drm: vkms: Add fb information to `vkms_writeback_job`

This commit is the groundwork to introduce new formats to the planes and
writeback buffer. As part of it, a new buffer metadata field is added to
`vkms_writeback_job`, this metadata is represented by the `vkms_frame_info`
struct.

Also adds two new function pointers (`line_to_frame_func` and
`frame_to_line_func`) are defined to handle format conversion
from/to internal format.

A new internal format(`struct pixel_argb_u16`) is introduced to deal with
all possible inputs. It consists of 16 bits fields that represent each of
the channels.

These things will allow us, in the future, to have different compositing
and wb format types.

V2: Change the code to get the drm_framebuffer reference and not copy its
    contents (Thomas Zimmermann).
V3: Drop the refcount in the wb code (Thomas Zimmermann).
V5: Add {wb,plane}_format_transform_func to vkms_writeback_job
    and vkms_plane_state (Pekka Paalanen)
V6: Improvements to some struct/struct members names (Pekka Paalanen).
    Splits this patch in two (Pekka Paalanen).
V7: Replace line_to_frame_func and frame_to_line_func typedefs
   with the function signature and void* (Melissa Wen).
Reviewed-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Igor Torrente <igormtorrente@gmail.com>
Signed-off-by: Melissa Wen <melissa.srw@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220905190811.25024-6-igormtorrente@gmail.com

drivers/gpu/drm/vkms/vkms_drv.h

@@ -23,11 +23,6 @@
 
 #define NUM_OVERLAY_PLANES 8
 
-struct vkms_writeback_job {
-	struct iosys_map map[DRM_FORMAT_MAX_PLANES];
-	struct iosys_map data[DRM_FORMAT_MAX_PLANES];
-};
-
 struct vkms_frame_info {
 	struct drm_framebuffer *fb;
 	struct drm_rect src, dst;
@@ -37,6 +32,22 @@ struct vkms_frame_info {
 	unsigned int cpp;
 };
 
+struct pixel_argb_u16 {
+	u16 a, r, g, b;
+};
+
+struct line_buffer {
+	size_t n_pixels;
+	struct pixel_argb_u16 *pixels;
+};
+
+struct vkms_writeback_job {
+	struct iosys_map data[DRM_FORMAT_MAX_PLANES];
+	struct vkms_frame_info wb_frame_info;
+	void (*wb_write)(struct vkms_frame_info *frame_info,
+			 const struct line_buffer *buffer, int y);
+};
+
 /**
  * vkms_plane_state - Driver specific plane state
  * @base: base plane state
@@ -45,6 +56,8 @@ struct vkms_frame_info {
 struct vkms_plane_state {
 	struct drm_shadow_plane_state base;
 	struct vkms_frame_info *frame_info;
+	void (*plane_read)(struct line_buffer *buffer,
+			   const struct vkms_frame_info *frame_info, int y);
 };
 
 struct vkms_plane {

drivers/gpu/drm/vkms/vkms_writeback.c

@@ -75,12 +75,15 @@ static int vkms_wb_prepare_job(struct drm_writeback_connector *wb_connector,
 	if (!vkmsjob)
 		return -ENOMEM;
 
-	ret = drm_gem_fb_vmap(job->fb, vkmsjob->map, vkmsjob->data);
+	ret = drm_gem_fb_vmap(job->fb, vkmsjob->wb_frame_info.map, vkmsjob->data);
 	if (ret) {
 		DRM_ERROR("vmap failed: %d\n", ret);
 		goto err_kfree;
 	}
 
+	vkmsjob->wb_frame_info.fb = job->fb;
+	drm_framebuffer_get(vkmsjob->wb_frame_info.fb);
+
 	job->priv = vkmsjob;
 
 	return 0;
@@ -99,7 +102,9 @@ static void vkms_wb_cleanup_job(struct drm_writeback_connector *connector,
 	if (!job->fb)
 		return;
 
-	drm_gem_fb_vunmap(job->fb, vkmsjob->map);
+	drm_gem_fb_vunmap(job->fb, vkmsjob->wb_frame_info.map);
+
+	drm_framebuffer_put(vkmsjob->wb_frame_info.fb);
 
 	vkmsdev = drm_device_to_vkms_device(job->fb->dev);
 	vkms_set_composer(&vkmsdev->output, false);
@@ -116,14 +121,23 @@ static void vkms_wb_atomic_commit(struct drm_connector *conn,
 	struct drm_writeback_connector *wb_conn = &output->wb_connector;
 	struct drm_connector_state *conn_state = wb_conn->base.state;
 	struct vkms_crtc_state *crtc_state = output->composer_state;
+	struct drm_framebuffer *fb = connector_state->writeback_job->fb;
+	struct vkms_writeback_job *active_wb;
+	struct vkms_frame_info *wb_frame_info;
 
 	if (!conn_state)
 		return;
 
 	vkms_set_composer(&vkmsdev->output, true);
 
+	active_wb = conn_state->writeback_job->priv;
+	wb_frame_info = &active_wb->wb_frame_info;
+
 	spin_lock_irq(&output->composer_lock);
-	crtc_state->active_writeback = conn_state->writeback_job->priv;
+	crtc_state->active_writeback = active_wb;
+	wb_frame_info->offset = fb->offsets[0];
+	wb_frame_info->pitch = fb->pitches[0];
+	wb_frame_info->cpp = fb->format->cpp[0];
 	crtc_state->wb_pending = true;
 	spin_unlock_irq(&output->composer_lock);
 	drm_writeback_queue_job(wb_conn, connector_state);