Hi Carl, > > > besides this, ask a dumb question. > > > How we retrieve the pat_index from a shared resource though dma_buf fd? > > > maybe we need to know whether it could be CPU cached if we want map it. > > > Of course, looks there are no real usage to access it though CPU. > > > Just use it directly without any pat related options ? > > > > I am not understanding. Do you want to ask the PAT table to the driver? Are > > you referring to the CPU PAT index? > > > > In any case, if I understood correctly, you don't necessarily always need to > > set the PAT options and the cache options will fall into the default values. > > > > Please let me know if I haven't answered the question. > > > > If mesa create a resource , then use DRM_IOCTL_PRIME_HANDLE_TO_FD convert it to a dma fd. > Then share it to media, media use DRM_IOCTL_PRIME_FD_TO_HANDLE convert it to a gem bo. > But media does not know the PAT index , because mesa create it and set it. > So, if media want to call DRM_IOCTL_I915_GEM_MMAP_OFFSET, media does not know whether it could be WB. That's a good point. To be honest I am not really sure how this is handled. Fei, Jordan? Do you have suggestion here? Andi
