Linux内核4.14版本——drm框架分析(9)——DRM_IOCTL_MODE_GETCONNECTOR（drm_mode_getconnector）

目录

 1. drm_mode_getconnector分析

1.1 找到connector

1.2 计算该connector的encoder数量

1.3 把connector支持的encoder和数量返回给用户

1.4 把找到的connector的参数返回给应用

1.5 填充mode（很重要）

1.6 把找到的connector的参数返回给应用

1.7 计算mode的数量

1.8 把mode的参数和mode的数量返回给应用

1.9 得到该connector的best encoder

1.10 刷新参数

2. fill_mode --> drm_helper_probe_single_connector_modes

2.1 所有的mode标记为旧的

2.2 热插拔相关

2.3 加载modes

2.3.1 加载固件edid的mode

2.3.2 如果没有读到2.3.1描述的edid，那么加载drm框架自带的mode

2.3.3 把命令行指定的modes加入到connector->probed_modes链表中

2.4 把modes从probed_modes链表移到modes链表

2.5 一些flags的设置

2.6 一些mode的检查的valid检查

2.6.1 drm_mode_validate_pipeline

2.7 调用drm_mode_prune_invalid把mode状态不是OK的移除链表

3. 流程图调用

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        本文分析一下APP调用ioctl传入DRM_IOCTL_MODE_GETCONNECTOR的操作，其对应kernel为drm_mode_getconnector函数。

 1. drm_mode_getconnector分析

1.1 找到connector

int drm_mode_getconnector(struct drm_device *dev, void *data,
			  struct drm_file *file_priv)
{
	struct drm_mode_get_connector *out_resp = data;
	struct drm_connector *connector;
	struct drm_encoder *encoder;
	struct drm_display_mode *mode;
	int mode_count = 0;
	int encoders_count = 0;
	int ret = 0;
	int copied = 0;
	int i;
	struct drm_mode_modeinfo u_mode;
	struct drm_mode_modeinfo __user *mode_ptr;
	uint32_t __user *encoder_ptr;

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

	memset(&u_mode, 0, sizeof(struct drm_mode_modeinfo));

	connector = drm_connector_lookup(dev, out_resp->connector_id);            // (1)
	if (!connector)
		return -ENOENT;

1.2 计算该connector的encoder数量

	for (i = 0; i < DRM_CONNECTOR_MAX_ENCODER; i++)                           // (2)
		if (connector->encoder_ids[i] != 0)
			encoders_count++;

1.3 把connector支持的encoder和数量返回给用户

	if ((out_resp->count_encoders >= encoders_count) && encoders_count) {     // (3)
		copied = 0;
		encoder_ptr = (uint32_t __user *)(unsigned long)(out_resp->encoders_ptr);
		for (i = 0; i < DRM_CONNECTOR_MAX_ENCODER; i++) {
			if (connector->encoder_ids[i] != 0) {
				if (put_user(connector->encoder_ids[i],
					     encoder_ptr + copied)) {
					ret = -EFAULT;
					goto out;
				}
				copied++;
			}
		}
	}
	out_resp->count_encoders = encoders_count;  

1.4 把找到的connector的参数返回给应用

	out_resp->connector_id = connector->base.id;							// (4)
	out_resp->connector_type = connector->connector_type;
	out_resp->connector_type_id = connector->connector_type_id;

1.5 填充mode（很重要）

	mutex_lock(&dev->mode_config.mutex); 
	if (out_resp->count_modes == 0) {                                      // (5)
		connector->funcs->fill_modes(connector,
					     dev->mode_config.max_width,
					     dev->mode_config.max_height);
	}

1.6 把找到的connector的参数返回给应用

	out_resp->mm_width = connector->display_info.width_mm;                 // (6)
	out_resp->mm_height = connector->display_info.height_mm;
	out_resp->subpixel = connector->display_info.subpixel_order;
	out_resp->connection = connector->status;

1.7 计算mode的数量

	/* delayed so we get modes regardless of pre-fill_modes state */
	list_for_each_entry(mode, &connector->modes, head)                     // (7)
		if (drm_mode_expose_to_userspace(mode, file_priv))
			mode_count++;

1.8 把mode的参数和mode的数量返回给应用

	/*
	 * This ioctl is called twice, once to determine how much space is
	 * needed, and the 2nd time to fill it.
	 */
	if ((out_resp->count_modes >= mode_count) && mode_count) {              // (8)
		copied = 0;
		mode_ptr = (struct drm_mode_modeinfo __user *)(unsigned long)out_resp->modes_ptr;
		list_for_each_entry(mode, &connector->modes, head) {
			if (!drm_mode_expose_to_userspace(mode, file_priv))
				continue;

			drm_mode_convert_to_umode(&u_mode, mode);
			if (copy_to_user(mode_ptr + copied,
					 &u_mode, sizeof(u_mode))) {
				ret = -EFAULT;
				mutex_unlock(&dev->mode_config.mutex);

				goto out;
			}
			copied++;
		}
	}
	out_resp->count_modes = mode_count;

1.9 得到该connector的best encoder

	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
	encoder = drm_connector_get_encoder(connector);                        // (9)
	if (encoder)
		out_resp->encoder_id = encoder->base.id;
	else
		out_resp->encoder_id = 0;

1.10 刷新参数

	/* Only grab properties after probing, to make sure EDID and other
	 * properties reflect the latest status. */                             // (10)
	ret = drm_mode_object_get_properties(&connector->base, file_priv->atomic,
			(uint32_t __user *)(unsigned long)(out_resp->props_ptr),
			(uint64_t __user *)(unsigned long)(out_resp->prop_values_ptr),
			&out_resp->count_props);
	drm_modeset_unlock(&dev->mode_config.connection_mutex);

2. fill_mode --> drm_helper_probe_single_connector_modes

static const struct drm_connector_funcs dw_hdmi_connector_funcs = {
	.fill_modes = drm_helper_probe_single_connector_modes,
	.detect = dw_hdmi_connector_detect,
	.destroy = drm_connector_cleanup,
	.force = dw_hdmi_connector_force,
	.reset = drm_atomic_helper_connector_reset,
	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
};

static const struct drm_connector_helper_funcs dw_hdmi_connector_helper_funcs = {
	.get_modes = dw_hdmi_connector_get_modes,
	.best_encoder = drm_atomic_helper_best_encoder,
};

        下面我们来分析一下这个函数。

2.1 所有的mode标记为旧的

int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
					    uint32_t maxX, uint32_t maxY)
{
    .......
	/* set all old modes to the stale state */
	list_for_each_entry(mode, &connector->modes, head)
		mode->status = MODE_STALE;

2.2 热插拔相关

	old_status = connector->status;

	if (connector->force) {
		if (connector->force == DRM_FORCE_ON ||
		    connector->force == DRM_FORCE_ON_DIGITAL)
			connector->status = connector_status_connected;
		else
			connector->status = connector_status_disconnected;
		if (connector->funcs->force)
			connector->funcs->force(connector);
	} else {
		ret = drm_helper_probe_detect(connector, &ctx, true);

		if (ret == -EDEADLK) {
			drm_modeset_backoff(&ctx);
			goto retry;
		} else if (WARN(ret < 0, "Invalid return value %i for connector detection\n", ret))
			ret = connector_status_unknown;

		connector->status = ret;
	}

	/*
	 * Normally either the driver's hpd code or the poll loop should
	 * pick up any changes and fire the hotplug event. But if
	 * userspace sneaks in a probe, we might miss a change. Hence
	 * check here, and if anything changed start the hotplug code.
	 */
	if (old_status != connector->status) {
		DRM_DEBUG_KMS("[CONNECTOR:%d:%s] status updated from %s to %s\n",
			      connector->base.id,
			      connector->name,
			      drm_get_connector_status_name(old_status),
			      drm_get_connector_status_name(connector->status));

		/*
		 * The hotplug event code might call into the fb
		 * helpers, and so expects that we do not hold any
		 * locks. Fire up the poll struct instead, it will
		 * disable itself again.
		 */
		dev->mode_config.delayed_event = true;
		if (dev->mode_config.poll_enabled)
			schedule_delayed_work(&dev->mode_config.output_poll_work,
					      0);
	}

	/* Re-enable polling in case the global poll config changed. */
	if (drm_kms_helper_poll != dev->mode_config.poll_running)
		drm_kms_helper_poll_enable(dev);

	dev->mode_config.poll_running = drm_kms_helper_poll;

       热插拔相关，这里不详细介绍

2.3 加载modes

2.3.1 加载固件edid的mode

	if (connector->override_edid) {
		struct edid *edid = (struct edid *) connector->edid_blob_ptr->data;

		count = drm_add_edid_modes(connector, edid);
		drm_edid_to_eld(connector, edid);
	} else {
		struct edid *edid = drm_load_edid_firmware(connector);
		if (!IS_ERR_OR_NULL(edid)) {
			drm_mode_connector_update_edid_property(connector, edid);
			count = drm_add_edid_modes(connector, edid);
			drm_edid_to_eld(connector, edid);
			kfree(edid);
		}
		if (count == 0)
			count = (*connector_funcs->get_modes)(connector);
	}

        connector->override_edid是测试相关的，正式开发中不会用到，这里不讨论。这里做了两件事，如下：

       （1）直接加载edid固件文件，一般存储在固定的位置，会在环境变量中指定。后使用drm_add_edid_modes添加modes。

       （2）如果没有指定edid固件文件，那么就从connector helper的get_modes中获取，这里一般和显示器有关，hdmi会读取外接显示器的edid，本文使用的是dw-hdmi，get_modes调用的是dw_hdmi_connector_get_modes。

static const struct drm_connector_funcs dw_hdmi_connector_funcs = {
	.fill_modes = drm_helper_probe_single_connector_modes,
	.detect = dw_hdmi_connector_detect,
	.destroy = drm_connector_cleanup,
	.force = dw_hdmi_connector_force,
	.reset = drm_atomic_helper_connector_reset,
	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
};

static const struct drm_connector_helper_funcs dw_hdmi_connector_helper_funcs = {
	.get_modes = dw_hdmi_connector_get_modes,
	.best_encoder = drm_atomic_helper_best_encoder,
};

static int dw_hdmi_connector_get_modes(struct drm_connector *connector)
{
	struct dw_hdmi *hdmi = container_of(connector, struct dw_hdmi,
					     connector);
	struct edid *edid;
	int ret = 0;

	if (!hdmi->ddc)
		return 0;

	edid = drm_get_edid(connector, hdmi->ddc);
	if (edid) {
		dev_dbg(hdmi->dev, "got edid: width[%d] x height[%d]\n",
			edid->width_cm, edid->height_cm);

		hdmi->sink_is_hdmi = drm_detect_hdmi_monitor(edid);
		hdmi->sink_has_audio = drm_detect_monitor_audio(edid);
		drm_mode_connector_update_edid_property(connector, edid);
		cec_notifier_set_phys_addr_from_edid(hdmi->cec_notifier, edid);
		ret = drm_add_edid_modes(connector, edid);
		/* Store the ELD */
		drm_edid_to_eld(connector, edid);
		kfree(edid);
	} else {
		dev_dbg(hdmi->dev, "failed to get edid\n");
	}

	return ret;
}

       也是读取edid的相关信息，这里不做介绍了。

2.3.2 如果没有读到2.3.1描述的edid，那么加载drm框架自带的mode

	if (count == 0 && connector->status == connector_status_connected)
		count = drm_add_modes_noedid(connector, 1024, 768);

2.3.3 把命令行指定的modes加入到connector->probed_modes链表中

	count += drm_helper_probe_add_cmdline_mode(connector);
	if (count == 0)
		goto prune;

2.4 把modes从probed_modes链表移到modes链表

/**
 * drm_mode_connector_list_update - update the mode list for the connector
 * @connector: the connector to update
 *
 * This moves the modes from the @connector probed_modes list
 * to the actual mode list. It compares the probed mode against the current
 * list and only adds different/new modes.
 *
 * This is just a helper functions doesn't validate any modes itself and also
 * doesn't prune any invalid modes. Callers need to do that themselves.
 */
void drm_mode_connector_list_update(struct drm_connector *connector)
{
	struct drm_display_mode *pmode, *pt;

	WARN_ON(!mutex_is_locked(&connector->dev->mode_config.mutex));

	list_for_each_entry_safe(pmode, pt, &connector->probed_modes, head) {
		struct drm_display_mode *mode;
		bool found_it = false;

		/* go through current modes checking for the new probed mode */
		list_for_each_entry(mode, &connector->modes, head) {
			if (!drm_mode_equal(pmode, mode))
				continue;

			found_it = true;

			/*
			 * If the old matching mode is stale (ie. left over
			 * from a previous probe) just replace it outright.
			 * Otherwise just merge the type bits between all
			 * equal probed modes.
			 *
			 * If two probed modes are considered equal, pick the
			 * actual timings from the one that's marked as
			 * preferred (in case the match isn't 100%). If
			 * multiple or zero preferred modes are present, favor
			 * the mode added to the probed_modes list first.
			 */
			if (mode->status == MODE_STALE) {
				drm_mode_copy(mode, pmode);
			} else if ((mode->type & DRM_MODE_TYPE_PREFERRED) == 0 &&
				   (pmode->type & DRM_MODE_TYPE_PREFERRED) != 0) {
				pmode->type |= mode->type;
				drm_mode_copy(mode, pmode);
			} else {
				mode->type |= pmode->type;
			}

			list_del(&pmode->head);
			drm_mode_destroy(connector->dev, pmode);
			break;
		}

		if (!found_it) {
			list_move_tail(&pmode->head, &connector->modes);
		}
	}
}

       主要是把重复的probe_modes链表和modes链表中重复的mode删除，此函数运行以后，probe_modes链表就为空了，为下次做准备。

2.5 一些flags的设置

	if (connector->interlace_allowed)
		mode_flags |= DRM_MODE_FLAG_INTERLACE;
	if (connector->doublescan_allowed)
		mode_flags |= DRM_MODE_FLAG_DBLSCAN;
	if (connector->stereo_allowed)
		mode_flags |= DRM_MODE_FLAG_3D_MASK;

2.6 一些mode的检查的valid检查

	list_for_each_entry(mode, &connector->modes, head) {
		if (mode->status == MODE_OK)
			mode->status = drm_mode_validate_basic(mode);

		if (mode->status == MODE_OK)
			mode->status = drm_mode_validate_size(mode, maxX, maxY);

		if (mode->status == MODE_OK)
			mode->status = drm_mode_validate_flag(mode, mode_flags);

		if (mode->status == MODE_OK)
			mode->status = drm_mode_validate_pipeline(mode,
								  connector);

		if (mode->status == MODE_OK)
			mode->status = drm_mode_validate_ycbcr420(mode,
								  connector);
	}

        （1）drm_mode_validate_basic做一些简单的检查

        （2）drm_mode_validate_size做一些越界的检查。

        （3）drm_mode_validate_flag做一些flag的检查（interlace_allowed,doublescan_allowed,stereo_allowed）

        （4）drm_mode_validate_pipeline调用connector、encoder、crtc的helper func mode_valid做一些检查。

        （5）drm_mode_validate_ycbcr420检查是否支持YUV420。

2.6.1 drm_mode_validate_pipeline

static enum drm_mode_status
drm_mode_validate_pipeline(struct drm_display_mode *mode,
			    struct drm_connector *connector)
{
	struct drm_device *dev = connector->dev;
	uint32_t *ids = connector->encoder_ids;
	enum drm_mode_status ret = MODE_OK;
	unsigned int i;

	/* Step 1: Validate against connector */
	ret = drm_connector_mode_valid(connector, mode);
	if (ret != MODE_OK)
		return ret;

	/* Step 2: Validate against encoders and crtcs */
	for (i = 0; i < DRM_CONNECTOR_MAX_ENCODER; i++) {
		struct drm_encoder *encoder = drm_encoder_find(dev, ids[i]);
		struct drm_crtc *crtc;

		if (!encoder)
			continue;

		ret = drm_encoder_mode_valid(encoder, mode);

		ret = drm_bridge_mode_valid(encoder->bridge, mode);

		drm_for_each_crtc(crtc, dev) {
			if (!drm_encoder_crtc_ok(encoder, crtc))
				continue;

			ret = drm_crtc_mode_valid(crtc, mode);
		}
	}

	return ret;
}

        drm_connector_mode_valid ---> connector_funcs->mode_valid(connector, mode);

        drm_encoder_mode_valid ----> encoder_funcs->mode_valid(encoder, mode);

        drm_bridge_mode_valid ----> bridge->funcs->mode_valid(bridge, mode);

        drm_crtc_mode_valid ---> crtc_funcs->mode_valid(crtc, mode);

2.7 调用drm_mode_prune_invalid把mode状态不是OK的移除链表

void drm_mode_prune_invalid(struct drm_device *dev,
			    struct list_head *mode_list, bool verbose)
{
	struct drm_display_mode *mode, *t;

	list_for_each_entry_safe(mode, t, mode_list, head) {
		if (mode->status != MODE_OK) {
			list_del(&mode->head);
			if (verbose) {
				drm_mode_debug_printmodeline(mode);
				DRM_DEBUG_KMS("Not using %s mode: %s\n",
					      mode->name,
					      drm_get_mode_status_name(mode->status));
			}
			drm_mode_destroy(dev, mode);
		}
	}
}

3. 流程图调用