On Wed, Feb 01, 2017 at 10:30:57AM +0100, Philipp Zabel wrote: > On Tue, 2017-01-31 at 17:26 -0800, Steve Longerbeam wrote: > [...] > > right, need to fix that. Probably by poking the attached > > source subdev (csi or prpenc/vf) for its supported formats. > > You are right, in bayer/raw mode only one specific format should be > listed, depending on the CSI output pad format. It depends what Steve means by "source subdev". It should be the next sub-device below the bridge - if we have this setup of subdev's: ---> CSI ---> SMFC ---> IDMAC then the format configured at the SMFC's output pad is what matters, not what was configured at CSI. It's the responsibility of SMFC and CSI to make sure that their source pads are configured with a compatible format for their corresponding source pad, and it's also the sink subdev's responsibility to check that the configuration across a link is valid (possibly via v4l2_subdev_link_validate(), or a more intensive or relaxed test if required.) For example: - when CSI's source pad is configured with a RGGB output format, userspace media-ctl will also set that on SMFC's sink pad. - when SMFC's sink pad is configured, SMFC should configure it's source pad with an identical format (RGGB). - when SMFC's source pad is configured, it should refuse to change the format, because SMFC can't modify pixel the format - it's just a buffer. When starting to stream (Documentation/media/kapi/v4l2-subdev.rst) the link validation function is called, and: - the SMFC driver's link_validate function will be called to validate the CSI -> SMFC link. This allows the SMFC to be sure that there's a compatible configuration - and, since the link does not allow format conversion, it should verify that the format on the CSI's source pad is the same as SMFC's sink pad. Not only does this match what the hardware's doing, it also means that, because there's no format conversion between the CSI's hardware output and IDMAC, we don't need to care about trying to fetch the CSI's source pad configuration from the IDMAC end - we can fetch that information from our neighbour's SMFC's source pad _or_ our own sink pad if we have one. To see why this is an important, consider what the effect would be if SMFC did have the capability to change the pixel format. That means the format presented to the IDMAC block would depend on the configuration of SMFC, and the CSI's source pad format is no longer relevant to IDMAC. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
