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