Add documentation around vkms_output and its initialization. Signed-off-by: Louis Chauvet <louis.chauvet@xxxxxxxxxxx> --- This series does not introduce functionnal changes, only some documentation and renaming to clarify the code. --- Changes in v2: - Dropped already applied patches - Dropped useless patch as its content is deleted later - Remove dependency on previous series - Apply Maíra's comments - Link to v1: https://lore.kernel.org/r/20240814-google-clarifications-v1-0-3ee76d7d0c28@xxxxxxxxxxx --- drivers/gpu/drm/vkms/vkms_drv.h | 86 ++++++++++++++++++++++++++++++++------ drivers/gpu/drm/vkms/vkms_output.c | 12 ++++++ 2 files changed, 86 insertions(+), 12 deletions(-) diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h index 5e46ea5b96dc..1fc068d4de4c 100644 --- a/drivers/gpu/drm/vkms/vkms_drv.h +++ b/drivers/gpu/drm/vkms/vkms_drv.h @@ -73,29 +73,56 @@ struct vkms_color_lut { }; /** - * vkms_crtc_state - Driver specific CRTC state + * struct vkms_crtc_state - Driver specific CRTC state + * * @base: base CRTC state * @composer_work: work struct to compose and add CRC entries - * @n_frame_start: start frame number for computed CRC - * @n_frame_end: end frame number for computed CRC + * + * @num_active_planes: Number of active planes + * @active_planes: List containing all the active planes (counted by + * @num_active_planes). They should be stored in z-order. + * @active_writeback: Current active writeback job + * @gamma_lut: Look up table for gamma used in this CRTC + * @crc_pending: Protected by @vkms_output.composer_lock, true when the frame CRC is not computed + * yet. Used by vblank to detect if the composer is too slow. + * @wb_pending: Protected by @vkms_output.composer_lock, true when a writeback frame is requested. + * @frame_start: Protected by @vkms_output.composer_lock, saves the frame number before the start + * of the composition process. + * @frame_end: Protected by @vkms_output.composer_lock, saves the last requested frame number. + * This is used to generate enough CRC entries when the composition worker is too slow. */ struct vkms_crtc_state { struct drm_crtc_state base; struct work_struct composer_work; int num_active_planes; - /* stack of active planes for crc computation, should be in z order */ struct vkms_plane_state **active_planes; struct vkms_writeback_job *active_writeback; struct vkms_color_lut gamma_lut; - /* below four are protected by vkms_output.composer_lock */ bool crc_pending; bool wb_pending; u64 frame_start; u64 frame_end; }; +/** + * struct vkms_output - Internal representation of all output components in vkms + * + * @crtc: Base CRTC in DRM + * @encoder: DRM encoder used for this output + * @connector: DRM connector used for this output + * @wb_connecter: DRM writeback connector used for this output + * @vblank_hrtimer: Timer used to trigger the vblank + * @period_ns: Period of the vblank timer, used to configure @vblank_hrtimer and to compute + * vblank timestamps + * @composer_workq: Ordered workqueue for @composer_state.composer_work. + * @lock: Lock used to protect concurrent access to the composer + * @composer_enabled: Protected by @lock, true when the vkms composer is active (crc needed or + * writeback) + * @composer_state: Current state of this vkms output + * @composer_lock: Lock used internally to protect @composer_state members + */ struct vkms_output { struct drm_crtc crtc; struct drm_encoder encoder; @@ -103,28 +130,38 @@ struct vkms_output { struct drm_writeback_connector wb_connector; struct hrtimer vblank_hrtimer; ktime_t period_ns; - /* ordered wq for composer_work */ struct workqueue_struct *composer_workq; - /* protects concurrent access to composer */ spinlock_t lock; - /* protected by @lock */ bool composer_enabled; struct vkms_crtc_state *composer_state; spinlock_t composer_lock; }; -struct vkms_device; - +/** + * struct vkms_config - General configuration for VKMS driver + * + * @writeback: If true, a writeback buffer can be attached to the CRTC + * @cursor: If true, a cursor plane is created in the VKMS device + * @overlay: If true, NUM_OVERLAY_PLANES will be created for the VKMS device + * @dev: Used to store the current vkms device. Only set when the device is instantiated. + */ struct vkms_config { bool writeback; bool cursor; bool overlay; - /* only set when instantiated */ struct vkms_device *dev; }; +/** + * struct vkms_device - Description of a vkms device + * + * @drm - Base device in DRM + * @platform - Associated platform device + * @output - Configuration and sub-components of the vkms device + * @config: Configuration used in this vkms device + */ struct vkms_device { struct drm_device drm; struct platform_device *platform; @@ -132,6 +169,10 @@ struct vkms_device { const struct vkms_config *config; }; +/* + * The following helpers are used to convert a member of a struct into its parent. + */ + #define drm_crtc_to_vkms_output(target) \ container_of(target, struct vkms_output, crtc) @@ -144,12 +185,33 @@ struct vkms_device { #define to_vkms_plane_state(target)\ container_of(target, struct vkms_plane_state, base.base) -/* CRTC */ +/** + * vkms_crtc_init() - Initialize a CRTC for vkms + * @dev: DRM device associated with the vkms buffer + * @crtc: uninitialized CRTC device + * @primary: primary plane to attach to the CRTC + * @cursor plane to attach to the CRTC + */ int vkms_crtc_init(struct drm_device *dev, struct drm_crtc *crtc, struct drm_plane *primary, struct drm_plane *cursor); +/** + * vkms_output_init() - Initialize all sub-components needed for a vkms device. + * + * @vkmsdev: vkms device to initialize + * @possible_crtc_index: CRTC which can be attached to the planes. The caller must ensure that + * possible_crtc_index is positive and less or equals to 31. + */ int vkms_output_init(struct vkms_device *vkmsdev, int index); +/** + * vkms_plane_init() - Initialize a plane + * + * @vkmsdev: vkms device containing the plane + * @type: type of plane to initialize + * @possible_crtc_index: CRTC which can be attached to the plane. The caller must ensure that + * possible_crtc_index is positive and less or equals to 31. + */ struct vkms_plane *vkms_plane_init(struct vkms_device *vkmsdev, enum drm_plane_type type, int index); diff --git a/drivers/gpu/drm/vkms/vkms_output.c b/drivers/gpu/drm/vkms/vkms_output.c index 5ce70dd946aa..da69beb43ab0 100644 --- a/drivers/gpu/drm/vkms/vkms_output.c +++ b/drivers/gpu/drm/vkms/vkms_output.c @@ -21,6 +21,7 @@ static int vkms_conn_get_modes(struct drm_connector *connector) { int count; + /* Use the default modes list from DRM */ count = drm_add_modes_noedid(connector, XRES_MAX, YRES_MAX); drm_set_preferred_mode(connector, XRES_DEF, YRES_DEF); @@ -58,6 +59,12 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index) int writeback; unsigned int n; + /* + * Initialize used plane. One primary plane is required to perform the composition. + * + * The overlay and cursor planes are not mandatory, but can be used to perform complex + * composition. + */ primary = vkms_plane_init(vkmsdev, DRM_PLANE_TYPE_PRIMARY, index); if (IS_ERR(primary)) return PTR_ERR(primary); @@ -76,6 +83,7 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index) return PTR_ERR(cursor); } + /* [1]: Allocation of a CRTC, its index will be 1 */ ret = vkms_crtc_init(dev, crtc, &primary->base, &cursor->base); if (ret) return ret; @@ -95,6 +103,10 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index) DRM_ERROR("Failed to init encoder\n"); goto err_encoder; } + /* + * This is an hardcoded value to select crtc for the encoder. + * 1 here designate the first registered CRTC, the one allocated in [1] + */ encoder->possible_crtcs = 1; ret = drm_connector_attach_encoder(connector, encoder); --- base-commit: 22bc22ccf95bfa6eb6288ba4bc33d7fc0078381e change-id: 20240520-google-clarifications-dede8dcbe38a Best regards, -- Louis Chauvet <louis.chauvet@xxxxxxxxxxx>
