Understanding HASH(SHA) Driver implementation

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Hi ,

I am trying to analyze Linux Kernel Crypto Interface with respective
to hashing(ahash for SHA1 in particular) . I am looking at
omap-sham.c/atmel-sha.c as reference,which is in open source
linux/driver/crypto.I need some inputs in understanding following .

#1: If It need to handle a scenario where in which multiple messages
will be given to generate a digest/Hash message like below.

Ex:  Input Block =  buffer1 + buffer2 +.... +buffern

if I need to generate hash for Input Block(could be anything like a
fwimage/file etc) , Then I ll split it into some buffers and I ll send
it
in chunks like buffer1,bffer2 etc to underlying crypto driver


Hash( Input Block) = Hash(buffer1) + Hash(buffer2) + ..... + Hash( buffern)
                                   |                       |
    + ..... +    |
                                   |                       |
                   |
                               sha_update(*)      sha_update(*)
 sha_update(*)


How is it possible to keep track/store intermediate Hash generated data
like for buffer1,buffer2 etc ?

#2: what is the need to have multiple structures like  "*_sha_reqctx "
and "*_sha_dev" ?

As Per my understanding "*_sha_reqctx" structure  is for generic Linux
Kernel Crypto crypto context to interact with specific crypto request
and
"*_sha_dev" structure is for Hardware specific some thing like for any
DMA related operations.

BR,
Srisowj
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