linux-kernel - Re: [PATCH v3 1/3] drm/exynos: Get HDMI version from device tree

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Date:	Tue, 5 Feb 2013 16:37:42 -0800
From:	Sean Paul <seanpaul@...omium.org>
To:	Stephen Warren <swarren@...dotorg.org>
Cc:	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org,
	devicetree-discuss@...ts.ozlabs.org,
	dri-devel@...ts.freedesktop.org,
	Tomasz Stanislawski <t.stanislaws@...sung.com>,
	"kgene.kim" <kgene.kim@...sung.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Tomasz Figa <tomasz.figa@...il.com>,
	InKi Dae <inki.dae@...sung.com>,
	Sylwester Nawrocki <sylvester.nawrocki@...il.com>,
	Olof Johansson <olofj@...omium.org>,
	RAHUL SHARMA <rahul.sharma@...sung.com>
Subject: Re: [PATCH v3 1/3] drm/exynos: Get HDMI version from device tree

On Tue, Feb 5, 2013 at 4:22 PM, Stephen Warren <swarren@...dotorg.org> wrote:
> n 02/05/2013 04:42 PM, Sean Paul wrote:
>> Use the compatible string in the device tree to determine which
>> registers/functions to use in the HDMI driver. Also changes the
>> references from v13 to 4210 and v14 to 4212 to reflect the IP
>> block version instead of the HDMI version.
>
>> diff --git a/Documentation/devicetree/bindings/drm/exynos/hdmi.txt b/Documentation/devicetree/bindings/drm/exynos/hdmi.txt
>
> Binding looks sane to me.
>
>> diff --git a/drivers/gpu/drm/exynos/exynos_hdmi.c b/drivers/gpu/drm/exynos/exynos_hdmi.c
>
>>  #ifdef CONFIG_OF
>>  static struct of_device_id hdmi_match_types[] = {
>>       {
>> -             .compatible = "samsung,exynos5-hdmi",
>> -             .data   = (void *)HDMI_TYPE14,
>> +             .compatible = "samsung,exynos4-hdmi",
>>       }, {
>>               /* end node */
>>       }
>
> Why not fill in all the "base" compatible values there (I think you need
> this anyway so that DTs don't all have to be compatible with
> samsung,exynos4-hdmi), with .data containing the HDMI_VER_EXYNOS*
> values, then ...
>

At the moment, all DTs have to be compatible with exynos4-hdmi since
it provides the base for the current driver. The driver uses 4210 and
4212 to differentiate between different register addresses and
features, but most things are just exynos4-hdmi compatible.

>> @@ -2218,17 +2217,18 @@ static int hdmi_probe(struct platform_device *pdev)
>
>> +
>> +     if (of_device_is_compatible(dev->of_node, "samsung,exynos4210-hdmi"))
>> +             hdata->version |= HDMI_VER_EXYNOS4210;
>> +     if (of_device_is_compatible(dev->of_node, "samsung,exynos4212-hdmi"))
>> +             hdata->version |= HDMI_VER_EXYNOS4212;
>> +     if (of_device_is_compatible(dev->of_node, "samsung,exynos5250-hdmi"))
>> +             hdata->version |= HDMI_VER_EXYNOS5250;
>
> Instead of that, do roughly:
>
>     match = of_match_device(hdmi_match_types, &pdev->dev);
>     if (match)
>         hdata->version |= (int)match->data;
>
> That way, it's all table-based. Any future additions to
> hdmi_match_types[] won't require another if statement to be added to
> probe().

I don't think it's that easy. of_match_device returns the first match
from the device table, so I'd still need to iterate through the
matches. I could still break this out into a table, but I don't think
of_match_device is the right way to probe it.

Sean
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