2010-12-14 16:08:45

by Mark Allyn

Subject: Questions on ahash

Folks:

I am having trouble figuring out the structures used for ahash.

First of all, I see very little commenting on the various structure
elements.

Here is my attempt to expand out the ahash_alg structre (with my
questions interspaced . . .

This is the top level structure

struct ahash_alg {
int (*init)(struct ahash_request *req);

***Question; What is this init for?

int (*update)(struct ahash_request *req);
int (*final)(struct ahash_request *req);
int (*finup)(struct ahash_request *req);
int (*digest)(struct ahash_request *req);
int (*export)(struct ahash_request *req, void *out);
int (*import)(struct ahash_request *req, const void *in);
int (*setkey)(struct crypto_ahash *tfm, const u8 *key,
unsigned int keylen);

Question: If all I do for initializing my device is to set the key,
then do I even need the other three init function pointers in this
structure?

struct hash_alg_common halg;

which is this structure
=========================================
struct hash_alg_common {
unsigned int digestsize;
unsigned int statesize;

struct crypto_alg base;

#########################################3
Which in turn is this structure
struct crypto_alg {
struct list_head cra_list;
struct list_head cra_users;

u32 cra_flags;

Question: What are these flags?

unsigned int cra_blocksize;
unsigned int cra_ctxsize;
unsigned int cra_alignmask;

Question: What is the 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;

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Which is this structure
struct crypto_type {
unsigned int (*ctxsize)(struct crypto_alg *alg, u32 type, u32
mask);
unsigned int (*extsize)(struct crypto_alg *alg);

Questions: What are these for? Is ctxsize merely the size of the
context structure that my device needs? What is extsize?

int (*init)(struct crypto_tfm *tfm, u32 type, u32 mask);
int (*init_tfm)(struct crypto_tfm *tfm);

Question; What is this init for? You have another one above. . .

void (*show)(struct seq_file *m, struct crypto_alg *alg);
struct crypto_alg *(*lookup)(const char *name, u32 type, u32
mask);

unsigned int type;
unsigned int maskclear;
unsigned int maskset;

Question: What are type, maskclear, and maskset?

unsigned int tfmsize;
};
End of crypto_type structure (*cry_type)
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

union {
struct ablkcipher_alg ablkcipher;
struct aead_alg aead;
struct blkcipher_alg blkcipher;
struct cipher_alg cipher;
struct compress_alg compress;
struct rng_alg rng;
} cra_u;

int (*cra_init)(struct crypto_tfm *tfm);

Question: What is this init for? There are two others. Do I merely use my
device's init function (which sets the key) for all three of these inits?

void (*cra_exit)(struct crypto_tfm *tfm);
void (*cra_destroy)(struct crypto_alg *alg);

struct module *cra_module;

Question: What is this module? Is this the same as the one defined in
include/linux/module.h?

};
end of crypto_alg (base)
###############################################33

end of struct hash_alg_common (halg)
=========================================

};

Thank you for your help

Truly,

Mark Allyn
Portland, Oregon
http://www.allyn.com
971-563-7588