Hi Randy, On Tue, 29 Nov 2022 at 10:11, Hsia-Jun Li <randy.li@xxxxxxxxxxxxx> wrote: > Currently, we assume all the pixel formats are multiple planes, devices > could support each component has its own memory plane. > But that may not apply for any device in the world. We could have a > device without IOMMU then this is not impossible. > > Besides, when we export an handle through the PRIME, the upstream > device(likes a capture card or camera) may not support non-contiguous > memory. It would be better to allocate the handle in contiguous memory > at the first time. > > We may think the memory allocation is done in user space, we could do > the trick there. But the dumb_create() sometimes is not the right API > for that. > > "Note that userspace is not allowed to use such objects for render > acceleration - drivers must create their own private ioctls for such a > use case." > "Note that dumb objects may not be used for gpu acceleration, as has > been attempted on some ARM embedded platforms. Such drivers really must > have a hardware-specific ioctl to allocate suitable buffer objects." > > We need to relay on those device custom APIs then. It would be helpful > for their library to calculate the right size for contiguous memory. It > would be useful for the driver supports rendering dumb buffer as well. As a buffer can only have a single modifier, this isn't practical. Contiguous needs to be negotiated separately and out of band. See e.g. dma-heaps for this. Cheers, Daniel
