I do not understand DigestSignInit

[Steffen Nurpmeso]

Steffen Nurpmeso wrote in
 <20240203024616.Vqb451KI at steffen%sdaoden.eu>:
 |Has anyone knowledge on how i can automatically determine whether
 |i need to call
 |
 |  EVP_DigestSignInit(mdcp, NIL, mdp, NIL, pkeyp)
 |
 |or
 |
 |  EVP_DigestSignInit(mdcp, NIL, NIL, NIL, pkeyp)
 |
 |That is, a way to determine whether a EVP_PKEY is "configurable
 |regarding the used message-digest", or whether it has a built-in
 |approach of digest-signing?

And also, while i am here, is there any PKEY interface that tells
me whether the PKEY supports stream-based aka iterative
Update/Final?  Just in case there is a key type which allows
"configurable message-digest" but still requires one-shot because
it iterates over the data multiple times, or so.

Thank you!!

--steffen
|
|Der Kragenbaer,                The moon bear,
|der holt sich munter           he cheerfully and one by one
|einen nach dem anderen runter  wa.ks himself off
|(By Robert Gernhardt)