Re: [PATCH] drm/exynos: Fix PTN3460 dependency

From: Inki Dae <inki.dae@samsung.com>
To: Thierry Reding <thierry.reding@gmail.com>
Cc: Kukjin Kim <kgene.kim@samsung.com>,
	Seung-Woo Kim <sw0312.kim@samsung.com>,
	Alexander Graf <agraf@suse.de>,
	dri-devel@lists.freedesktop.org,
	Kyungmin Park <kyungmin.park@samsung.com>,
	Jean Delvare <jdelvare@suse.de>
Subject: Re: [PATCH] drm/exynos: Fix PTN3460 dependency
Date: Thu, 22 May 2014 20:27:02 +0900	[thread overview]
Message-ID: <537DDF06.7030206@samsung.com> (raw)
In-Reply-To: <20140521155059.GP2014@ulmo>

On 2014년 05월 22일 00:51, Thierry Reding wrote:
> On Tue, May 20, 2014 at 11:15:25AM +0200, Jean Delvare wrote:
>> The following configuration options combination:
>>
>> CONFIG_DRM_EXYNOS_DP=y
>> CONFIG_DRM_PTN3460=m
>>
>> currently leads to the following linker failure:
>>
>> drivers/built-in.o: In function `exynos_drm_attach_lcd_bridge':
>> .../drivers/gpu/drm/exynos/exynos_dp_core.c:1004:
>> undefined reference to `ptn3460_init'
>>
>> This is because ptn3460_init can't be implemented in a module while
>> its caller is built into the kernel. So add the proper dependency in
>> Kconfig so that the above can't happen.
>>
>> I moved DRM_PTN3460 earlier in Kconfig, next to the I2C helper module
>> section, so that the user has a chance to select it before moving to
>> the Exynos-specific section.
>>
>> IMHO the proper way to solve the problem would be to turn ptn3460 into
>> a clean I2C driver, similar to the other I2C helper chip drivers. It's
>> the only way to not sink into impossible-to-guess dependencies. Then
>> ptn3460 could even be moved together with the other I2C helper chip
>> drivers.
> 
> FWIW, various ideas have been discussed to solve this problem. The most
> recent agreement I think was to create a registry for bridge drivers to
> register DRM bridge objects against and allow drivers to look them up.
> That way we can get rid of the various *_init() functions that currently
> need to be called directly from within DRM drivers.
> 

I tend to prefer integrated drm_bridge based on drm_panel infrastructure
so that bridge drivers can use Linux driver-model. But it seems not easy
to reach a consensus on it.

picked it up.

Thanks,
Inki Dae

> I'm not aware of anybody working on this currently, hence I think this
> is an appropriate fix in the meantime:
> 
> Reviewed-by: Thierry Reding <treding@nvidia.com>
> 
> 
> 
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