From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: [PATCH v4 3/7] drm/tilcdc: Add support for external tda998x encoder Date: Wed, 1 Apr 2015 23:20:31 +0100 Message-ID: <20150401222030.GD4027@n2100.arm.linux.org.uk> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jyri Sarha Cc: dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org, airlied-cv59FeDIM0c@public.gmane.org, linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, bcousson-rdvid1DuHRBWk0Htik3J/w@public.gmane.org, tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org, tomi.valkeinen-l0cyMroinI0@public.gmane.org, robdclark-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, moinejf-GANU6spQydw@public.gmane.org List-Id: devicetree@vger.kernel.org On Wed, Apr 01, 2015 at 11:49:27AM +0300, Jyri Sarha wrote: > Add support for an external compontised DRM encoder. The external > encoder can be connected to tilcdc trough device tree graph binding. > The binding document for tilcdc has been updated. The current > implementation supports only tda998x encoder. > > To be able to filter out the unsupported video modes the tilcdc driver > needs to hijack the external connectors helper functions. The tilcdc > installes new helper functions that are otherwise identical to > orignals, but the mode_valid() call-back check the mode first localy, > before calling the original call-back. The tilcdc dirver restores the > original helper functions before it is unbound from the external > device. This is where the DRM model is weak - we don't really have a way to say "this is the set of CRTCs which /can/ be associated with this connector, can any of the CRTCs accept this mode?" and eliminate modes which fail that check. This problem seems to be one which recurrs, so I wonder if it's something which ought to be solved properly. It's made slightly more difficult because we don't really know which connectors could be associated with which CRTCs - that information is stored at the encoder level (with the encoders possible_crtcs), and I'm not sure we have a way for generic DRM code to know which encoders could be associated with which connectors. -- FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html