Re: [PATCH v2 2/4] dma-buf: Document revoke semantics

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

On Sun, 2026-01-18 at 14:08 +0200, Leon Romanovsky wrote:
> From: Leon Romanovsky <leonro@nvidia.com>
> 
> Document a DMA-buf revoke mechanism that allows an exporter to
> explicitly
> invalidate ("kill") a shared buffer after it has been handed out to
> importers. Once revoked, all further CPU and device access is
> blocked, and
> importers consistently observe failure.

See previous comment WRT this.

> 
> This requires both importers and exporters to honor the revoke
> contract.
> 
> For importers, this means implementing .invalidate_mappings() and
> calling
> dma_buf_pin() after the DMA‑buf is attached to verify the exporter’s
> support
> for revocation.

Why would the importer want to verify the exporter's support for
revocation? If the exporter doesn't support it, the only consequence
would be that invalidate_mappings() would never be called, and that
dma_buf_pin() is a NOP. Besides, dma_buf_pin() would not return an
error if the exporter doesn't implement the pin() callback?

Or perhaps I missed a prereq patch?

Thanks,
Thomas