Hi Louis, Thanks for appling the suggested changes. I added some minor style comments, but other than that patch looks good to me. > Add documentation around vkms_output and its initialization. > Add some documentation on pixel conversion functions. > Update of outdated comments for pixel_write functions. > > Signed-off-by: Louis Chauvet <louis.chauvet@xxxxxxxxxxx> With the suggested changes, feel free to add: Reviewed-by: José Expósito <jose.exposito89@xxxxxxxxx> > --- > This series does not introduce functionnal changes, only some > documentation and renaming to clarify the code. > --- > Changes in v3: > - Merged https://lore.kernel.org/all/20240802-yuv-v9-3-08a706669e16@xxxxxxxxxxx/ > as it also add documentation > - Apply José's comments, sorry > - Replace =1 by =BIT(0) for possible_crtc value > - Link to v2: https://lore.kernel.org/r/20240826-google-clarifications-v2-1-2574655b0b91@xxxxxxxxxxx > > 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_composer.c | 7 +++ > drivers/gpu/drm/vkms/vkms_drv.h | 101 ++++++++++++++++++++++++++++++----- > drivers/gpu/drm/vkms/vkms_formats.c | 62 +++++++++++++++++---- > drivers/gpu/drm/vkms/vkms_output.c | 14 ++++- > 4 files changed, 161 insertions(+), 23 deletions(-) > > > --- > base-commit: 84addde447fd9d713e101437db0d4924855eff4f > change-id: 20240520-google-clarifications-dede8dcbe38a > > Best regards, > > diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c > index e7441b227b3c..57a5769fc994 100644 > --- a/drivers/gpu/drm/vkms/vkms_composer.c > +++ b/drivers/gpu/drm/vkms/vkms_composer.c > @@ -189,6 +189,13 @@ static void blend(struct vkms_writeback_job *wb, > > size_t crtc_y_limit = crtc_state->base.crtc->mode.vdisplay; > > + /* > + * The planes are composed line-by-line to avoid heavy memory usage. It is a necessary > + * complexity to avoid poor blending performance. > + * > + * The function vkms_compose_row() is used to read a line, pixel-by-pixel, into the staging > + * buffer. > + */ > for (size_t y = 0; y < crtc_y_limit; y++) { > fill_background(&background_color, output_buffer); > > diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h > index 5e46ea5b96dc..12a11976f2fc 100644 > --- a/drivers/gpu/drm/vkms/vkms_drv.h > +++ b/drivers/gpu/drm/vkms/vkms_drv.h > @@ -25,6 +25,17 @@ > > #define VKMS_LUT_SIZE 256 > > +/** > + * struct vkms_frame_info - Structure to store the state of a frame > + * > + * @fb: backing drm framebuffer > + * @src: source rectangle of this frame in the source framebuffer, stored in 16.16 fixed-point form > + * @dst: destination rectangle in the crtc buffer, stored in whole pixel units > + * @map: see drm_shadow_plane_state@data I think that the right format is "@drm_shadow_plane_state.data"? https://docs.kernel.org/doc-guide/kernel-doc.html#nested-structs-unions > + * @rotation: rotation applied to the source. > + * > + * @src and @dst should have the same size modulo the rotation. > + */ > struct vkms_frame_info { > struct drm_framebuffer *fb; > struct drm_rect src, dst; > @@ -52,9 +63,11 @@ struct vkms_writeback_job { > }; > > /** > - * vkms_plane_state - Driver specific plane state > + * struct vkms_plane_state - Driver specific plane state > * @base: base plane state > * @frame_info: data required for composing computation > + * @pixel_read: function to read a pixel in this plane. The creator of a struct vkms_plane_state > + * must ensure that this pointer is valid > */ > struct vkms_plane_state { > struct drm_shadow_plane_state base; > @@ -73,29 +86,56 @@ 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 > + * Sorry I missed this extra empty line in my previous review. You can delete this extra "*". > + * @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: vblank period, in nanoseconds, 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: Protected by @lock, 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 +143,38 @@ 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 +182,10 @@ 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 +198,33 @@ 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 Missing ":" after "@cursor": * @cursor: 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 > + * @index: CRTC which can be attached to the planes. The caller must ensure that > + * @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. Should read: * @index: CRTC which can be attached to the plane. The caller must ensure that * @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_formats.c b/drivers/gpu/drm/vkms/vkms_formats.c > index 040b7f113a3b..e8a5cc235ebb 100644 > --- a/drivers/gpu/drm/vkms/vkms_formats.c > +++ b/drivers/gpu/drm/vkms/vkms_formats.c > @@ -9,24 +9,40 @@ > > #include "vkms_formats.h" > > +/** > + * pixel_offset() - Get the offset of the pixel at coordinates x/y in the first plane > + * > + * @frame_info: Buffer metadata > + * @x: The x coordinate of the wanted pixel in the buffer > + * @y: The y coordinate of the wanted pixel in the buffer > + * > + * The caller must ensure that the framebuffer associated with this request uses a pixel format > + * where block_h == block_w == 1. > + * If this requirement is not fulfilled, the resulting offset can point to an other pixel or > + * outside of the buffer. > + */ > static size_t pixel_offset(const struct vkms_frame_info *frame_info, int x, int y) > { > return frame_info->offset + (y * frame_info->pitch) > + (x * frame_info->cpp); > } > > -/* > - * packed_pixels_addr - Get the pointer to pixel of a given pair of coordinates > +/** > + * packed_pixels_addr() - Get the pointer to the block containing the pixel at the given > + * coordinates > * > * @frame_info: Buffer metadata > - * @x: The x(width) coordinate of the 2D buffer > - * @y: The y(Heigth) coordinate of the 2D buffer > + * @x: The x (width) coordinate inside the plane > + * @y: The y (height) coordinate inside the plane > * > * Takes the information stored in the frame_info, a pair of coordinates, and > * returns the address of the first color channel. > * This function assumes the channels are packed together, i.e. a color channel > * comes immediately after another in the memory. And therefore, this function > * doesn't work for YUV with chroma subsampling (e.g. YUV420 and NV21). > + * > + * The caller must ensure that the framebuffer associated with this request uses a pixel format > + * where block_h == block_w == 1, otherwise the returned pointer can be outside the buffer. > */ > static void *packed_pixels_addr(const struct vkms_frame_info *frame_info, > int x, int y) > @@ -51,6 +67,13 @@ static int get_x_position(const struct vkms_frame_info *frame_info, int limit, i > return x; > } > > +/* > + * The following functions take pixel data from the buffer and convert them to the format > + * ARGB16161616 in @out_pixel. > + * > + * They are used in the vkms_compose_row() function to handle multiple formats. > + */ > + > static void ARGB8888_to_argb_u16(u8 *src_pixels, struct pixel_argb_u16 *out_pixel) > { > /* > @@ -143,12 +166,11 @@ void vkms_compose_row(struct line_buffer *stage_buffer, struct vkms_plane_state > } > > /* > - * The following functions take an line of argb_u16 pixels from the > - * src_buffer, convert them to a specific format, and store them in the > - * destination. > + * The following functions take one &struct pixel_argb_u16 and convert it to a specific format. > + * The result is stored in @dst_pixels. > * > - * They are used in the `compose_active_planes` to convert and store a line > - * from the src_buffer to the writeback buffer. > + * They are used in vkms_writeback_row() to convert and store a pixel from the src_buffer to > + * the writeback buffer. > */ > static void argb_u16_to_ARGB8888(u8 *dst_pixels, struct pixel_argb_u16 *in_pixel) > { > @@ -214,6 +236,14 @@ static void argb_u16_to_RGB565(u8 *dst_pixels, struct pixel_argb_u16 *in_pixel) > *pixels = cpu_to_le16(r << 11 | g << 5 | b); > } > > +/** > + * vkms_writeback_row() - Generic loop for all supported writeback format. It is executed just > + * after the blending to write a line in the writeback buffer. > + * > + * @wb: Job where to insert the final image > + * @src_buffer: Line to write > + * @y: Row to write in the writeback buffer > + */ > void vkms_writeback_row(struct vkms_writeback_job *wb, > const struct line_buffer *src_buffer, int y) > { > @@ -227,6 +257,13 @@ void vkms_writeback_row(struct vkms_writeback_job *wb, > wb->pixel_write(dst_pixels, &in_pixels[x]); > } > > +/** > + * get_pixel_conversion_function() - Retrieve the correct read_pixel function for a specific > + * format. The returned pointer is NULL for unsupported pixel formats. The caller must ensure that > + * the pointer is valid before using it in a vkms_plane_state. > + * > + * @format: DRM_FORMAT_* value for which to obtain a conversion function (see [drm_fourcc.h]) > + */ > void *get_pixel_conversion_function(u32 format) > { > switch (format) { > @@ -245,6 +282,13 @@ void *get_pixel_conversion_function(u32 format) > } > } > > +/** > + * get_pixel_write_function() - Retrieve the correct write_pixel function for a specific format. > + * The returned pointer is NULL for unsupported pixel formats. The caller must ensure that the > + * pointer is valid before using it in a vkms_writeback_job. > + * > + * @format: DRM_FORMAT_* value for which to obtain a conversion function (see [drm_fourcc.h]) > + */ > void *get_pixel_write_function(u32 format) > { > switch (format) { > diff --git a/drivers/gpu/drm/vkms/vkms_output.c b/drivers/gpu/drm/vkms/vkms_output.c > index 5ce70dd946aa..56801e914208 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 */ It'd be great to clarify that BIT(0) == 1. Maybe? /* [1]: Allocation of a CRTC, its index will be BIT(0) = 1 */ > ret = vkms_crtc_init(dev, crtc, &primary->base, &cursor->base); > if (ret) > return ret; > @@ -95,7 +103,11 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index) > DRM_ERROR("Failed to init encoder\n"); > goto err_encoder; > } > - encoder->possible_crtcs = 1; > + /* > + * This is a hardcoded value to select crtc for the encoder. > + * 1 here designate the first registered CRTC, the one allocated in [1] BIT(0) here designate the first... > + */ > + encoder->possible_crtcs = BIT(0); > > ret = drm_connector_attach_encoder(connector, encoder); > if (ret) {
