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(node: dev->of_node);
22 ida_free(&drm_aux_bridge_ida, id: adev->id);
23
24 kfree(objp: adev);
25}
26
27static void drm_aux_bridge_unregister_adev(void *_adev)
28{
29 struct auxiliary_device *adev = _adev;
30
31 auxiliary_device_delete(auxdev: adev);
32 auxiliary_device_uninit(auxdev: 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(ida: &drm_aux_bridge_ida, GFP_KERNEL);
55 if (ret < 0) {
56 kfree(objp: 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(dev: &adev->dev, dev2: parent);
66
67 ret = auxiliary_device_init(auxdev: adev);
68 if (ret) {
69 of_node_put(node: adev->dev.of_node);
70 ida_free(&drm_aux_bridge_ida, id: adev->id);
71 kfree(objp: adev);
72 return ret;
73 }
74
75 ret = auxiliary_device_add(adev);
76 if (ret) {
77 auxiliary_device_uninit(auxdev: 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, bridge: data->next_bridge, previous: bridge,
103 flags: 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(ptr: data))
118 return PTR_ERR(ptr: data);
119
120 data->dev = &auxdev->dev;
121 data->next_bridge = devm_drm_of_get_bridge(dev: &auxdev->dev, node: auxdev->dev.of_node, port: 0, endpoint: 0);
122 if (IS_ERR(ptr: data->next_bridge))
123 return dev_err_probe(dev: &auxdev->dev, err: PTR_ERR(ptr: data->next_bridge),
124 fmt: "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(dev: data->dev, bridge: &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");
151

source code of linux/drivers/gpu/drm/bridge/aux-bridge.c