我尝试使用Linux Crypto API在内核模块中计算sha1哈希，但是我找不到有关如何设置异步请求使用的分散列表的信息。另外，我应该如何等待异步操作完成？

static int plaintext_to_sha1(void) {

struct scatterlist sg[8];

struct crypto_ahash *tfm;

struct ahash_request *req;

char *plaintext = "TEST!\0";

unsigned char *result = kmalloc(sizeof(unsigned char) * SHA1_LENGTH, GFP_KERNEL);

unsigned int len = strlen(plaintext);

tfm = crypto_alloc_ahash("sha1", 0, CRYPTO_ALG_ASYNC);

if (IS_ERR(tfm)) {

printk(KERN_ERR "tfm allocation failed\n");

return -1;

}

/* ... set up the scatterlists ... */

req = ahash_request_alloc(tfm, GFP_ATOMIC);

if (!req) {

printk(KERN_ERR "request allocation failed\n");

return -1;

}

ahash_request_set_callback(req, 0, NULL, NULL);

ahash_request_set_crypt(req, sg, result, 2);

if (crypto_ahash_digest(req)) {

printk(KERN_ERR "digest failed\n");

return -1;

}

ahash_request_free(req);

crypto_free_ahash(tfm);

return 0;

}