[PATCH v2 1/2] drm/gem: Export helpers for shadow-buffered planes
Thomas Zimmermann
tzimmermann at suse.de
Tue Feb 9 12:04:14 UTC 2021
Hi
Am 09.02.21 um 10:44 schrieb Daniel Vetter:
> On Mon, Feb 08, 2021 at 02:50:43PM +0100, Thomas Zimmermann wrote:
>> Export the helpers for shadow-buffered planes. These will be used by
>> several drivers.
>>
>> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
>> ---
>> drivers/gpu/drm/drm_gem_atomic_helper.c | 148 +++++++++++++++++++++++-
>> include/drm/drm_gem_atomic_helper.h | 32 +++++
>> 2 files changed, 174 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_gem_atomic_helper.c b/drivers/gpu/drm/drm_gem_atomic_helper.c
>> index e27762cef360..79b4d3f0495a 100644
>> --- a/drivers/gpu/drm/drm_gem_atomic_helper.c
>> +++ b/drivers/gpu/drm/drm_gem_atomic_helper.c
>> @@ -14,13 +14,101 @@
>> * functions for drivers that use GEM objects. Currently, it provides
>> * plane state and framebuffer BO mappings for planes with shadow
>> * buffers.
>> + *
>> + * A driver using a shadow buffer copies the content of the shadow buffers
>> + * into the HW's framebuffer memory during an atomic update. This requires
>> + * a mapping of the shadow buffer into kernel address space. The mappings
>> + * cannot be established by commit-tail functions, such as atomic_update,
>> + * as this would violate locking rules vmap.
>
> "... locking rules around dma_buf_vmap()"?
>
>> + *
>> + * The helpers for shadow-buffered planes establish and release mappings,
>> + * and provide struct drm_shadow_plane_state, which stores the plane's mapping
>> + * for commit-tail functons.
>> + *
>> + * Shadow-buffered planes can easily be enabled by using the provided macros
>> + * DRM_GEM_PLANE_SHADOW_FUNCS and DRM_GEM_SHADOE_PLANE_HELPER_FUNCS.
>
> I think for hyperlinks/highlights we need %CONSTANT? Maybe check what works.
>
>> + * These macros set up the plane and plane-helper callbacks to point to the
>> + * shadow-buffer helpers.
>> + *
>> + * .. code-block:: c
>> + *
>> + * #include <drm/drm/gem_atomic_helper.h>
>> + *
>> + * struct drm_plane_funcs driver_plane_funcs = {
>> + * ...,
>> + * DRM_GEM_SHADOW_PLANE_FUNCS,
>> + * };
>> + *
>> + * struct drm_plane_helper_funcs driver_plane_helper_funcs = {
>> + * ...,
>> + * DRM_GEM_SHADOW_PLANE_HELPER_FUNCS,
>> + * };
>> + *
>> + * In the driver's atomic-update function, shadow-buffer mappings are available
>> + * from the plane state. Use to_drm_shadow_plane_state() to upcast from
>> + * struct drm_plane_state.
>> + *
>> + * .. code-block:: c
>> + *
>> + * void driver_plane_atomic_update(struct drm_plane *plane,
>> + * struct drm_plane_state *old_plane_state)
>> + * {
>> + * struct drm_plane_state *plane_state = plane->state;
>> + * struct drm_shadow_plane_state *shadow_plane_state =
>> + * to_drm_shadow_plane_state(plane_state);
>> + *
>> + * // access shadow buffer via shadow_plane_state->map
>> + * }
>> + *
>> + * A mapping address for each of the framebuffer's buffer object is stored in
>> + * struct drm_shadow_plane_state.map. The mappings are valid while the state
>> + * is being used.
>> + *
>> + * Drivers that use struct drm_simple_display_pipe can use
>> + * DRM_GEM_SIMPLE_DISPLAY_PIPE_SHADOW_PLANE_FUNCS to initialize the rsp
>> + * callbacks. Access to shadow-buffer mappings is similar to regular
>> + * atomic_update.
>> + *
>> + * .. code-block:: c
>> + *
>> + * struct drm_simple_display_pipe_funcs driver_pipe_funcs = {
>> + * ...,
>> + * DRM_GEM_SIMPLE_DISPLAY_PIPE_SHADOW_PLANE_FUNCS,
>> + * };
>> + *
>> + * void driver_pipe_enable(struct drm_simple_display_pipe *pipe,
>> + * struct drm_crtc_state *crtc_state,
>> + * struct drm_plane_state *plane_state)
>> + * {
>> + * struct drm_shadow_plane_state *shadow_plane_state =
>> + * to_drm_shadow_plane_state(plane_state);
>> + *
>> + * // access shadow buffer via shadow_plane_state->map
>> + * }
>> */
>>
>> /*
>> * Shadow-buffered Planes
>> */
>>
>> -static struct drm_plane_state *
>> +/**
>> + * drm_gem_duplicate_shadow_plane_state - duplicates shadow-buffered plane state
>> + * @plane: the plane
>> + *
>> + * This function implements struct drm_plane_funcs.atomic_duplicate_state for
>
> Does this hyperlink automatically? I didn't know it works since for
> members I just always use &struct.member myself.
Ah, ok. Fixed. This work with struct &name.field. The % only adds
formatting to constants.
Best regards
Thomas
>
>> + * shadow-buffered planes. It assumes the existing state to be of type
>> + * struct drm_shadow_plane_state and it allocates the new state to be of this
>> + * type.
>> + *
>> + * The function does not duplicate existing mappings of the shadow buffers.
>> + * Mappings are maintained during the atomic commit by the plane's prepare_fb
>> + * and cleanup_fb helpers. See drm_gem_prepare_shadow_fb() and drm_gem_cleanup_shadow_fb()
>> + * for corresponding helpers.
>> + *
>> + * Returns:
>> + * A pointer to a new plane state on success, or NULL otherwise.
>> + */
>> +struct drm_plane_state *
>> drm_gem_duplicate_shadow_plane_state(struct drm_plane *plane)
>> {
>> struct drm_plane_state *plane_state = plane->state;
>> @@ -36,9 +124,19 @@ drm_gem_duplicate_shadow_plane_state(struct drm_plane *plane)
>>
>> return &new_shadow_plane_state->base;
>> }
>> +EXPORT_SYMBOL(drm_gem_duplicate_shadow_plane_state);
>>
>> -static void drm_gem_destroy_shadow_plane_state(struct drm_plane *plane,
>> - struct drm_plane_state *plane_state)
>> +/**
>> + * drm_gem_destroy_shadow_plane_state - deletes shadow-buffered plane state
>> + * @plane: the plane
>> + * @plane_state: the plane state of type struct drm_shadow_plane_state
>> + *
>> + * This function implements struct drm_plane_funcs.atomic_destroy_state
>> + * for shadow-buffered planes. It expects that mappings of shadow buffers
>> + * have been released already.
>> + */
>> +void drm_gem_destroy_shadow_plane_state(struct drm_plane *plane,
>> + struct drm_plane_state *plane_state)
>> {
>> struct drm_shadow_plane_state *shadow_plane_state =
>> to_drm_shadow_plane_state(plane_state);
>> @@ -46,8 +144,18 @@ static void drm_gem_destroy_shadow_plane_state(struct drm_plane *plane,
>> __drm_atomic_helper_plane_destroy_state(&shadow_plane_state->base);
>> kfree(shadow_plane_state);
>> }
>> +EXPORT_SYMBOL(drm_gem_destroy_shadow_plane_state);
>>
>> -static void drm_gem_reset_shadow_plane(struct drm_plane *plane)
>> +/**
>> + * drm_gem_reset_shadow_plane - resets a shadow-buffered plane
>> + * @plane: the plane
>> + *
>> + * This function implements struct drm_plane_funcs.reset_plane for
>> + * shadow-buffered planes. It assumes the current plane state to be
>> + * of type struct drm_shadow_plane and it allocates the new state of
>> + * this type.
>> + */
>> +void drm_gem_reset_shadow_plane(struct drm_plane *plane)
>> {
>> struct drm_shadow_plane_state *shadow_plane_state;
>>
>> @@ -61,8 +169,24 @@ static void drm_gem_reset_shadow_plane(struct drm_plane *plane)
>> return;
>> __drm_atomic_helper_plane_reset(plane, &shadow_plane_state->base);
>> }
>> +EXPORT_SYMBOL(drm_gem_reset_shadow_plane);
>>
>> -static int drm_gem_prepare_shadow_fb(struct drm_plane *plane, struct drm_plane_state *plane_state)
>> +/**
>> + * drm_gem_prepare_shadow_fb - prepares shadow framebuffers
>> + * @plane: the plane
>> + * @plane_state: the plane state of type struct drm_shadow_plane_state
>> + *
>> + * This function implements struct drm_plane_helper_funcs.prepare_fb. It
>> + * maps all buffer objects of the plane's framebuffer into kernel address
>> + * space and stores them in struct drm_shadow_plane_state.map. The
>> + * framebuffer will be synchronized as part of the atomic commit.
>> + *
>> + * See drm_gem_cleanup_shadow_fb() for cleanup.
>> + *
>> + * Returns:
>> + * 0 on success, or a negative errno code otherwise.
>> + */
>> +int drm_gem_prepare_shadow_fb(struct drm_plane *plane, struct drm_plane_state *plane_state)
>> {
>> struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(plane_state);
>> struct drm_framebuffer *fb = plane_state->fb;
>> @@ -100,8 +224,19 @@ static int drm_gem_prepare_shadow_fb(struct drm_plane *plane, struct drm_plane_s
>> }
>> return ret;
>> }
>> +EXPORT_SYMBOL(drm_gem_prepare_shadow_fb);
>>
>> -static void drm_gem_cleanup_shadow_fb(struct drm_plane *plane, struct drm_plane_state *plane_state)
>> +/**
>> + * drm_gem_cleanup_shadow_fb - releases shadow framebuffers
>> + * @plane: the plane
>> + * @plane_state: the plane state of type struct drm_shadow_plane_state
>> + *
>> + * This function implements struct drm_plane_helper_funcs.cleanup_fb.
>> + * This function unmaps all buffer objects of the plane's framebuffer.
>> + *
>> + * See drm_gem_prepare_shadow_fb() for more inforamtion.
>> + */
>> +void drm_gem_cleanup_shadow_fb(struct drm_plane *plane, struct drm_plane_state *plane_state)
>> {
>> struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(plane_state);
>> struct drm_framebuffer *fb = plane_state->fb;
>> @@ -119,6 +254,7 @@ static void drm_gem_cleanup_shadow_fb(struct drm_plane *plane, struct drm_plane_
>> drm_gem_vunmap(obj, &shadow_plane_state->map[i]);
>> }
>> }
>> +EXPORT_SYMBOL(drm_gem_cleanup_shadow_fb);
>>
>> /**
>> * drm_gem_simple_kms_prepare_shadow_fb - prepares shadow framebuffers
>> diff --git a/include/drm/drm_gem_atomic_helper.h b/include/drm/drm_gem_atomic_helper.h
>> index 08b96ccea325..7abf40bdab3d 100644
>> --- a/include/drm/drm_gem_atomic_helper.h
>> +++ b/include/drm/drm_gem_atomic_helper.h
>> @@ -45,6 +45,38 @@ to_drm_shadow_plane_state(struct drm_plane_state *state)
>> return container_of(state, struct drm_shadow_plane_state, base);
>> }
>>
>> +void drm_gem_reset_shadow_plane(struct drm_plane *plane);
>> +struct drm_plane_state *drm_gem_duplicate_shadow_plane_state(struct drm_plane *plane);
>> +void drm_gem_destroy_shadow_plane_state(struct drm_plane *plane,
>> + struct drm_plane_state *plane_state);
>> +
>> +/**
>> + * DRM_GEM_SHADOW_PLANE_FUNCS -
>> + * Initializes struct drm_plane_funcs for shadow-buffered planes
>> + *
>> + * Drivers may use GEM BOs as shadow buffers over the framebuffer memory. This
>> + * macro initializes struct drm_plane_funcs to use the rsp helper functions.
>> + */
>> +#define DRM_GEM_SHADOW_PLANE_FUNCS \
>> + .reset = drm_gem_reset_shadow_plane, \
>> + .atomic_duplicate_state = drm_gem_duplicate_shadow_plane_state, \
>> + .atomic_destroy_state = drm_gem_destroy_shadow_plane_state
>> +
>> +int drm_gem_prepare_shadow_fb(struct drm_plane *plane, struct drm_plane_state *plane_state);
>> +void drm_gem_cleanup_shadow_fb(struct drm_plane *plane, struct drm_plane_state *plane_state);
>> +
>> +/**
>> + * DRM_GEM_SHADOW_PLANE_HELPER_FUNCS -
>> + * Initializes struct drm_plane_helper_funcs for shadow-buffered planes
>> + *
>> + * Drivers may use GEM BOs as shadow buffers over the framebuffer memory. This
>> + * macro initializes struct drm_plane_helper_funcs to use the rsp helper
>> + * functions.
>> + */
>> +#define DRM_GEM_SHADOW_PLANE_HELPER_FUNCS \
>> + .prepare_fb = drm_gem_prepare_shadow_fb, \
>> + .cleanup_fb = drm_gem_cleanup_shadow_fb
>> +
>> int drm_gem_simple_kms_prepare_shadow_fb(struct drm_simple_display_pipe *pipe,
>> struct drm_plane_state *plane_state);
>> void drm_gem_simple_kms_cleanup_shadow_fb(struct drm_simple_display_pipe *pipe,
>
>
> Very nice and thoroughly explained docs!
>
> Thanks, Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
>
>> --
>> 2.30.0
>>
>
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer
-------------- next part --------------
A non-text attachment was scrubbed...
Name: OpenPGP_signature
Type: application/pgp-signature
Size: 840 bytes
Desc: OpenPGP digital signature
URL: <https://lists.freedesktop.org/archives/dri-devel/attachments/20210209/31de5800/attachment.sig>
More information about the dri-devel
mailing list