crypto: doc - adapt api sample to use async. op wait

The code sample is waiting for an async. crypto op completion.
Adapt sample to use the new generic infrastructure to do the same.

This also fixes a possible data coruption bug created by the
use of wait_for_completion_interruptible() without dealing
correctly with an interrupt aborting the wait prior to the
async op finishing.
Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Documentation/crypto/api-samples.rst

@@ -7,59 +7,27 @@ Code Example For Symmetric Key Cipher Operation
 ::
 
 
-    struct tcrypt_result {
-        struct completion completion;
-        int err;
-    };
-
     /* tie all data structures together */
     struct skcipher_def {
         struct scatterlist sg;
         struct crypto_skcipher *tfm;
         struct skcipher_request *req;
-        struct tcrypt_result result;
+        struct crypto_wait wait;
     };
 
-    /* Callback function */
-    static void test_skcipher_cb(struct crypto_async_request *req, int error)
-    {
-        struct tcrypt_result *result = req->data;
-
-        if (error == -EINPROGRESS)
-            return;
-        result->err = error;
-        complete(&result->completion);
-        pr_info("Encryption finished successfully\n");
-    }
-
     /* Perform cipher operation */
     static unsigned int test_skcipher_encdec(struct skcipher_def *sk,
                          int enc)
     {
-        int rc = 0;
+        int rc;
 
         if (enc)
-            rc = crypto_skcipher_encrypt(sk->req);
+            rc = crypto_wait_req(crypto_skcipher_encrypt(sk->req), &sk->wait);
         else
-            rc = crypto_skcipher_decrypt(sk->req);
-
-        switch (rc) {
-        case 0:
-            break;
-        case -EINPROGRESS:
-        case -EBUSY:
-            rc = wait_for_completion_interruptible(
-                &sk->result.completion);
-            if (!rc && !sk->result.err) {
-                reinit_completion(&sk->result.completion);
-                break;
-            }
-        default:
-            pr_info("skcipher encrypt returned with %d result %d\n",
-                rc, sk->result.err);
-            break;
-        }
-        init_completion(&sk->result.completion);
+            rc = crypto_wait_req(crypto_skcipher_decrypt(sk->req), &sk->wait);
+
+	if (rc)
+		pr_info("skcipher encrypt returned with result %d\n", rc);
 
         return rc;
     }
@@ -89,8 +57,8 @@ Code Example For Symmetric Key Cipher Operation
         }
 
         skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
-                          test_skcipher_cb,
-                          &sk.result);
+                          crypto_req_done,
+                          &sk.wait);
 
         /* AES 256 with random key */
         get_random_bytes(&key, 32);
@@ -122,7 +90,7 @@ Code Example For Symmetric Key Cipher Operation
         /* We encrypt one block */
         sg_init_one(&sk.sg, scratchpad, 16);
         skcipher_request_set_crypt(req, &sk.sg, &sk.sg, 16, ivdata);
-        init_completion(&sk.result.completion);
+        crypto_init_wait(&sk.wait);
 
         /* encrypt data */
         ret = test_skcipher_encdec(&sk, 1);