[PATCH] drm: Add drm_bridge

[Alex Deucher]

On Fri, Aug 9, 2013 at 9:19 AM, Sean Paul <seanpaul at chromium.org> wrote:
> On Thu, Aug 8, 2013 at 8:36 PM, Daniel Vetter <daniel at ffwll.ch> wrote:
>> On Thu, Aug 8, 2013 at 11:03 PM, Sean Paul <seanpaul at chromium.org> wrote:
>>> This patch adds the notion of a drm_bridge. A bridge is a chained
>>> device which hangs off an encoder. The drm driver using the bridge
>>> should provide the association between encoder and bridge. Once a
>>> bridge is associated with an encoder, it will participate in mode
>>> set, dpms, and optionally connection detection.
>>>
>>> Since a connector may not be able to determine the connection state
>>> downstream of the bridge, bridges may implement detect() which will take
>>> precedence over connector detect() if the bridge is already attached
>>> to an encoder and that encoder is already attached to the connector.
>>> In practical terms, this requires the drm driver to make these
>>> associations at init time, which is fine for SoC applications where
>>> this link is static.
>>>
>>> Signed-off-by: Sean Paul <seanpaul at chromium.org>
>>
>> A few comments below. I think overall any such infrastructure simply
>> needs to demonstrate viability on a few drivers, that makes it much
>> simpler to check whether the interfaces make sense.
>
> Thanks for your feedback, Daniel.
>
> As mentioned by Stephane and Rob, there are a few drivers already
> using this. In the ChromeOS tree, we have 2 simple DP->LVDS bridges
> which quite frankly aren't terribly interesting atm, and we'll be
> converting an HDMI->myDP bridge in a couple of weeks (time permitting,
> of course).

radeon also uses DP->LVDS and DP->VGA bridges on a number of systems.
It currently uses a driver specific hack, but it could probably be
converted to use the bridge infrastructure.

Alex