目录

1. drm_mode_setcrtc

1.1 根据应用传入的crtc_id找到crtc

1.2 根据应用传入的fb_id,找到对应的drm_framebuffer

1.3  根据应用传入的mode，创建一个drm_display_mode

1.4 根据传入的set_connectors_ptr，找到驱动对应的connector

1.5 将以上信息转为struct drm_mode_set并调用__drm_mode_set_config_internal

1.6 __drm_mode_set_config_internal

2. drm_atomic_helper_set_config

3. 流程图

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        本文分析一下drm_mode_setcrtc。

1. drm_mode_setcrtc

1.1 根据应用传入的crtc_id找到crtc

int drm_mode_setcrtc(struct drm_device *dev, void *data,
		     struct drm_file *file_priv)
{
    ......

	crtc = drm_crtc_find(dev, crtc_req->crtc_id);
	if (!crtc) {
		DRM_DEBUG_KMS("Unknown CRTC ID %d\n", crtc_req->crtc_id);
		return -ENOENT;
	}
	DRM_DEBUG_KMS("[CRTC:%d:%s]\n", crtc->base.id, crtc->name);

1.2 根据应用传入的fb_id,找到对应的drm_framebuffer

	if (crtc_req->mode_valid) {
		/* If we have a mode we need a framebuffer. */
		/* If we pass -1, set the mode with the currently bound fb */
		if (crtc_req->fb_id == -1) {
			if (!crtc->primary->fb) {
				DRM_DEBUG_KMS("CRTC doesn't have current FB\n");
				ret = -EINVAL;
				goto out;
			}
			fb = crtc->primary->fb;
			/* Make refcounting symmetric with the lookup path. */
			drm_framebuffer_get(fb);
		} else {
			fb = drm_framebuffer_lookup(dev, crtc_req->fb_id);
			if (!fb) {
				DRM_DEBUG_KMS("Unknown FB ID%d\n",
						crtc_req->fb_id);
				ret = -ENOENT;
				goto out;
			}

1.3  根据应用传入的mode，创建一个drm_display_mode

		mode = drm_mode_create(dev);
		if (!mode) {
			ret = -ENOMEM;
			goto out;
		}

		ret = drm_mode_convert_umode(mode, &crtc_req->mode);
		if (ret) {
			DRM_DEBUG_KMS("Invalid mode\n");
			goto out;
		}

		/*
		 * Check whether the primary plane supports the fb pixel format.
		 * Drivers not implementing the universal planes API use a
		 * default formats list provided by the DRM core which doesn't
		 * match real hardware capabilities. Skip the check in that
		 * case.
		 */
		if (!crtc->primary->format_default) {
			ret = drm_plane_check_pixel_format(crtc->primary,
							   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;
			}
		}

		ret = drm_crtc_check_viewport(crtc, crtc_req->x, crtc_req->y,
					      mode, fb);
		if (ret)
			goto out;

1.4 根据传入的set_connectors_ptr，找到驱动对应的connector

		for (i = 0; i < crtc_req->count_connectors; i++) {
			connector_set[i] = NULL;
			set_connectors_ptr = (uint32_t __user *)(unsigned long)crtc_req->set_connectors_ptr;
			if (get_user(out_id, &set_connectors_ptr[i])) {
				ret = -EFAULT;
				goto out;
			}

			connector = drm_connector_lookup(dev, out_id);
			if (!connector) {
				DRM_DEBUG_KMS("Connector id %d unknown\n",
						out_id);
				ret = -ENOENT;
				goto out;
			}
			DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
					connector->base.id,
					connector->name);

			connector_set[i] = connector;
		}

1.5 将以上信息转为struct drm_mode_set并调用__drm_mode_set_config_internal

	set.crtc = crtc;
	set.x = crtc_req->x;
	set.y = crtc_req->y;
	set.mode = mode;
	set.connectors = connector_set;
	set.num_connectors = crtc_req->count_connectors;
	set.fb = fb;
	ret = __drm_mode_set_config_internal(&set, &ctx);

1.6 __drm_mode_set_config_internal

static int __drm_mode_set_config_internal(struct drm_mode_set *set,
					  struct drm_modeset_acquire_ctx *ctx)
{
	struct drm_crtc *crtc = set->crtc;
	struct drm_framebuffer *fb;
	struct drm_crtc *tmp;
	int ret;

	/*
	 * NOTE: ->set_config can also disable other crtcs (if we steal all
	 * connectors from it), hence we need to refcount the fbs across all
	 * crtcs. Atomic modeset will have saner semantics ...
	 */
	drm_for_each_crtc(tmp, crtc->dev)
		tmp->primary->old_fb = tmp->primary->fb;

	fb = set->fb;

	ret = crtc->funcs->set_config(set, ctx);
	if (ret == 0) {
		crtc->primary->crtc = crtc;
		crtc->primary->fb = fb;
	}

	drm_for_each_crtc(tmp, crtc->dev) {
		if (tmp->primary->fb)
			drm_framebuffer_get(tmp->primary->fb);
		if (tmp->primary->old_fb)
			drm_framebuffer_put(tmp->primary->old_fb);
		tmp->primary->old_fb = NULL;
	}

	return ret;
}

        只要是调用ret = crtc->funcs->set_config(set, ctx)，即drm_atomic_helper_set_config，

static const struct drm_crtc_funcs malidp_crtc_funcs = {
	.gamma_set = drm_atomic_helper_legacy_gamma_set,
	.destroy = drm_crtc_cleanup,
	.set_config = drm_atomic_helper_set_config,
	.page_flip = drm_atomic_helper_page_flip,
	.reset = malidp_crtc_reset,
	.atomic_duplicate_state = malidp_crtc_duplicate_state,
	.atomic_destroy_state = malidp_crtc_destroy_state,
	.enable_vblank = malidp_crtc_enable_vblank,
	.disable_vblank = malidp_crtc_disable_vblank,
};

2. drm_atomic_helper_set_config

int drm_atomic_helper_set_config(struct drm_mode_set *set,
				 struct drm_modeset_acquire_ctx *ctx)
{
	struct drm_atomic_state *state;
	struct drm_crtc *crtc = set->crtc;
	int ret = 0;

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

	state->acquire_ctx = ctx;
	ret = __drm_atomic_helper_set_config(set, state);
	if (ret != 0)
		goto fail;

	ret = handle_conflicting_encoders(state, true);
	if (ret)
		goto fail;

	ret = drm_atomic_commit(state);

fail:
	drm_atomic_state_put(state);
	return ret;
}

        drm_atomic_helper_set_config主要涉及到结构体struct drm_atomic_state和drm_atomic_commit函数，我们后面会单独讨论这2个。

3. 流程图