linux-kernel - Re: [PATCH] drm: Add drm.edid_quirk

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Date:   Wed, 15 Aug 2018 16:05:28 +0300
From:   Jani Nikula <jani.nikula@...ux.intel.com>
To:     Keith Packard <keithp@...thp.com>, linux-kernel@...r.kernel.org,
        Dave Airlie <airlied@...hat.com>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     Keith Packard <keithp@...thp.com>, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] drm: Add drm.edid_quirk_param module parameter

On Wed, 08 Aug 2018, Keith Packard <keithp@...thp.com> wrote:
> This parameter allows the set of EDID quirks to be changed at
> runtime. The syntax is
>
> 	vendor/product/quirks,vendor/product/quirks,...
>
> where vendor is the three-letter EDID vendor value, product is the
> EDID product id which may be prefixed with 0x to for hex instead of
> decimal values and quirks is the replacement quirks value from the
> list in drm_edid.c.

Why?

I guess if we want to manage quirks from userspace, we should work to
provide an interface udev can use.

BR,
Jani.

>
> Signed-off-by: Keith Packard <keithp@...thp.com>
> ---
>  drivers/gpu/drm/drm_edid.c | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 5dc742b27ca0..63b4587faddd 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -98,6 +98,12 @@ struct detailed_mode_closure {
>  #define LEVEL_GTF2	2
>  #define LEVEL_CVT	3
>  
> +#define EDID_QUIRK_PARAM_LEN	256
> +static char edid_quirk_param[EDID_QUIRK_PARAM_LEN];
> +module_param_string(edid_quirk_param, edid_quirk_param, sizeof(edid_quirk_param), 0644);
> +MODULE_PARM_DESC(edid_quirk_param, "Extra EDID quirks, "
> +		 "format is 'vendor/product/quirks;...' ");
> +
>  static const struct edid_quirk {
>  	char vendor[4];
>  	int product_id;
> @@ -1774,8 +1780,24 @@ static bool edid_vendor(const struct edid *edid, const char *vendor)
>  static u32 edid_get_quirks(const struct edid *edid)
>  {
>  	const struct edid_quirk *quirk;
> +	const char *q;
>  	int i;
>  
> +	for (q = edid_quirk_param; q && *q; q = strchr(q, ',')) {
> +		char 	vendor[4];
> +		int	product_id;
> +		int	quirks;
> +
> +		while (*q == ',')
> +			q++;
> +
> +		if (sscanf(q, "%3s/%i/%i", vendor, &product_id, &quirks) == 3) {
> +			if (edid_vendor(edid, vendor) &&
> +			    (EDID_PRODUCT_ID(edid) == product_id))
> +				return quirks;
> +		}
> +	}
> +
>  	for (i = 0; i < ARRAY_SIZE(edid_quirk_list); i++) {
>  		quirk = &edid_quirk_list[i];

-- 
Jani Nikula, Intel Open Source Graphics Center