[PATCH] crypto: doc - clarify hash callbacks state machine

["Horia Geantă" <horia.geanta@nxp.com>]

Even though it doesn't make too much sense, it is perfectly legal to:
- call .init() and then (as many times) .update()
- subseqently _not_ call any of .final(), .finup() or .export()

Update documentation since this is an important issue to consider
from resource management perspective.

Link: https://lkml.kernel.org/r/20180222114741.GA27631@gondor.apana.org.au
Signed-off-by: Horia Geantă <horia.geanta@nxp.com>
---
 Documentation/crypto/devel-algos.rst | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/Documentation/crypto/devel-algos.rst b/Documentation/crypto/devel-algos.rst
index 66f50d32dcec..0f4617019227 100644
--- a/Documentation/crypto/devel-algos.rst
+++ b/Documentation/crypto/devel-algos.rst
@@ -236,6 +236,14 @@ when used from another part of the kernel.
                                |
                                '---------------> HASH2
 
+Note that it is perfectly legal to:
+- call .init() and then (as many times) .update()
+- subseqently _not_ call any of .final(), .finup() or .export()
+
+In other words mind the resource allocation and clean-up,
+since this basically means no resources can remain allocated
+after a call to .init() or .update().
+
 
 Specifics Of Asynchronous HASH Transformation
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- 
2.16.2

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