TPM2_Sign vs TPM2_RSA_Decrypt

["Jarkko Sakkinen" <jarkko@kernel.org>]

Hi,

I'm pushing with James Prestwood RSA and ECDSA based asymmetric keys to
asymmetric keys subsystem of the kernel and for e.g. RSA we can just use
TPM2_RSA_Decrypt:

https://lore.kernel.org/all/20200518172704.29608-18-prestwoj@gmail.com/

I've implemented some code that make this fit more cleanly to the kernel
and James will refactor his old code on top of that. I.e. add the
padding and asn1 data and make x.509 compatible scheme. Just do
textbook style RSA part with TPM2.

Just for plain interest, because I'm not too familiar with TPM2_Sign:
when would you choose to use it instead? I just want to make sure that
we're doing right things right :-)

BR, Jarkko