Hi Ian, On Tue, 12 Aug 2014, Ian Molton wrote: > rcar_vin_get_formats() > > Can anyone explain to me what on earth this function is trying to > achieve? I'm finding it rather impenetrable, and it works for me on one > driver (adv7180) but not with another (modified 7612 driver). > > It appears that its doing some sort of magic with the builtin array of > formats, to allow the 7180 driver to select a YUV mode?? but I cant for > the life of me understand what. I'm fairly new to v4l2, so I dont really > know whats legit and what isnt. particularly, the code appears to abuse > one "code" to provide several (incompatible?) formats. That function is adding support for VIN own format conversions. V4L2 drivers get requests from the user space to provide data to the application in one of V4L2_PIX_FMT_* formats. Those formats define how data is organised in memory buffers. Camera sensors however send data to camera host adapters, like VIN, over a bus, using one of V4L2_MBUS_FMT_* formats. The camera host then uses DMA to transfer the data into a memory buffer. In the most trivial case the camera interface consists of 8 or 16 data lines and the host simply stores bytes or 16-bit words directly into memory. This is called in the soc-camera framework a pass-through mode. However, many hosts additionally provide several ways to convert the data in real time and store them into memore in one of several formats. In soc-camera this is implemented, using translation tables. This is exactly what this function does. Specifically it specifies, that if the sensor supports one of case V4L2_MBUS_FMT_YUYV8_1X16: case V4L2_MBUS_FMT_YUYV8_2X8: case V4L2_MBUS_FMT_YUYV10_2X10: formats, the VIN can convert them to any of the formats, specified in the rcar_vin_formats[] array. And since it can happen, that the sensor supports several of the above V4L2_MBUS_FMT_* formats, care is taken to attach the additional table of generated formats only once. Thanks Guennadi > Help? > > -- > Ian Molton <ian.molton@xxxxxxxxxxxxxxx> > -- > 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 > -- 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
