crtc_state,
>>> +						   DRM_PLANE_NO_SCALING,
>>> +						   DRM_PLANE_NO_SCALING,
>>> +						   false, false);
>>
>> I'm undecided on this change. I know it's correct and more to the point.
>> But the call's logic is non-intuitive: the call either returns an error
>> or we have to test ->visible afterwards. So I wrote it explicitly.
>>
> 
> Yes, but the check has no effect so I found it even less intuitive. Maybe
> add a comment then if you wan to keep the current code?
>   
>> I saw that your change to ssd130x also uses the pattern. If we find more
>> such drivers, we could implement the atomic check as a helper. I suggest
>> drm_plane_helper_atomic_check_fixed() in drm_plane_helper.c
>>
> 
> Sure. I can add a preparatory change in v2 that adds that helper and then
> use it in the follow-up patch.
> 

Maybe wait for your ssd130x changes to land and then you can convert 
both drivers to the new helper.

Best regards
Thomas


-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

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Re: [PATCH] drm/simpledrm: Drop superfluous primary plane .atomic_check return logic

[Javier Martinez Canillas]

On 9/5/22 13:37, Thomas Zimmermann wrote:
> Hi
> 

[...]

>>>> -	return 0;
>>>> +	return drm_atomic_helper_check_plane_state(new_plane_state, new_crtc_state,
>>>> +						   DRM_PLANE_NO_SCALING,
>>>> +						   DRM_PLANE_NO_SCALING,
>>>> +						   false, false);
>>>
>>> I'm undecided on this change. I know it's correct and more to the point.
>>> But the call's logic is non-intuitive: the call either returns an error
>>> or we have to test ->visible afterwards. So I wrote it explicitly.
>>>
>>
>> Yes, but the check has no effect so I found it even less intuitive. Maybe
>> add a comment then if you wan to keep the current code?
>>   
>>> I saw that your change to ssd130x also uses the pattern. If we find more
>>> such drivers, we could implement the atomic check as a helper. I suggest
>>> drm_plane_helper_atomic_check_fixed() in drm_plane_helper.c
>>>
>>
>> Sure. I can add a preparatory change in v2 that adds that helper and then
>> use it in the follow-up patch.
>>
> 
> Maybe wait for your ssd130x changes to land and then you can convert 
> both drivers to the new helper.
> 

Makes sense. I'll do that.

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat