On Wed, Sep 16, 2020 at 11:53:59AM +0200, Daniel Vetter wrote: > But within the driver, we generally need thousands of these, and that > tends to bring fd exhaustion problems with it. That's why all the private > buffer objects which aren't shared with other process or other drivers are > handles only valid for a specific fd instance of the drm chardev (each > open gets their own namespace), and only for ioctls done on that chardev. > And for mmap we assign fake (but unique across all open fd on it) offsets > within the overall chardev. Hence all the pgoff mangling and re-mangling. Are they still unique struct files? Just without a fdno? > Hence why we'd like to be able to forward aliasing mappings and adjust the > file and pgoff, while hopefully everything keeps working. I thought this > would work, but Christian noticed it doesn't really. It seems reasonable to me that the dma buf should be the owner of the VMA, otherwise like you say, there is a big mess attaching the custom vma ops and what not to the proper dma buf. I don't see anything obviously against this in mmap_region() - why did Chritian notice it doesn't really work? Jason
