aux-bridge.c

  1// SPDX-License-Identifier: GPL-2.0+
  2/*
  3 * Copyright (C) 2023 Linaro Ltd.
  4 *
  5 * Author: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
  6 */
  7#include <linux/auxiliary_bus.h>
  8#include <linux/export.h>
  9#include <linux/module.h>
 10#include <linux/of.h>
 11
 12#include <drm/drm_bridge.h>
 13#include <drm/bridge/aux-bridge.h>
 14
 15static DEFINE_IDA(drm_aux_bridge_ida);
 16
 17static void drm_aux_bridge_release(struct device *dev)
 18{
 19	struct auxiliary_device *adev = to_auxiliary_dev(dev);
 20
 21	of_node_put(dev->of_node);
 22	ida_free(&drm_aux_bridge_ida, adev->id);
 23
 24	kfree(adev);
 25}
 26
 27static void drm_aux_bridge_unregister_adev(void *_adev)
 28{
 29	struct auxiliary_device *adev = _adev;
 30
 31	auxiliary_device_delete(adev);
 32	auxiliary_device_uninit(adev);
 33}
 34
 35/**
 36 * drm_aux_bridge_register - Create a simple bridge device to link the chain
 37 * @parent: device instance providing this bridge
 38 *
 39 * Creates a simple DRM bridge that doesn't implement any drm_bridge
 40 * operations. Such bridges merely fill a place in the bridge chain linking
 41 * surrounding DRM bridges.
 42 *
 43 * Return: zero on success, negative error code on failure
 44 */
 45int drm_aux_bridge_register(struct device *parent)
 46{
 47	struct auxiliary_device *adev;
 48	int ret;
 49
 50	adev = kzalloc(sizeof(*adev), GFP_KERNEL);
 51	if (!adev)
 52		return -ENOMEM;
 53
 54	ret = ida_alloc(&drm_aux_bridge_ida, GFP_KERNEL);
 55	if (ret < 0) {
 56		kfree(adev);
 57		return ret;
 58	}
 59
 60	adev->id = ret;
 61	adev->name = "aux_bridge";
 62	adev->dev.parent = parent;
 63	adev->dev.release = drm_aux_bridge_release;
 64
 65	device_set_of_node_from_dev(&adev->dev, parent);
 66
 67	ret = auxiliary_device_init(adev);
 68	if (ret) {
 69		of_node_put(adev->dev.of_node);
 70		ida_free(&drm_aux_bridge_ida, adev->id);
 71		kfree(adev);
 72		return ret;
 73	}
 74
 75	ret = auxiliary_device_add(adev);
 76	if (ret) {
 77		auxiliary_device_uninit(adev);
 78		return ret;
 79	}
 80
 81	return devm_add_action_or_reset(parent, drm_aux_bridge_unregister_adev, adev);
 82}
 83EXPORT_SYMBOL_GPL(drm_aux_bridge_register);
 84
 85struct drm_aux_bridge_data {
 86	struct drm_bridge bridge;
 87	struct drm_bridge *next_bridge;
 88	struct device *dev;
 89};
 90
 91static int drm_aux_bridge_attach(struct drm_bridge *bridge,
 92				 struct drm_encoder *encoder,
 93				 enum drm_bridge_attach_flags flags)
 94{
 95	struct drm_aux_bridge_data *data;
 96
 97	if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR))
 98		return -EINVAL;
 99
100	data = container_of(bridge, struct drm_aux_bridge_data, bridge);
101
102	return drm_bridge_attach(encoder, data->next_bridge, bridge,
103				 DRM_BRIDGE_ATTACH_NO_CONNECTOR);
104}
105
106static const struct drm_bridge_funcs drm_aux_bridge_funcs = {
107	.attach	= drm_aux_bridge_attach,
108};
109
110static int drm_aux_bridge_probe(struct auxiliary_device *auxdev,
111				const struct auxiliary_device_id *id)
112{
113	struct drm_aux_bridge_data *data;
114
115	data = devm_drm_bridge_alloc(&auxdev->dev, struct drm_aux_bridge_data,
116				     bridge, &drm_aux_bridge_funcs);
117	if (IS_ERR(data))
118		return PTR_ERR(data);
119
120	data->dev = &auxdev->dev;
121	data->next_bridge = devm_drm_of_get_bridge(&auxdev->dev, auxdev->dev.of_node, 0, 0);
122	if (IS_ERR(data->next_bridge))
123		return dev_err_probe(&auxdev->dev, PTR_ERR(data->next_bridge),
124				     "failed to acquire drm_bridge\n");
125
126	data->bridge.of_node = data->dev->of_node;
127
128	/* passthrough data, allow everything */
129	data->bridge.interlace_allowed = true;
130	data->bridge.ycbcr_420_allowed = true;
131
132	return devm_drm_bridge_add(data->dev, &data->bridge);
133}
134
135static const struct auxiliary_device_id drm_aux_bridge_table[] = {
136	{ .name = KBUILD_MODNAME ".aux_bridge" },
137	{},
138};
139MODULE_DEVICE_TABLE(auxiliary, drm_aux_bridge_table);
140
141static struct auxiliary_driver drm_aux_bridge_drv = {
142	.name = "aux_bridge",
143	.id_table = drm_aux_bridge_table,
144	.probe = drm_aux_bridge_probe,
145};
146module_auxiliary_driver(drm_aux_bridge_drv);
147
148MODULE_AUTHOR("Dmitry Baryshkov <dmitry.baryshkov@linaro.org>");
149MODULE_DESCRIPTION("DRM transparent bridge");
150MODULE_LICENSE("GPL");