Hi Sakari, On Tue, Feb 21, 2023 at 02:42:31PM +0200, Sakari Ailus wrote: > On Tue, Feb 21, 2023 at 01:52:46AM +0200, Laurent Pinchart wrote: > > > > > > > + properties: > > > > > > > + bus-type: > > > > > > > + enum: [4, 5, 6] > > > > > > > > > > > > With bus-type 5, shouldn't you have the parallel interface sync signal > > > > > > polarity properties? Possibly also others if the hardware supports them. > > > > > > > > > > As far as I can tell, the hardware has fixed polarities for all signals. > > > > > Both hsync and vsync (called LINE_VALID and FRAME_VALID here) are active > > > > > high. > > > > > > > > Right, then you won't need these. > > > > > > > > What about the link-frequencies property? > > > > > > That's something I've meant to ask, should the link-frequencies property > > > be specified for parallel buses too, or only CSI-2 ? > > > > Any feedback on this ? > > Yes. > > It very likely matters there as well but probably less so than on CSI-2. > > link-frequencies isn't specific to CSI-2 either. > > > > We also need to document how a DT writer should select the link > > > frequencies. The process is complicated, saying that the property is > > > required without explaining how the values can be computed (EMC > > > constraints aside, just from a functional point of view) isn't nice. If > > > you explain this to me, I can put it in a patch :-) > > > > Or on this ? :-) > > Generally the hardware people will tell you this when it matters. :-) But > on a development board you can probably have anything the hardware > supports. > > I guess we could add a few words on this to e.g. > Documentation/driver-api/media/camera-sensor.rst . Please :-) When the sensor driver supports multiple link frequencies, and in particular a continuous range of frequencies, I want a document I can point people to precisely answer the "I have no idea about those stuff, what value do I put in my device tree?" question. It should include a clear procedure to calculate a value, not just a generic statement along the lines of "pick a value that is suitable for you". > Most drivers will support a few frequencies only and sometimes the vendor, > due to someone needing it, provides another configuration with a different > frequency. Many sensors also have datasheets that are precise enough to > calculate this yourself. -- Regards, Laurent Pinchart
