[PATCH v2 06/11] crypto: Documentation - documentation of crypto_alg

Stephan Mueller
2014-11-02T20:46:05Z

The data structure of struct crypto_alg is documented for all parameters
that can be set by a developer of a transformation. All parameters that
are internal to the crypto API are marked as such.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
CC: Marek Vasut <marex@denx.de>
---
include/linux/crypto.h | 157 ++++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 137 insertions(+), 20 deletions(-)

diff --git a/include/linux/crypto.h b/include/linux/crypto.h
index d45e949..e1a84fd 100644
--- a/include/linux/crypto.h
+++ b/include/linux/crypto.h
@@ -277,22 +277,104 @@ struct rng_alg {
#define cra_compress cra_u.compress
#define cra_rng cra_u.rng

+/**
+ * The struct crypto_alg describes a generic Crypto API algorithm and is common
+ * for all of the transformations. The flags marked as internal shall not
+ * be set or modified by a transformation implementation.
+ */
struct crypto_alg {
- struct list_head cra_list;
- struct list_head cra_users;
-
- u32 cra_flags;
- unsigned int cra_blocksize;
+ struct list_head cra_list; /** <Internal to the Crypto API */
+ struct list_head cra_users; /** <Internal to the Crypto API */
+
+ u32 cra_flags; /** <Flags describing this transformation. See
+ * include/linux/crypto.h CRYPTO_ALG_* flags for the
+ * flags which go in here. Those are used for
+ * fine-tuning the description of the transformation
+ * algorithm.
+ */
+ unsigned int cra_blocksize; /** <Minimum block size of this
+ * transformation. The size in bytes of the
+ * smallest possible unit which
+ * can be transformed with this algorithm.
+ * The users must respect this value.
+ * In case of HASH transformation, it is
+ * possible for a smaller block than
+ * .cra_blocksize to be passed to the
+ * crypto API for transformation, in case
+ * of any other transformation type, an
+ * error will be returned upon any attempt
+ * to transform smaller than .cra_blocksize
+ * chunks.
+ */
unsigned int cra_ctxsize;
- unsigned int cra_alignmask;
-
- int cra_priority;
- atomic_t cra_refcnt;
-
- char cra_name[CRYPTO_MAX_ALG_NAME];
- char cra_driver_name[CRYPTO_MAX_ALG_NAME];
-
- const struct crypto_type *cra_type;
+ unsigned int cra_alignmask; /** <Alignment mask for the input and
+ * output data buffer. The data buffer
+ * containing the input data for the
+ * algorithm must be aligned to this
+ * alignment mask. The data buffer for the
+ * output data must be aligned to this
+ * alignment mask. Note that the Crypto API
+ * will do the re-alignment in software, but
+ * only under special conditions and there
+ * is a performance hit. The re-alignment
+ * happens at these occasions for different
+ * .cra_u types:
+ * cipher: For both input data and output
+ * data buffer
+ * ahash: For output hash destination buf
+ * shash: For output hash destination buf
+ * This is needed on hardware which is
+ * flawed by design and cannot pick data
+ * from arbitrary addresses.
+ */
+
+ int cra_priority; /** <Priority of this transformation implementation.
+ * In case multiple transformations with same
+ *.cra_name are available to the Crypto API, the
+ * kernel will use the one with highest .cra_priority
+ */
+ atomic_t cra_refcnt; /** <Internal to the Crypto API */
+
+ char cra_name[CRYPTO_MAX_ALG_NAME]; /** <Generic name (usable by
+ * multiple implementations) of the
+ * transformation algorithm. This is
+ * the name of the transformation
+ * itself. This field is used by the
+ * kernel when looking up the
+ * providers of particular
+ * transformation.
+ */
+ char cra_driver_name[CRYPTO_MAX_ALG_NAME]; /** <Unique name of the
+ * transformation provider.
+ * This is the name of the
+ * provider of the
+ * transformation. This can
+ * be any arbitrary value,
+ * but in the usual case,
+ * this contains the name of
+ * the chip or provider and
+ * the name of the
+ * transformation algorithm.
+ */
+
+ const struct crypto_type *cra_type; /** <Type of the cryptographic
+ * transformation. This is a pointer
+ * to struct crypto_type, which
+ * implements callbacks common for
+ * all trasnformation types. There
+ * are multiple options:
+ * crypto_blkcipher_type
+ * crypto_ablkcipher_type
+ * crypto_ahash_type
+ * crypto_aead_type
+ * crypto_rng_type
+ * This field might be empty. In
+ * that case, there are no common
+ * callbacks. This is the case for:
+ * cipher
+ * compress
+ * shash
+ */

union {
struct ablkcipher_alg ablkcipher;
@@ -301,13 +383,48 @@ struct crypto_alg {
struct cipher_alg cipher;
struct compress_alg compress;
struct rng_alg rng;
- } cra_u;
-
- int (*cra_init)(struct crypto_tfm *tfm);
- void (*cra_exit)(struct crypto_tfm *tfm);
- void (*cra_destroy)(struct crypto_alg *alg);
+ } cra_u; /** <Callbacks implementing the transformation. This is a union
+ * of multiple structures. Depending on the type of
+ * transformation selected by .cra_type and .cra_flags above,
+ * the associated structure must be filled with callbacks.
+ * This field might be empty. This is the case for:
+ * ahash
+ * shash
+ */
+
+ int (*cra_init)(struct crypto_tfm *tfm); /** <Initialize the
+ * cryptographic transformation
+ * object. This function is
+ * used to initialize the
+ * cryptographic transformation
+ * object. This function is
+ * called only once at the
+ * instantiation time, right
+ * after the transformation
+ * context was allocated.
+ * In case the cryptographic
+ * hardware has some special
+ * requirements which need to
+ * be handled by software, this
+ * function shall check for the
+ * precise requirement of the
+ * transformation and put any
+ * software fallbacks in place.
+ */
+ void (*cra_exit)(struct crypto_tfm *tfm); /** <Deinitialize the
+ * cryptographic
+ * transformation object.
+ * This is a counterpart to
+ * .cra_init(), used to remove
+ * various changes set in
+ * .cra_init().
+ */
+ void (*cra_destroy)(struct crypto_alg *alg); /** <Internal to the Crypto
+ * API */

- struct module *cra_module;
+ struct module *cra_module; /** <Owner of this transformation
+ * implementation. Set to THIS_MODULE
+ */
};

/*
--
2.1.0