Hi everybody, Many of our embedded systems I deal with are equipped with (too) smart camera sensors (devices) which use MIPI-CSI bus to send already compressed image data. Usually the media bus is used with camera for transmitting raw image data, where it's easy to calculate target memory buffer size given the pixel resolution, bus width and number of bus samples per pixel.
However when compressed formats come into play, there is no standard way to obtain information from a subdev how much data it is going to transmit per single frame. In other words MIPI-CSI receiver can't know how much memory it should allocate for MIPI-CSI transmitter to proceed. The following change set adds g_framesamples callback to the subdev video operations set, so the host drivers can query subdev for memory requirements per specific format. I have added media bus pixel format as an argument because the host may need to know number of samples per frame' if user space issues VIDIOC_TRY_FMT, at this time pixel format at MIPI-CSI transmitter subdev might not be set yet. I have also been preparing patches utilising '__u32 framesamples' field added to struct v4l2_mbus_framefmt. Extending v4l2_mbus_framefmt data structure allows to associate frame length with pads, similarly as it's done with media bus pixel format. But if would force application to set proper framesamples value at each pad, I suppose it could be done only for compressed formats, then the host driver would validate the values before actually starting streaming. Any critics and suggestions are welcome :-) Sylwester Nawrocki (3): v4l: Add new g_framesamples subdev video operation s5p-fimc: Add g_framesamples subdev operation support m5mols: Add g_framesamples operation support drivers/media/video/m5mols/m5mols.h | 2 + drivers/media/video/m5mols/m5mols_capture.c | 4 ++ drivers/media/video/m5mols/m5mols_core.c | 16 ++++++- drivers/media/video/m5mols/m5mols_reg.h | 2 + drivers/media/video/s5p-fimc/fimc-capture.c | 63 +++++++++++++++++++++++++-- drivers/media/video/s5p-fimc/fimc-core.c | 11 ++++- drivers/media/video/s5p-fimc/fimc-core.h | 9 +++- include/media/v4l2-subdev.h | 6 +++ 8 files changed, 103 insertions(+), 10 deletions(-) -- Regards, Sylwester -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
