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Message-ID: <4002a4d6-04cb-b342-952f-b42ef3188df4@suse.de>
Date: Mon, 12 Sep 2022 14:05:36 +0200
From: Thomas Zimmermann <tzimmermann@...e.de>
To: Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc: David Airlie <airlied@...ux.ie>,
Javier Martinez Canillas <javierm@...hat.com>,
dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/plane-helper: Add a drm_plane_helper_atomic_check()
helper
Hi
Am 12.09.22 um 13:18 schrieb Ville Syrjälä:
> On Mon, Sep 12, 2022 at 01:05:45PM +0200, Thomas Zimmermann wrote:
>> Hi
>>
>> Am 12.09.22 um 12:40 schrieb Ville Syrjälä:
>>> On Mon, Sep 12, 2022 at 12:15:22PM +0200, Javier Martinez Canillas wrote:
>>>> Provides a default plane state check handler for primary planes that are a
>>>> fullscreen scanout buffer and whose state scale and position can't change.
>>>>
>>>> There are some drivers that duplicate this logic in their helpers, such as
>>>> simpledrm and ssd130x. Factor out this common code into a plane helper and
>>>> make drivers use it.
>>>>
>>>> Suggested-by: Thomas Zimmermann <tzimmermann@...e.de>
>>>> Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
>>>> ---
>>>>
>>>> drivers/gpu/drm/drm_plane_helper.c | 29 +++++++++++++++++++++++++++++
>>>> drivers/gpu/drm/solomon/ssd130x.c | 18 +-----------------
>>>> drivers/gpu/drm/tiny/simpledrm.c | 25 +------------------------
>>>> include/drm/drm_plane_helper.h | 2 ++
>>>> 4 files changed, 33 insertions(+), 41 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/drm_plane_helper.c b/drivers/gpu/drm/drm_plane_helper.c
>>>> index c7785967f5bf..fb41eee74693 100644
>>>> --- a/drivers/gpu/drm/drm_plane_helper.c
>>>> +++ b/drivers/gpu/drm/drm_plane_helper.c
>>>> @@ -278,3 +278,32 @@ void drm_plane_helper_destroy(struct drm_plane *plane)
>>>> kfree(plane);
>>>> }
>>>> EXPORT_SYMBOL(drm_plane_helper_destroy);
>>>> +
>>>> +/**
>>>> + * drm_plane_helper_atomic_check() - Helper to check primary planes states
>>>> + * @plane: plane to check
>>>> + * @new_state: plane state to check
>>>
>>> That is not a plane state. Also should s/new_// since it's just
>>> the overall atomic state thing rather than some new or old state.
>>
>> Using only 'state' is non-intuitive and has lead to bugs where sub-state
>> was retrieved from the wrong state information. So we've been using
>> 'new_state' and 'old_state' explicitly in several places now.
>
> There is no old or new drm_atomic_state. It contains both.
I (vaguely) remember a bug where a driver tried
drm_atomic_get_new_plane_state() with the (old) state that's passed to
atomic_update. It didn't return the expected results and modesetting
gave slightly wrong results. So we began to be more precise about new
and old. And whatever is stored in 'plane->state' is then just 'the state'.
I understand that the semantics of atomic_check are different from
atomic_update, but it still doesn't hurt to talk of new_state IMHO.
Best regards
Thomas
>
>>
>> Best regards
>> Thomas
>>
>>>
>>>> + *
>>>> + * Provides a default plane state check handler for primary planes whose atomic
>>>> + * state scale and position is not expected to change because the primary plane
>>>> + * is always a fullscreen scanout buffer.
>>>> + *
>>>> + * RETURNS:
>>>> + * Zero on success, or an errno code otherwise.
>>>> + */
>>>> +int drm_plane_helper_atomic_check(struct drm_plane *plane,
>>>> + struct drm_atomic_state *new_state)
>>>> +{
>>>> + 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;
>>>> +
>>>> + if (new_crtc)
>>>> + new_crtc_state = drm_atomic_get_new_crtc_state(new_state, new_crtc);
>>>> +
>>>> + return drm_atomic_helper_check_plane_state(new_plane_state, new_crtc_state,
>>>> + DRM_PLANE_NO_SCALING,
>>>> + DRM_PLANE_NO_SCALING,
>>>> + false, false);
>>>> +}
>>>> +EXPORT_SYMBOL(drm_plane_helper_atomic_check);
>>>> diff --git a/drivers/gpu/drm/solomon/ssd130x.c b/drivers/gpu/drm/solomon/ssd130x.c
>>>> index 79e8e2017c68..28cf9c87f86d 100644
>>>> --- a/drivers/gpu/drm/solomon/ssd130x.c
>>>> +++ b/drivers/gpu/drm/solomon/ssd130x.c
>>>> @@ -565,22 +565,6 @@ static int ssd130x_fb_blit_rect(struct drm_framebuffer *fb, const struct iosys_m
>>>> return ret;
>>>> }
>>>>
>>>> -static int ssd130x_primary_plane_helper_atomic_check(struct drm_plane *plane,
>>>> - struct drm_atomic_state *new_state)
>>>> -{
>>>> - 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;
>>>> -
>>>> - if (new_crtc)
>>>> - new_crtc_state = drm_atomic_get_new_crtc_state(new_state, new_crtc);
>>>> -
>>>> - 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 ssd130x_primary_plane_helper_atomic_update(struct drm_plane *plane,
>>>> struct drm_atomic_state *old_state)
>>>> {
>>>> @@ -623,7 +607,7 @@ static void ssd130x_primary_plane_helper_atomic_disable(struct drm_plane *plane,
>>>>
>>>> static const struct drm_plane_helper_funcs ssd130x_primary_plane_helper_funcs = {
>>>> DRM_GEM_SHADOW_PLANE_HELPER_FUNCS,
>>>> - .atomic_check = ssd130x_primary_plane_helper_atomic_check,
>>>> + .atomic_check = drm_plane_helper_atomic_check,
>>>> .atomic_update = ssd130x_primary_plane_helper_atomic_update,
>>>> .atomic_disable = ssd130x_primary_plane_helper_atomic_disable,
>>>> };
>>>> diff --git a/drivers/gpu/drm/tiny/simpledrm.c b/drivers/gpu/drm/tiny/simpledrm.c
>>>> index 777ccd250871..ea5b3239a659 100644
>>>> --- a/drivers/gpu/drm/tiny/simpledrm.c
>>>> +++ b/drivers/gpu/drm/tiny/simpledrm.c
>>>> @@ -469,29 +469,6 @@ static const uint64_t simpledrm_primary_plane_format_modifiers[] = {
>>>> DRM_FORMAT_MOD_INVALID
>>>> };
>>>>
>>>> -static int simpledrm_primary_plane_helper_atomic_check(struct drm_plane *plane,
>>>> - struct drm_atomic_state *new_state)
>>>> -{
>>>> - 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;
>>>> -}
>>>> -
>>>> static void simpledrm_primary_plane_helper_atomic_update(struct drm_plane *plane,
>>>> struct drm_atomic_state *old_state)
>>>> {
>>>> @@ -543,7 +520,7 @@ static void simpledrm_primary_plane_helper_atomic_disable(struct drm_plane *plan
>>>>
>>>> static const struct drm_plane_helper_funcs simpledrm_primary_plane_helper_funcs = {
>>>> DRM_GEM_SHADOW_PLANE_HELPER_FUNCS,
>>>> - .atomic_check = simpledrm_primary_plane_helper_atomic_check,
>>>> + .atomic_check = drm_plane_helper_atomic_check,
>>>> .atomic_update = simpledrm_primary_plane_helper_atomic_update,
>>>> .atomic_disable = simpledrm_primary_plane_helper_atomic_disable,
>>>> };
>>>> diff --git a/include/drm/drm_plane_helper.h b/include/drm/drm_plane_helper.h
>>>> index 1781fab24dd6..7ba414655d69 100644
>>>> --- a/include/drm/drm_plane_helper.h
>>>> +++ b/include/drm/drm_plane_helper.h
>>>> @@ -41,5 +41,7 @@ int drm_plane_helper_update_primary(struct drm_plane *plane, struct drm_crtc *cr
>>>> int drm_plane_helper_disable_primary(struct drm_plane *plane,
>>>> struct drm_modeset_acquire_ctx *ctx);
>>>> void drm_plane_helper_destroy(struct drm_plane *plane);
>>>> +int drm_plane_helper_atomic_check(struct drm_plane *plane,
>>>> + struct drm_atomic_state *new_state);
>>>>
>>>> #endif
>>>> --
>>>> 2.37.1
>>>
>>
>> --
>> Thomas Zimmermann
>> Graphics Driver Developer
>> SUSE Software Solutions Germany GmbH
>> Maxfeldstr. 5, 90409 Nürnberg, Germany
>> (HRB 36809, AG Nürnberg)
>> Geschäftsführer: Ivo Totev
>
>
>
>
--
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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