1. 根目录:
2. drivers
3. gpu
4. drm
5. drm_of.c

#include <linux/component.h>
#include <linux/export.h>
#include <linux/list.h>
#include <linux/of_graph.h>
#include <drm/drmP.h>
#include <drm/drm_crtc.h>
#include <drm/drm_of.h>

/**
 * drm_crtc_port_mask - find the mask of a registered CRTC by port OF node
 * @dev: DRM device
 * @port: port OF node
 *
 * Given a port OF node, return the possible mask of the corresponding
 * CRTC within a device's list of CRTCs.  Returns zero if not found.
 */
static uint32_t drm_crtc_port_mask(struct drm_device *dev,
				   struct device_node *port)
{
	unsigned int index = 0;
	struct drm_crtc *tmp;

	drm_for_each_crtc(tmp, dev) {
		if (tmp->port == port)
			return 1 << index;

		index++;
	}

	return 0;
}

/**
 * drm_of_find_possible_crtcs - find the possible CRTCs for an encoder port
 * @dev: DRM device
 * @port: encoder port to scan for endpoints
 *
 * Scan all endpoints attached to a port, locate their attached CRTCs,
 * and generate the DRM mask of CRTCs which may be attached to this
 * encoder.
 *
 * See Documentation/devicetree/bindings/graph.txt for the bindings.
 */
uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
				    struct device_node *port)
{
	struct device_node *remote_port, *ep;
	uint32_t possible_crtcs = 0;

	for_each_endpoint_of_node(port, ep) {
		remote_port = of_graph_get_remote_port(ep);
		if (!remote_port) {
			of_node_put(ep);
			return 0;
		}

		possible_crtcs |= drm_crtc_port_mask(dev, remote_port);

		of_node_put(remote_port);
	}

	return possible_crtcs;
}
EXPORT_SYMBOL(drm_of_find_possible_crtcs);

/**
 * drm_of_component_probe - Generic probe function for a component based master
 * @dev: master device containing the OF node
 * @compare_of: compare function used for matching components
 * @master_ops: component master ops to be used
 *
 * Parse the platform device OF node and bind all the components associated
 * with the master. Interface ports are added before the encoders in order to
 * satisfy their .bind requirements
 * See Documentation/devicetree/bindings/graph.txt for the bindings.
 *
 * Returns zero if successful, or one of the standard error codes if it fails.
 */
int drm_of_component_probe(struct device *dev,
			   int (*compare_of)(struct device *, void *),
			   const struct component_master_ops *m_ops)
{
	struct device_node *ep, *port, *remote;
	struct component_match *match = NULL;
	int i;

	if (!dev->of_node)
		return -EINVAL;

	/*
	 * Bind the crtc's ports first, so that drm_of_find_possible_crtcs()
	 * called from encoder's .bind callbacks works as expected
	 */
	for (i = 0; ; i++) {
		port = of_parse_phandle(dev->of_node, "ports", i);
		if (!port)
			break;

		if (!of_device_is_available(port->parent)) {
			of_node_put(port);
			continue;
		}

		component_match_add(dev, &match, compare_of, port);
		of_node_put(port);
	}

	if (i == 0) {
		dev_err(dev, "missing 'ports' property\n");
		return -ENODEV;
	}

	if (!match) {
		dev_err(dev, "no available port\n");
		return -ENODEV;
	}

	/*
	 * For bound crtcs, bind the encoders attached to their remote endpoint
	 */
	for (i = 0; ; i++) {
		port = of_parse_phandle(dev->of_node, "ports", i);
		if (!port)
			break;

		if (!of_device_is_available(port->parent)) {
			of_node_put(port);
			continue;
		}

		for_each_child_of_node(port, ep) {
			remote = of_graph_get_remote_port_parent(ep);
			if (!remote || !of_device_is_available(remote)) {
				of_node_put(remote);
				continue;
			} else if (!of_device_is_available(remote->parent)) {
				dev_warn(dev, "parent device of %s is not available\n",
					 remote->full_name);
				of_node_put(remote);
				continue;
			}

			component_match_add(dev, &match, compare_of, remote);
			of_node_put(remote);
		}
		of_node_put(port);
	}

	return component_master_add_with_match(dev, m_ops, match);
}
EXPORT_SYMBOL(drm_of_component_probe);