Can crypto API provide information about hw acceleration?

From: David Sterba
Date: Tue May 14 2019 - 12:34:30 EST


Q: is there a way to query the crypto layer whether a given algorithm
(digest, crypto) is accelerated by the driver?

This information can be used to decide if eg. a checksum should can be
calculated right away or offloaded to a thread. This is done in btrfs,

At this moment it contains a static check for a cpu feature, and only
for x86. I briefly searched the arch/ directory for implementations of
crc32c that possibly use hw aid and there are several of them. Adding a
static check a-la x86 for the other architectures (arm, ppc, mips,
sparc, s390) is wrong, so I'm looking for a clean solution.

The struct shash_alg definition of the algorithms does not say anything
about the acceleration. The closest thing is the cra_priority, but I
don't know if this is reliable information. The default implementations
seem to have 100, and acceleated 200 or 300.

This would be probably sufficient, but I'd like a confirmation from
crypto people.