linux-kernel - Re: [RFC PATCH 1/2] drm/panel: add support for simple-panel description definition using DT

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Date:	Mon, 12 May 2014 15:02:31 +0200
From:	Boris BREZILLON <boris.brezillon@...e-electrons.com>
To:	Thierry Reding <thierry.reding@...il.com>
CC:	Randy Dunlap <rdunlap@...radead.org>,
	David Airlie <airlied@...ux.ie>,
	Jean-Jacques Hiblot <jjhiblot@...phandler.com>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 1/2] drm/panel: add support for simple-panel description
 definition using DT


On 09/05/2014 16:16, Boris BREZILLON wrote:
> Currently, the only way to add new panel descriptions to the simple panel
> driver is to add new entries in the platform_of_match table.
>
> Add support for panel description retrieval from the DT.
>
> Signed-off-by: Boris BREZILLON <boris.brezillon@...e-electrons.com>
> ---
>  drivers/gpu/drm/panel/Kconfig        |  1 +
>  drivers/gpu/drm/panel/panel-simple.c | 70 ++++++++++++++++++++++++++++++++++++
>  2 files changed, 71 insertions(+)
>
> diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
> index 4ec874d..4fe3d48 100644
> --- a/drivers/gpu/drm/panel/Kconfig
> +++ b/drivers/gpu/drm/panel/Kconfig
> @@ -1,6 +1,7 @@
>  config DRM_PANEL
>  	bool
>  	depends on DRM
> +	select VIDEOMODE_HELPERS
>  	help
>  	  Panel registration and lookup framework.
>  
> diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
> index 309f29e..fcf648d 100644
> --- a/drivers/gpu/drm/panel/panel-simple.c
> +++ b/drivers/gpu/drm/panel/panel-simple.c
> @@ -33,6 +33,10 @@
>  #include <drm/drm_mipi_dsi.h>
>  #include <drm/drm_panel.h>
>  
> +#include <video/display_timing.h>
> +#include <video/of_display_timing.h>
> +#include <video/videomode.h>
> +
>  struct panel_desc {
>  	const struct drm_display_mode *modes;
>  	unsigned int num_modes;
> @@ -168,6 +172,61 @@ static const struct drm_panel_funcs panel_simple_funcs = {
>  	.get_modes = panel_simple_get_modes,
>  };
>  
> +static struct panel_desc *of_panel_desc_init(struct device *dev)
> +{
> +	struct display_timings *timings;
> +	struct panel_desc *desc;
> +	u32 width, height;
> +	int err;
> +	int i;
> +
> +	err = of_property_read_u32(dev->of_node, "width", &width);
> +	if (err)
> +		return ERR_PTR(err);
> +
> +	err = of_property_read_u32(dev->of_node, "height", &height);
> +	if (err)
> +		return ERR_PTR(err);
> +
> +	desc = devm_kzalloc(dev, sizeof(*desc), GFP_KERNEL);
> +	if (!desc)
> +		return ERR_PTR(-ENOMEM);
> +
> +	timings = of_get_display_timings(dev->of_node);
> +	if (timings) {
> +		struct drm_display_mode *modes =
> +				devm_kzalloc(dev,
> +					     timings->num_timings *
> +					     sizeof(*desc->modes),
> +					     GFP_KERNEL);
> +
> +		if (!modes)
> +			return ERR_PTR(-ENOMEM);
> +
> +		for (i = 0; i < timings->num_timings; i++) {
> +			struct videomode vm;
> +
> +			if (videomode_from_timings(timings, &vm, i))
> +				break;
> +
> +			drm_display_mode_from_videomode(&vm, modes + i);
> +
> +			modes[i].type = DRM_MODE_TYPE_DRIVER;
> +
> +			if (timings->native_mode == i)
> +				modes[i].type |= DRM_MODE_TYPE_PREFERRED;
> +			desc->num_modes++;
> +		}

Oops, I forgot to add:
                          desc->modes = modes;

> +
> +		kfree(timings);
> +	}
> +
> +	desc->size.width = width;
> +	desc->size.height = height;
> +
> +	return desc;
> +}
> +
>  static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
>  {
>  	struct device_node *backlight, *ddc;
> @@ -178,6 +237,17 @@ static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
>  	if (!panel)
>  		return -ENOMEM;
>  
> +	if (!desc) {
> +		desc = of_panel_desc_init(dev);
> +		/*
> +		 * Do not fail on DT panel desc retrieval error because
> +		 * some systems do not need a panel description to work
> +		 * properly.
> +		 */
> +		if (IS_ERR(desc))
> +			desc = NULL;
> +	}
> +
>  	panel->enabled = false;
>  	panel->desc = desc;
>  

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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