Hi Laurent, On 10/12/2018 04:01 PM, Laurent Pinchart wrote: > Hello Vladimir, > > On Friday, 12 October 2018 14:47:52 EEST Kieran Bingham wrote: >> On 12/10/18 11:58, Vladimir Zapolskiy wrote: [snip] >> Essentially they are multi purpose buses - which do not yet have a home. >> We have used media as a home because of our use case. >> >> The use case whether they transfer frames from a camera or to a display >> are of course closely related, but ultimately covered by two separate >> subsystems at the pixel level (DRM vs V4L, or other for other data) >> >> Perhaps as they are buses - on a level with USB or I2C (except they can >> of course carry I2C or Serial as well as 'bi-directional video' etc ), >> they are looking for their own subsystem. >> >> Except I don't think we don't want to add a new subsystem for just one >> (or two) devices... > > I'm not sure a new subsystem is needed. As you've noted there's an overlap > between drivers/media/ and drivers/gpu/drm/ in terms of supported hardware. > We even have a devices supported by two drivers, one in drivers/media/ and > one in drivers/gpu/drm/ (I'm thinking about the adv7511 in particular). > This is a well known issue, and so far nothing has been done in mainline > to try and solve it. I agree that there's an overlap between drivers/media/ and drivers/gpu/drm/, formally a hypothetical (sic!) DS90Ux9xx video bridge cell driver should be added into both subsystems also, and the actual driver of two should be selected in runtime. I call such a driver 'hypothetical', because in fact I don't have it, and I'm not so sure that its existence is justified, but that's only because DS90Ux9xx video bridge functionality is _transparent_, it does not have any controls literally, but it is a pure luck eventually. So, as I've stated in my cover letter, I can misuse yours 'lvds-encoder' driver only for the purpose of establishing a mediated link between an LVDS controller and a panel over a serializer-deserializer pair. > Trying to find another home in drivers/mfd/ to escape from the problem isn't a > good solution in my opinion. The best option from a Linux point of view would > be to unify V4L2 and DRM/KMS when it comes to bridge support, but that's a > long way down the road (I won't complain if you want to give it a go though > :-)). I return you a wider smile :) > As your use cases are display, focused, I would propose to start with > drivers/gpu/drm/bridge/, and leave the problem of camera support for first > person who will have such a use case. Frankly speaking I would like to start from copy-pasting your 'lvds-encoder' driver into an 'absolutely-transparent-video-bridge' driver with no LVDS or 'encoder' specifics, adding just a new compatible may suffice, if the driver is renamed/redefined. PS, I remember I owe you a reference OF snippet of data path to a panel. -- Best wishes, Vladimir
