dma-buf: Add necessary flags for ioctls on DMA-BUF files

[obiwac]

struct files are checked for the FREAD or FWRITE flags when calling ioctl() on them. DMA-BUFs didn't have these set, without which DMA_BUF_IOCTL_SYNC cannot work.

I ran into this when working on implementing DMA_BUF_IOCTL_EXPORT_SYNC_FILE and DMA_BUF_IOCTL_IMPORT_SYNC_FILE, but I couldn't find any software on FreeBSD which actually uses the DMA_BUF_IOCTL_SYNC ioctl already which I could use to test this. Does anyone know of any?

[emersion]

I couldn't find any software on FreeBSD which actually uses the DMA_BUF_IOCTL_SYNC ioctl already which I could use to test this. Does anyone know of any?

ffmpeg does when mmap'ing DMA-BUFs:

> git grep DMA_BUF_IOCTL_SYNC
libavutil/hwcontext_drm.c:113:        ioctl(map->object[i], DMA_BUF_IOCTL_SYNC, &sync);
libavutil/hwcontext_drm.c:169:        ioctl(desc->objects[i].fd, DMA_BUF_IOCTL_SYNC, &sync_start);

I think this codepath should be triggered when using kmsgrab with a software encoder.