Hi Herbert,
On Tue, Feb 16, 2016 at 07:57:17PM +0000, Herbert Xu wrote:
> Can you give an example on how to use the noctx support with
> your acomp interface?
In this version of the acomp api an algorithm can specify different sizes for
the compression and the decompression contexts by setting the comp_reqsize and
the decomp_reqsize fields in the acomp_alg structure.
The api also provides two new function calls to allocate the request:
struct acomp_req *acomp_compression_request_alloc(
struct crypto_acomp *acomp, gfp_t gfp)
struct acomp_req *acomp_decompression_request_alloc(
struct crypto_acomp *acomp, gfp_t gfp)
The implementation of these calls use comp_reqsize and decomp_reqsize to
allocate the context and therefore, if an algorithm supports it, it is possible
to have requests with no context.
Here is a simple example that shows how to use the api from a user prospective:
struct crypto_acomp *tfm;
struct acomp_req *req = NULL;
struct scatterlist src;
struct scatterlist dst;
tfm = crypto_alloc_acomp("deflate", 0, 0);
req = acomp_compression_request_alloc(tfm, GFP_KERNEL);
/* Prepare src and dst sgls */
acomp_request_set_params(req, &src, &dst, slen, dlen);
acomp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG, cb_func,
cb_data);
ret = crypto_acomp_compress(req);
Regarding the SCOMP backends, when an algorithm registers as
CRYPTO_ALG_TYPE_SCOMPRESS, requests allocated with both
acomp_compression_request_alloc and acomp_decompression_request_alloc have
the same size (sizeof (struct acomp_req) + sizeof(void *)).
The request context stores a pointer to the scomp context allocated
using crypto_scomp_alloc_ctx().
If the algorithm specifies the CRYPTO_SCOMP_DECOMP_NOCTX flag,
acomp_decompression_request_alloc does not call crypto_scomp_alloc_ctx() and
stores NULL into the request context.
This way the scomp context is not allocated and decompression requests are
called without context. See patch v3.
Regards,
--
Giovanni
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