drivers/gpu/drm/bridge/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/module.h>
   9 #include <linux/of.h>
  10
  11 #include <drm/drm_bridge.h>
  12 #include <drm/bridge/aux-bridge.h>
  13
  14 static DEFINE_IDA(drm_aux_bridge_ida);
  15
  16 static 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
  25 static 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  */
  43 int 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 }
  79 EXPORT_SYMBOL_GPL(drm_aux_bridge_register);
  80
  81 struct drm_aux_bridge_data {
  82         struct drm_bridge bridge;
  83         struct drm_bridge *next_bridge;
  84         struct device *dev;
  85 };
  86
  87 static 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
 101 static const struct drm_bridge_funcs drm_aux_bridge_funcs = {
 102         .attach = drm_aux_bridge_attach,
 103 };
 104
 105 static 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
 126 static const struct auxiliary_device_id drm_aux_bridge_table[] = {
 127         { .name = KBUILD_MODNAME ".aux_bridge" },
 128         {},
 129 };
 130 MODULE_DEVICE_TABLE(auxiliary, drm_aux_bridge_table);
 131
 132 static 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 };
 137 module_auxiliary_driver(drm_aux_bridge_drv);
 138
 139 MODULE_AUTHOR("Dmitry Baryshkov <dmitry.baryshkov@linaro.org>");
 140 MODULE_DESCRIPTION("DRM transparent bridge");
 141 MODULE_LICENSE("GPL");