目录

1. drm_mode_setplane

1.1 根据应用的plane_req->plane_id找到plane

1.2 根据应用的plane_req->fb_id找到struct drm_framebuffer

1.3 调用setplane_internal

2. setplane_internal->__setplane_internal

2.1 struct drm_framebuffer是否为空

2.2 判断此plane是否有合适的crtc

2.3 检查plane是否支持该fb的pix format

2.4 一些越界检查

2.5 检查对齐情况

2.6 调用plane->funcs->update_plane（drm_atomic_helper_update_plane）

3. drm_atomic_helper_update_plane

3.1 drm_atomic_set_fb_for_plane 把framebuffer引用给plane

4. 流程图

---

     本文分析一下drm_mode_setplane函数。

1. drm_mode_setplane

1.1 根据应用的plane_req->plane_id找到plane

int drm_mode_setplane(struct drm_device *dev, void *data,
		      struct drm_file *file_priv)
{
	struct drm_mode_set_plane *plane_req = data;
	struct drm_plane *plane;
	struct drm_crtc *crtc = NULL;
	struct drm_framebuffer *fb = NULL;

	if (!drm_core_check_feature(dev, DRIVER_MODESET))
		return -EINVAL;

	/*
	 * First, find the plane, crtc, and fb objects.  If not available,
	 * we don't bother to call the driver.
	 */
	plane = drm_plane_find(dev, plane_req->plane_id);
	if (!plane) {
		DRM_DEBUG_KMS("Unknown plane ID %d\n",
			      plane_req->plane_id);
		return -ENOENT;
	}

1.2 根据应用的plane_req->fb_id找到struct drm_framebuffer

	if (plane_req->fb_id) {
		fb = drm_framebuffer_lookup(dev, plane_req->fb_id);
		if (!fb) {
			DRM_DEBUG_KMS("Unknown framebuffer ID %d\n",
				      plane_req->fb_id);
			return -ENOENT;
		}

		crtc = drm_crtc_find(dev, plane_req->crtc_id);
		if (!crtc) {
			drm_framebuffer_put(fb);
			DRM_DEBUG_KMS("Unknown crtc ID %d\n",
				      plane_req->crtc_id);
			return -ENOENT;
		}
	}

1.3 调用setplane_internal

	/*
	 * setplane_internal will take care of deref'ing either the old or new
	 * framebuffer depending on success.
	 */
	return setplane_internal(plane, crtc, fb,
				 plane_req->crtc_x, plane_req->crtc_y,
				 plane_req->crtc_w, plane_req->crtc_h,
				 plane_req->src_x, plane_req->src_y,
				 plane_req->src_w, plane_req->src_h);
}

2. setplane_internal->__setplane_internal

2.1 struct drm_framebuffer是否为空

static int __setplane_internal(struct drm_plane *plane,
			       struct drm_crtc *crtc,
			       struct drm_framebuffer *fb,
			       int32_t crtc_x, int32_t crtc_y,
			       uint32_t crtc_w, uint32_t crtc_h,
			       /* src_{x,y,w,h} values are 16.16 fixed point */
			       uint32_t src_x, uint32_t src_y,
			       uint32_t src_w, uint32_t src_h,
			       struct drm_modeset_acquire_ctx *ctx)
{
	int ret = 0;

	/* No fb means shut it down */
	if (!fb) {
		plane->old_fb = plane->fb;
		ret = plane->funcs->disable_plane(plane, ctx);
		if (!ret) {
			plane->crtc = NULL;
			plane->fb = NULL;
		} else {
			plane->old_fb = NULL;
		}
		goto out;
	}

2.2 判断此plane是否有合适的crtc

	/* Check whether this plane is usable on this CRTC */
	if (!(plane->possible_crtcs & drm_crtc_mask(crtc))) {
		DRM_DEBUG_KMS("Invalid crtc for plane\n");
		ret = -EINVAL;
		goto out;
	}

2.3 检查plane是否支持该fb的pix format

	/* Check whether this plane supports the fb pixel format. */
	ret = drm_plane_check_pixel_format(plane, fb->format->format);
	if (ret) {
		struct drm_format_name_buf format_name;
		DRM_DEBUG_KMS("Invalid pixel format %s\n",
		              drm_get_format_name(fb->format->format,
		                                  &format_name));
		goto out;
	}

2.4 一些越界检查

	/* Give drivers some help against integer overflows */
	if (crtc_w > INT_MAX ||
	    crtc_x > INT_MAX - (int32_t) crtc_w ||
	    crtc_h > INT_MAX ||
	    crtc_y > INT_MAX - (int32_t) crtc_h) {
		DRM_DEBUG_KMS("Invalid CRTC coordinates %ux%u+%d+%d\n",
			      crtc_w, crtc_h, crtc_x, crtc_y);
		ret = -ERANGE;
		goto out;
	}

2.5 检查对齐情况

	ret = drm_framebuffer_check_src_coords(src_x, src_y, src_w, src_h, fb);
	if (ret)
		goto out;

2.6 调用plane->funcs->update_plane（drm_atomic_helper_update_plane）

	plane->old_fb = plane->fb;
	ret = plane->funcs->update_plane(plane, crtc, fb,
					 crtc_x, crtc_y, crtc_w, crtc_h,
					 src_x, src_y, src_w, src_h, ctx);
	if (!ret) {
		plane->crtc = crtc;
		plane->fb = fb;
		fb = NULL;
	} else {
		plane->old_fb = NULL;
	}

static const struct drm_plane_funcs malidp_de_plane_funcs = {
	.update_plane = drm_atomic_helper_update_plane,
	.disable_plane = drm_atomic_helper_disable_plane,
	.destroy = malidp_de_plane_destroy,
	.reset = malidp_plane_reset,
	.atomic_duplicate_state = malidp_duplicate_plane_state,
	.atomic_destroy_state = malidp_destroy_plane_state,
	.atomic_print_state = malidp_plane_atomic_print_state,
};

3. drm_atomic_helper_update_plane

int drm_atomic_helper_update_plane(struct drm_plane *plane,
				   struct drm_crtc *crtc,
				   struct drm_framebuffer *fb,
				   int crtc_x, int crtc_y,
				   unsigned int crtc_w, unsigned int crtc_h,
				   uint32_t src_x, uint32_t src_y,
				   uint32_t src_w, uint32_t src_h,
				   struct drm_modeset_acquire_ctx *ctx)
{
	struct drm_atomic_state *state;
	struct drm_plane_state *plane_state;
	int ret = 0;

	state = drm_atomic_state_alloc(plane->dev);
	if (!state)
		return -ENOMEM;

	state->acquire_ctx = ctx;
	plane_state = drm_atomic_get_plane_state(state, plane);
	if (IS_ERR(plane_state)) {
		ret = PTR_ERR(plane_state);
		goto fail;
	}

	ret = drm_atomic_set_crtc_for_plane(plane_state, crtc);
	if (ret != 0)
		goto fail;
	drm_atomic_set_fb_for_plane(plane_state, fb);
	plane_state->crtc_x = crtc_x;
	plane_state->crtc_y = crtc_y;
	plane_state->crtc_w = crtc_w;
	plane_state->crtc_h = crtc_h;
	plane_state->src_x = src_x;
	plane_state->src_y = src_y;
	plane_state->src_w = src_w;
	plane_state->src_h = src_h;

	if (plane == crtc->cursor)
		state->legacy_cursor_update = true;

	ret = drm_atomic_commit(state);
fail:
	drm_atomic_state_put(state);
	return ret;
}

        drm_atomic_helper_update_plane最终也会调用drm_atomic_commit，而且其参数都是struct drm_atomic_state。后面我们单独分析。

3.1 drm_atomic_set_fb_for_plane 把framebuffer引用给plane

void
drm_atomic_set_fb_for_plane(struct drm_plane_state *plane_state,
			    struct drm_framebuffer *fb)
{
	if (fb)
		DRM_DEBUG_ATOMIC("Set [FB:%d] for plane state %p\n",
				 fb->base.id, plane_state);
	else
		DRM_DEBUG_ATOMIC("Set [NOFB] for plane state %p\n",
				 plane_state);

	drm_framebuffer_assign(&plane_state->fb, fb);
}

4. 流程图