Re: [PATCH 01/19] User-space API definition

[Miloslav Trmac <mitr@redhat.com>]

----- "Herbert Xu" <herbert@gondor.hengli.com.au> wrote:
> Thanks for the updated patch-set.  It does indeed fulfil some
> of the requirements raised earlier.
> 
> However, as far as I can see this still does not address the
> extensibility.  For example, say we want add an interface to
> allow the xoring of two arbitrary data streams using DMA offload,
> this interface would make that quite awkward.
I don't think this would be a problem:

- Expose the xoring as a crypto_tfm, with the usual crypto API string identifier
  (this is supposed to be a crypto API interface, not a generic interface
  to the platform DMA controller, after all).

- Check to see if the operation can be supported using the existing
  attributes, add attributes if necessary.

  In this case, NCR_UPDATE_INPUT_DATA can be used for the read-only
  stream and NCR_UPDATE_OUTPUT_BUFFER for the read-write steram.

- If this is an entirely new crypto transform type, add support to
  the session interface.

  In this case, this would probably mean adding NCR_OP_COMBINE (or
  something similar); SESSION_INIT would only allocate the tfm,
  SESSION_UPDATE would be used for handling blocks of data as they
  come and go.

The interface would have to be extended, but the extension would be completely backward-compatible and the additions to the interface would probably be smaller than the additions to the internal crypto API.  Notably no new ioctl()s would be needed.
    Mirek