On Sat, 29 Jul 2023 at 23:43, Dmitry Baryshkov
<dmitry.baryshkov@xxxxxxxxxx> wrote:
>
> Define a helper for creating simple transparent bridges which serve the
> only purpose of linking devices into the bridge chain up to the last
> bridge representing the connector. This is especially useful for
> DP/USB-C bridge chains, which can span across several devices, but do
> not require any additional functionality from the intermediate bridges.
>
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> ---
> drivers/gpu/drm/display/Kconfig | 9 ++
> drivers/gpu/drm/display/Makefile | 2 +
> drivers/gpu/drm/display/drm_simple_bridge.c | 120 ++++++++++++++++++++
> include/drm/display/drm_simple_bridge.h | 19 ++++
> 4 files changed, 150 insertions(+)
> create mode 100644 drivers/gpu/drm/display/drm_simple_bridge.c
> create mode 100644 include/drm/display/drm_simple_bridge.h
>
> diff --git a/drivers/gpu/drm/display/Kconfig b/drivers/gpu/drm/display/Kconfig
> index 09712b88a5b8..a6132984b9e3 100644
> --- a/drivers/gpu/drm/display/Kconfig
> +++ b/drivers/gpu/drm/display/Kconfig
> @@ -49,3 +49,12 @@ config DRM_DP_CEC
>
> Note: not all adapters support this feature, and even for those
> that do support this they often do not hook up the CEC pin.
> +
> +config DRM_SIMPLE_BRIDGE
> + tristate
> + depends on DRM
> + select AUXILIARY_BUS
> + select DRM_PANEL_BRIDGE
> + help
> + Simple transparent bridge that is used by several drivers to build
> + bridges chain.
> diff --git a/drivers/gpu/drm/display/Makefile b/drivers/gpu/drm/display/Makefile
> index 17ac4a1006a8..6e2b0d7f24b3 100644
> --- a/drivers/gpu/drm/display/Makefile
> +++ b/drivers/gpu/drm/display/Makefile
> @@ -16,3 +16,5 @@ drm_display_helper-$(CONFIG_DRM_DP_AUX_CHARDEV) += drm_dp_aux_dev.o
> drm_display_helper-$(CONFIG_DRM_DP_CEC) += drm_dp_cec.o
>
> obj-$(CONFIG_DRM_DISPLAY_HELPER) += drm_display_helper.o
> +
> +obj-$(CONFIG_DRM_SIMPLE_BRIDGE) += drm_simple_bridge.o
> diff --git a/drivers/gpu/drm/display/drm_simple_bridge.c b/drivers/gpu/drm/display/drm_simple_bridge.c
> new file mode 100644
> index 000000000000..c9966691efb1
> --- /dev/null
> +++ b/drivers/gpu/drm/display/drm_simple_bridge.c
> @@ -0,0 +1,120 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright (C) 2023 Linaro Ltd.
> + *
> + * Author: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> + */
> +#include <linux/auxiliary_bus.h>
> +#include <linux/module.h>
> +
> +#include <drm/drm_bridge.h>
> +#include <drm/display/drm_simple_bridge.h>
> +
> +static DEFINE_IDA(simple_bridge_ida);
> +
> +static void drm_simple_bridge_release(struct device *dev)
> +{
> + struct auxiliary_device *adev = to_auxiliary_dev(dev);
> +
> + kfree(adev);
> +}
> +
> +static void drm_simple_bridge_unregister_adev(void *_adev)
> +{
> + struct auxiliary_device *adev = _adev;
> +
> + auxiliary_device_delete(adev);
> + auxiliary_device_uninit(adev);
> +}
> +
> +int drm_simple_bridge_register(struct device *parent)
> +{
> + struct auxiliary_device *adev;
> + int ret;
> +
> + adev = kzalloc(sizeof(*adev), GFP_KERNEL);
> + if (!adev)
> + return -ENOMEM;
> +
> + ret = ida_alloc(&simple_bridge_ida, GFP_KERNEL);
> + if (ret < 0)
> + return ret;
> +
> + adev->id = ret;
> + adev->name = "simple_bridge";
> + adev->dev.parent = parent;
> + adev->dev.of_node = parent->of_node;
> + adev->dev.release = drm_simple_bridge_release;
> +
> + ret = auxiliary_device_init(adev);
> + if (ret) {
> + kfree(adev);
> + return ret;
> + }
> +
> + ret = auxiliary_device_add(adev);
> + if (ret) {
> + auxiliary_device_uninit(adev);
> + return ret;
> + }
> +
> + return devm_add_action_or_reset(parent, drm_simple_bridge_unregister_adev, adev);
> +}
Forgot EXPORT_SYMBOL_GPL, MODULE_LICENSE, etc. I'll fix that for v2 if
the overall idea is found to be acceptable.
> +
> +struct drm_simple_bridge_data {
> + struct drm_bridge bridge;
> + struct drm_bridge *next_bridge;
> + struct device *dev;
> +};
> +
> +static int drm_simple_bridge_attach(struct drm_bridge *bridge,
> + enum drm_bridge_attach_flags flags)
> +{
> + struct drm_simple_bridge_data *data;
> +
> + if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR))
> + return -EINVAL;
> +
> + data = container_of(bridge, struct drm_simple_bridge_data, bridge);
> +
> + return drm_bridge_attach(bridge->encoder, data->next_bridge, bridge,
> + DRM_BRIDGE_ATTACH_NO_CONNECTOR);
> +}
> +
> +static const struct drm_bridge_funcs drm_simple_bridge_funcs = {
> + .attach = drm_simple_bridge_attach,
> +};
> +
> +static int drm_simple_bridge_probe(struct auxiliary_device *auxdev,
> + const struct auxiliary_device_id *id)
> +{
> + struct drm_simple_bridge_data *data;
> +
> + data = devm_kzalloc(&auxdev->dev, sizeof(*data), GFP_KERNEL);
> + if (!data)
> + return -ENOMEM;
> +
> + data->dev = &auxdev->dev;
> + data->next_bridge = devm_drm_of_get_bridge(&auxdev->dev, auxdev->dev.of_node, 0, 0);
> + if (IS_ERR(data->next_bridge))
> + return dev_err_probe(&auxdev->dev, PTR_ERR(data->next_bridge),
> + "failed to acquire drm_bridge\n");
> +
> + data->bridge.funcs = &drm_simple_bridge_funcs;
> + data->bridge.of_node = data->dev->of_node;
> +
> + return devm_drm_bridge_add(data->dev, &data->bridge);
> +}
> +
> +static const struct auxiliary_device_id drm_simple_bridge_table[] = {
> + { .name = KBUILD_MODNAME ".simple_bridge" },
> + {},
> +};
> +MODULE_DEVICE_TABLE(auxiliary, drm_simple_bridge_table);
> +
> +struct auxiliary_driver drm_simple_bridge_drv = {
> + .name = "simple_bridge",
> + .id_table = drm_simple_bridge_table,
> + .probe = drm_simple_bridge_probe,
> +};
> +module_auxiliary_driver(drm_simple_bridge_drv);
> diff --git a/include/drm/display/drm_simple_bridge.h b/include/drm/display/drm_simple_bridge.h
> new file mode 100644
> index 000000000000..3da8e1fb1137
> --- /dev/null
> +++ b/include/drm/display/drm_simple_bridge.h
> @@ -0,0 +1,19 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright (C) 2023 Linaro Ltd.
> + *
> + * Author: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> + */
> +#ifndef DRM_SIMPLE_BRIDGE_H
> +#define DRM_SIMPLE_BRIDGE_H
> +
> +#if IS_ENABLED(CONFIG_DRM_SIMPLE_BRIDGE)
> +int drm_simple_bridge_register(struct device *parent);
> +#else
> +static inline int drm_simple_bridge_register(struct device *parent)
> +{
> + return 0;
> +}
> +#endif
> +
> +#endif
> --
> 2.39.2
>
--
With best wishes
Dmitry
