Am 15.04.25 um 15:10 schrieb Simona Vetter:

This is for devices who only want to do a vmap of the buffer, isn't it?

... it's for the vmap only case, where you might not even have a struct
device. Or definitely not a reasonable one, like maybe a faux_bus device
or some device on a bus that really doesn't do dma (e.g. spi or i2c), and
where hence dma_buf_map_attachment is just something you never ever want
to do.

Even in that case I would still suggest to at least create an attachment to let the exporter know that somebody is doing something with it's buffer.

That is also important for move notification since you can't do those without an attachment.

BTW: What is keeping a vmap alive after dropping the reservation lock? There is no pinning whatsoever as far as I can see.

I think we might want to transform obj->import_attach into a union or
tagged pointer or something like that, which can cover both cases. And
maybe a drm_gem_bo_imported_dma_buf() helper that gives you the dma_buf no
matter what if it's imported, or NULL if it's allocated on that
drm_device?

Yeah, I had the same idea before as well. Just didn't know if that was something worth looking into.

Regards,
Christian.


Cheers, Sima