Re: [PATCH v3 2/7] drm/bridge: Repurpose lvds-encoder.c

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Hi Fabrizio,

Thank you for the patch.

On Thu, Nov 07, 2019 at 08:10:58PM +0000, Fabrizio Castro wrote:
> lvds-encoder.c implementation is also suitable for LVDS decoders,
> not just LVDS encoders.
> Instead of creating a new driver for addressing support for
> transparent LVDS decoders, repurpose lvds-encoder.c for the greater
> good.
> 
> Signed-off-by: Fabrizio Castro <fabrizio.castro@xxxxxxxxxxxxxx>
> 
> ---
> v2->v3:
> * No change
> v1->v2:
> * No change
> ---
>  drivers/gpu/drm/bridge/Kconfig        |   8 +-
>  drivers/gpu/drm/bridge/Makefile       |   2 +-
>  drivers/gpu/drm/bridge/lvds-codec.c   | 131 ++++++++++++++++++++++++++++
>  drivers/gpu/drm/bridge/lvds-encoder.c | 155 ----------------------------------
>  4 files changed, 136 insertions(+), 160 deletions(-)

It would help if you added the -M1 option to git-format-patch to detect
the rename, the result would be easier to review.

>  create mode 100644 drivers/gpu/drm/bridge/lvds-codec.c
>  delete mode 100644 drivers/gpu/drm/bridge/lvds-encoder.c
> 
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index 3436297..9e75ca4e 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -45,14 +45,14 @@ config DRM_DUMB_VGA_DAC
>  	  Support for non-programmable RGB to VGA DAC bridges, such as ADI
>  	  ADV7123, TI THS8134 and THS8135 or passive resistor ladder DACs.
>  
> -config DRM_LVDS_ENCODER
> -	tristate "Transparent parallel to LVDS encoder support"
> +config DRM_LVDS_CODEC
> +	tristate "Transparent LVDS encoders and decoders support"
>  	depends on OF
>  	select DRM_KMS_HELPER
>  	select DRM_PANEL_BRIDGE
>  	help
> -	  Support for transparent parallel to LVDS encoders that don't require
> -	  any configuration.
> +	  Support for transparent LVDS encoders and LVDS decoders that don't
> +	  require any configuration.
>  
>  config DRM_MEGACHIPS_STDPXXXX_GE_B850V3_FW
>  	tristate "MegaChips stdp4028-ge-b850v3-fw and stdp2690-ge-b850v3-fw"
> diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
> index 4934fcf..8a9178a 100644
> --- a/drivers/gpu/drm/bridge/Makefile
> +++ b/drivers/gpu/drm/bridge/Makefile
> @@ -2,7 +2,7 @@
>  obj-$(CONFIG_DRM_ANALOGIX_ANX78XX) += analogix-anx78xx.o
>  obj-$(CONFIG_DRM_CDNS_DSI) += cdns-dsi.o
>  obj-$(CONFIG_DRM_DUMB_VGA_DAC) += dumb-vga-dac.o
> -obj-$(CONFIG_DRM_LVDS_ENCODER) += lvds-encoder.o
> +obj-$(CONFIG_DRM_LVDS_CODEC) += lvds-codec.o
>  obj-$(CONFIG_DRM_MEGACHIPS_STDPXXXX_GE_B850V3_FW) += megachips-stdpxxxx-ge-b850v3-fw.o
>  obj-$(CONFIG_DRM_NXP_PTN3460) += nxp-ptn3460.o
>  obj-$(CONFIG_DRM_PARADE_PS8622) += parade-ps8622.o
> diff --git a/drivers/gpu/drm/bridge/lvds-codec.c b/drivers/gpu/drm/bridge/lvds-codec.c
> new file mode 100644
> index 0000000..d57a8eb
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/lvds-codec.c
> @@ -0,0 +1,131 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (C) 2019 Renesas Electronics Corporation
> + * Copyright (C) 2016 Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> + */
> +
> +#include <linux/gpio/consumer.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/of_graph.h>
> +#include <linux/platform_device.h>
> +
> +#include <drm/drm_bridge.h>
> +#include <drm/drm_panel.h>
> +
> +struct lvds_codec {
> +	struct drm_bridge bridge;
> +	struct drm_bridge *panel_bridge;
> +	struct gpio_desc *powerdown_gpio;
> +};
> +
> +static int lvds_codec_attach(struct drm_bridge *bridge)
> +{
> +	struct lvds_codec *lvds_codec = container_of(bridge,
> +						     struct lvds_codec, bridge);
> +
> +	return drm_bridge_attach(bridge->encoder, lvds_codec->panel_bridge,
> +				 bridge);
> +}
> +
> +static void lvds_codec_enable(struct drm_bridge *bridge)
> +{
> +	struct lvds_codec *lvds_codec = container_of(bridge,
> +						     struct lvds_codec, bridge);
> +
> +	if (lvds_codec->powerdown_gpio)
> +		gpiod_set_value_cansleep(lvds_codec->powerdown_gpio, 0);
> +}
> +
> +static void lvds_codec_disable(struct drm_bridge *bridge)
> +{
> +	struct lvds_codec *lvds_codec = container_of(bridge,
> +						     struct lvds_codec, bridge);
> +
> +	if (lvds_codec->powerdown_gpio)
> +		gpiod_set_value_cansleep(lvds_codec->powerdown_gpio, 1);
> +}
> +
> +static struct drm_bridge_funcs funcs = {
> +	.attach = lvds_codec_attach,
> +	.enable = lvds_codec_enable,
> +	.disable = lvds_codec_disable,
> +};
> +
> +static int lvds_codec_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct device_node *panel_node;
> +	struct drm_panel *panel;
> +	struct lvds_codec *lvds_codec;
> +
> +	lvds_codec = devm_kzalloc(dev, sizeof(*lvds_codec), GFP_KERNEL);
> +	if (!lvds_codec)
> +		return -ENOMEM;
> +
> +	lvds_codec->powerdown_gpio = devm_gpiod_get_optional(dev, "powerdown",
> +							     GPIOD_OUT_HIGH);
> +	if (IS_ERR(lvds_codec->powerdown_gpio))
> +		return PTR_ERR(lvds_codec->powerdown_gpio);

The driver had an error message here, any reason it got removed ?

> +
> +	panel_node = of_graph_get_remote_node(dev->of_node, 1, 0);
> +	if (!panel_node) {
> +		dev_dbg(dev, "panel DT node not found\n");
> +		return -ENXIO;
> +	}
> +
> +	panel = of_drm_find_panel(panel_node);
> +	of_node_put(panel_node);
> +	if (IS_ERR(panel)) {
> +		dev_dbg(dev, "panel not found, deferring probe\n");
> +		return PTR_ERR(panel);
> +	}
> +
> +	lvds_codec->panel_bridge = devm_drm_panel_bridge_add(dev, panel);

This was devm_drm_panel_bridge_add_typed(), do you think there's a risk
of breaking userspace ? Of course as noted in the documentation of
devm_drm_panel_bridge_add_typed() the right solution is to fix panel
drivers, but I'm still slightly worried.

Actually, could you split this patch in two, with a patch that only
renames the driver (and the symbols internally) without any functional
change, and another patch that performs the modifications ? That would
be much easier to review and discuss.

> +	if (IS_ERR(lvds_codec->panel_bridge))
> +		return PTR_ERR(lvds_codec->panel_bridge);
> +
> +	/* The panel_bridge bridge is attached to the panel's of_node,
> +	 * but we need a bridge attached to our of_node for our user
> +	 * to look up.
> +	 */
> +	lvds_codec->bridge.of_node = dev->of_node;
> +	lvds_codec->bridge.funcs = &funcs;
> +	drm_bridge_add(&lvds_codec->bridge);
> +
> +	platform_set_drvdata(pdev, lvds_codec);
> +
> +	return 0;
> +}
> +
> +static int lvds_codec_remove(struct platform_device *pdev)
> +{
> +	struct lvds_codec *lvds_codec = platform_get_drvdata(pdev);
> +
> +	drm_bridge_remove(&lvds_codec->bridge);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id lvds_codec_match[] = {
> +	{ .compatible = "lvds-encoder"  },
> +	{ .compatible = "thine,thc63lvdm83d" },
> +	{ .compatible = "lvds-decoder" },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, lvds_codec_match);
> +
> +static struct platform_driver lvds_codec_driver = {
> +	.probe	= lvds_codec_probe,
> +	.remove	= lvds_codec_remove,
> +	.driver		= {
> +		.name		= "lvds-codec",
> +		.of_match_table	= lvds_codec_match,
> +	},
> +};
> +module_platform_driver(lvds_codec_driver);
> +
> +MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>");
> +MODULE_DESCRIPTION("Driver for transparent LVDS encoders and LVDS decoders");

Maybe "LVDS encoders and decoders" ?

> +MODULE_LICENSE("GPL");

[snip]

-- 
Regards,

Laurent Pinchart



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