linux-kernel - Re: [v14, 01/17] drm: bridge: analogix/dp: split exynos dp driver to bridge directory

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Date:	Thu, 31 Mar 2016 11:56:02 +0200
From:	Thierry Reding <treding@...dia.com>
To:	Guenter Roeck <linux@...ck-us.net>
CC:	Yakir Yang <ykk@...k-chips.com>, Inki Dae <inki.dae@...sung.com>,
	"Andrzej Hajda" <a.hajda@...sung.com>,
	Joonyoung Shim <jy0922.shim@...sung.com>,
	Seung-Woo Kim <sw0312.kim@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Jingoo Han <jingoohan1@...il.com>,
	"Krzysztof Kozlowski" <k.kozlowski@...sung.com>,
	Rob Herring <robh+dt@...nel.org>,
	"Heiko Stuebner" <heiko@...ech.de>,
	Mark Yao <mark.yao@...k-chips.com>,
	Russell King <linux@....linux.org.uk>, <djkurtz@...omium.org>,
	Sean Paul <seanpaul@...omium.org>,
	Kukjin Kim <kgene@...nel.org>,
	Kumar Gala <galak@...eaurora.org>, <emil.l.velikov@...il.com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Gustavo Padovan <gustavo.padovan@...labora.co.uk>,
	Kishon Vijay Abraham I <kishon@...com>,
	Pawel Moll <pawel.moll@....com>, <ajaynumb@...il.com>,
	<robherring2@...il.com>, <javier@....samsung.com>,
	Andy Yan <andy.yan@...k-chips.com>,
	<dri-devel@...ts.freedesktop.org>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	<linux-samsung-soc@...r.kernel.org>,
	<linux-rockchip@...ts.infradead.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	Douglas Anderson <dianders@...omium.org>
Subject: Re: [v14, 01/17] drm: bridge: analogix/dp: split exynos dp driver to
 bridge directory

On Wed, Mar 30, 2016 at 01:32:04PM -0700, Guenter Roeck wrote:
> Hi,
> 
> On Mon, Feb 15, 2016 at 07:09:36PM +0800, Yakir Yang wrote:
> > Split the dp core driver from exynos directory to bridge directory,
> > and rename the core driver to analogix_dp_*, rename the platform
> > code to exynos_dp.
> > 
> > Beside the new analogix_dp driver would export six hooks.
> > "analogix_dp_bind()" and "analogix_dp_unbind()"
> > "analogix_dp_suspned()" and "analogix_dp_resume()"
> > "analogix_dp_detect()" and "analogix_dp_get_modes()"
> > 
> > The bind/unbind symbols is used for analogix platform driver to connect
> > with analogix_dp core driver. And the detect/get_modes is used for analogix
> > platform driver to init the connector.
> > 
> > They reason why connector need register in helper driver is rockchip drm
> > haven't implement the atomic API, but Exynos drm have implement it, so
> > there would need two different connector helper functions, that's why we
> > leave the connector register in helper driver.
> > 
> > Signed-off-by: Yakir Yang <ykk@...k-chips.com>
> > 
> [ ... ]
> 
> > diff --git a/drivers/gpu/drm/bridge/analogix/Makefile b/drivers/gpu/drm/bridge/analogix/Makefile
> > new file mode 100644
> > index 0000000..9107b86
> > --- /dev/null
> > +++ b/drivers/gpu/drm/bridge/analogix/Makefile
> > @@ -0,0 +1 @@
> > +obj-$(CONFIG_DRM_ANALOGIX_DP) += analogix_dp_core.o analogix_dp_reg.o
> 
> This results in the following build errors if DRM_ANALOGIX_DP
> is configured as module.
> 
> ERROR: "analogix_dp_start_video" [drivers/gpu/drm/bridge/analogix/analogix_dp_core.ko] undefined!
> ERROR: "analogix_dp_get_lane0_link_training" [drivers/gpu/drm/bridge/analogix/analogix_dp_core.ko] undefined!
> ERROR: "analogix_dp_get_lane1_link_training" [drivers/gpu/drm/bridge/analogix/analogix_dp_core.ko] undefined!
> ERROR: "analogix_dp_get_lane2_link_training" [drivers/gpu/drm/bridge/analogix/analogix_dp_core.ko] undefined!
> ERROR: "analogix_dp_get_lane3_link_training" [drivers/gpu/drm/bridge/analogix/analogix_dp_core.ko] undefined!
> ERROR: "analogix_dp_get_lane_count" [drivers/gpu/drm/bridge/analogix/analogix_dp_core.ko] undefined!
> ERROR: "analogix_dp_get_link_bandwidth" [drivers/gpu/drm/bridge/analogix/analogix_dp_core.ko] undefined!
> 
> [ and so on ]

Ugh... most of these functions shouldn't be there in the first place. We
have helpers in the core that already do this. Most of the functionality
is duplicated in this driver.

I realize that this is a problem that existed in the Exynos DP driver,
but somebody really ought to rewrite those parts to make use of the DRM
DP helpers.

Thierry

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