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Subject[RFC PATCH] crypto: make the seed() function optional
Date
This makes it simplier for driver author to not provide the seed() function
in case of a pseudo RNG where the seed operation is a no-op.

Document that the seed() function pointer is optional in header.

Signed-off-by: Mathieu Malaterre <malat@debian.org>
---
The PRNG as found on Ingenic JZ4780 is one such example. This is found on a
MIPS Creator CI20 SoC.

crypto/rng.c | 7 ++++++-
include/crypto/rng.h | 2 +-
2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/crypto/rng.c b/crypto/rng.c
index 5e8469244960..ed08581901a9 100644
--- a/crypto/rng.c
+++ b/crypto/rng.c
@@ -35,9 +35,14 @@ static int crypto_default_rng_refcnt;

int crypto_rng_reset(struct crypto_rng *tfm, const u8 *seed, unsigned int slen)
{
+ struct rng_alg *ralg = crypto_rng_alg(tfm);
u8 *buf = NULL;
int err;

+ /* In case of PRNG, no need to seed */
+ if (!ralg->seed)
+ return 0;
+
if (!seed && slen) {
buf = kmalloc(slen, GFP_KERNEL);
if (!buf)
@@ -47,7 +52,7 @@ int crypto_rng_reset(struct crypto_rng *tfm, const u8 *seed, unsigned int slen)
seed = buf;
}

- err = crypto_rng_alg(tfm)->seed(tfm, seed, slen);
+ err = ralg->seed(tfm, seed, slen);

kzfree(buf);
return err;
diff --git a/include/crypto/rng.h b/include/crypto/rng.h
index b95ede354a66..ac5d061d0297 100644
--- a/include/crypto/rng.h
+++ b/include/crypto/rng.h
@@ -32,7 +32,7 @@ struct crypto_rng;
* random number generator requires a seed for setting
* up a new state, the seed must be provided by the
* consumer while invoking this function. The required
- * size of the seed is defined with @seedsize .
+ * size of the seed is defined with @seedsize. Optional.
* @set_ent: Set entropy that would otherwise be obtained from
* entropy source. Internal use only.
* @seedsize: The seed size required for a random number generator
--
2.11.0
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