On Monday 26 July 2010 18:12:55 Laurent Pinchart wrote: > On Friday 23 July 2010 17:56:02 Karicheri, Muralidharan wrote: > > Laurent, > > > > Could you explain the probe and active usage using an example such as > > below? > > > > Link1 Link2 > > input sensor -> ccdc -> video node. > > > > Assume Link2 we can have either format 1 or format 2 for capture. > > Sure. > > The probe and active formats are used to probe supported formats and > getting/setting active formats. Just to verify: we are dealing with mediabus formats here, right? One thing that I don't like is the name 'probe'. I would prefer the name 'proposed'. You propose an input format and based on that you can enumerate a list of proposed output format. I think that name fits better than 'probe' which I find confusing in this context. > > * Enumerating supported formats on the CCDC input and output would be done > with the following calls > > ENUM_FMT(CCDC input pad) > > for the input, and > > S_FMT(PROBE, CCDC input pad, format) > ENUM_FMT(CCDC output pad) > > for the output. How does ENUM_FMT know if it has to use the proposed or actual input formats? Or is it supposed to always act on proposed formats? > > Setting the probe format on the input pad is required, as the format on an > output pad usually depends on the format on input pads. > > * Trying a format on the CCDC input and output would be done with > > S_FMT(PROBE, CCDC input pad, format) > > for the input, and > > S_FMT(PROBE, CCDC input pad, format) > S_FMT(PROBE, CCDC output pad, format) > > on the output. The S_FMT call will mangle the format given format if it can't > be supported exactly, so there's no need to call G_FMT after S_FMT (a G_FMT > call following a S_FMT call will return the same format as the S_FMT call). > > * Setting the active format is done with > > S_FMT(ACTIVE, CCDC input pad, format) > S_FMT(ACTIVE, CCDC output pad, format) > > The formats will be applied to the hardware (possibly with a delay, drivers > can delay register writes until STREAMON for instance). > > Probe formats are stored in the subdev file handles, so two applications > trying formats at the same time will not interfere with each other. Active > formats are stored in the device structure, so modifications done by an > application are visible to other applications. > > Hope this helps clarifying the API. You know that I have never been happy with this approach, but I also have to admit that I haven't found a better way of doing it. Regards, Hans -- Hans Verkuil - video4linux developer - sponsored by TANDBERG, part of Cisco -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
