Hi All, I have hardware that does some sort of image manipulation. The hardware takes 2 inputs. - image buffer - config param buffer and generates one output which is also an image buffer. The input and output images formats fall under standard image definitions of V4L2 like various YUV/RGB formats (interleaved or multiplanar). The config param buffer is kind of like a set of instructions for the hardware that needs to be passed with every input and output image which tells the hardware how to process the image. The hardware will be given different input images and output images every time and possibly different config param buffers too (in some cases). The config param buffers may have variable sizes too based on the nature of processing for that frame, but input and output images are fixed in size for a given context. I should also mention that the config param buffers are a few KBs in size so zero copy is a requirement. The config params buffers are written by userspace (possibly also driver in kernel space) and read by hardware. Here were two mechanisms I had in mind while trying to design a V4L2 M2M driver for this hardware. - Use a custom multiplanar input format where one plane is a config param buffer with remaining planes for input images (in case the input image is also multiplanar). - Use dmabuf heaps to allocate config param buffer. Tie this config param buffer fd to an input buffer (using request API). Driver would have to attach the config param buffer dmabuf fd, use it and detach. Any comments/concerns about the above two mechanisms ? Any other better ideas ? Are there any existing V4L2 M2M mechanisms present to deal with per frame param buffers that are also zero copy ? Is the media request API able to do zero copy for setting compound controls for large (several KBs) compound controls ? (making the above dmabuf heap approach unnecessary) -- Regards, Karthik Poduval
