On 05/30/2013 05:21 AM, Laurent Pinchart wrote: > Hi Sylwester, > > On Saturday 25 May 2013 16:11:52 Sylwester Nawrocki wrote: >> On 05/25/2013 11:17 AM, Prabhakar Lad wrote: [...] >>>>> And for synchronisation method on the analog part we could perhaps >>>>> define 'component-sync' or similar property that would enumerate all >>>>> possible synchronisation methods. We might as well use separate >>>>> boolean properties, but I'm a bit concerned about the increasing >>>>> number of properties that need to be parsed for each parallel video >>>>> bus "endpoint". >>> >>> I am not clear on it can please elaborate more on this. >> >> I thought about two possible options: >> >> 1. single property 'component-sync' or 'video-sync' that would have values: >> >> #define VIDEO_SEPARATE_SYNC 0x01 >> #define VIDEO_COMPOSITE_SYNC 0x02 >> #define VIDEO_SYNC_ON_COMPOSITE 0x04 >> #define VIDEO_SYNC_ON_GREEN 0x08 >> #define VIDEO_SYNC_ON_LUMINANCE 0x10 >> >> And we could put these definitions into a separate header, e.g. >> <dt-bindings/video-interfaces.h> >> >> Then in a device tree source file one could have, e.g. >> >> video-sync = <VIDEO_SYNC_ON_GREEN>; >> >> >> 2. Separate boolean property for each video sync type, e.g. >> >> "video-composite-sync" >> "video-sync-on-composite" >> "video-sync-on-green" >> "video-sync-on-luminance" >> >> Separate sync, with separate VSYNC, HSYNC lines, would be the default, when >> none of the above is specified and 'vsync-active', 'hsync-active' properties >> are present. > > I prefer 1. over 2. > >> However, I suppose the better would be to deduce the video synchronisation >> method from the sync signal polarity flags. Then, for instance, when an >> endpoint node contains "composite-sync-active" property the parser would >> determine the "composite sync" synchronisation type is used. >> >> Thus it might make sense to have only following integer properties (added >> as needed): >> >> composite-sync-active >> sync-on-green-active >> sync-on-comp-active >> sync-on-luma-active >> >> This would allow to specify polarity of each signal and at the same time >> the parsing code could derive synchronisation type. A new field could be >> added to struct v4l2_of_parallel_bus, e.g. sync_type and it would be filled >> within v4l2_of_parse_endpoint(). >> >> What do you think ? > > My gut feeling is that we should have separate properties for the video sync > type and the synchronization signals polarities. We could have a chip that > supports sync-on-green on the analog (input) side and outputs separate hsync > and vsync signals only on the digital (output) side. There would be no sync- > on-green polarity in that case. Yes, agreed. I've had some doubts that using single DT property for defining really 2 distinct H/W properties like this might not be flexible enough. The option 1. seems most correct then. Regards, Sylwester -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
