Hardware random number generators are supposed to use the hw_random
framework. This commit turns ath9k's kthread-based design into a proper
hw_random driver.

This compiles, but I have no hardware or other ability to determine
whether it works. I'll leave further development up to the ath9k
and hw_random maintainers.

Cc: Toke Høiland-Jørgensen <redacted>
Cc: Kalle Valo <kvalo@kernel.org>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 drivers/net/wireless/ath/ath9k/ath9k.h |  2 +-
 drivers/net/wireless/ath/ath9k/rng.c   | 62 +++++++++-----------------
 2 files changed, 23 insertions(+), 41 deletions(-)

diff --git a/drivers/net/wireless/ath/ath9k/ath9k.h b/drivers/net/wireless/ath/ath9k/ath9k.h
index ef6f5ea06c1f..142f472903dc 100644
--- a/drivers/net/wireless/ath/ath9k/ath9k.h
+++ b/drivers/net/wireless/ath/ath9k/ath9k.h

@@ -1072,7 +1072,7 @@ struct ath_softc {
 
 #ifdef CONFIG_ATH9K_HWRNG
 	u32 rng_last;
-	struct task_struct *rng_task;
+	struct hwrng rng_ops;
 #endif
 };
 

diff --git a/drivers/net/wireless/ath/ath9k/rng.c b/drivers/net/wireless/ath/ath9k/rng.c
index aae2bd3cac69..369b222908ba 100644
--- a/drivers/net/wireless/ath/ath9k/rng.c
+++ b/drivers/net/wireless/ath/ath9k/rng.c

@@ -22,9 +22,6 @@
 #include "hw.h"
 #include "ar9003_phy.h"
 
-#define ATH9K_RNG_BUF_SIZE	320
-#define ATH9K_RNG_ENTROPY(x)	(((x) * 8 * 10) >> 5) /* quality: 10/32 */

@@ -72,61 +69,46 @@ static u32 ath9k_rng_delay_get(u32 fail_stats)
 	return delay;
 }
 
-static int ath9k_rng_kthread(void *data)
+static int ath9k_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
 {
+	struct ath_softc *sc = container_of(rng, struct ath_softc, rng_ops);
 	int bytes_read;
-	struct ath_softc *sc = data;
-	u32 *rng_buf;
-	u32 delay, fail_stats = 0;
-
-	rng_buf = kmalloc_array(ATH9K_RNG_BUF_SIZE, sizeof(u32), GFP_KERNEL);
-	if (!rng_buf)
-		goto out;
-
-	while (!kthread_should_stop()) {
-		bytes_read = ath9k_rng_data_read(sc, rng_buf,
-						 ATH9K_RNG_BUF_SIZE);
-		if (unlikely(!bytes_read)) {
-			delay = ath9k_rng_delay_get(++fail_stats);
-			wait_event_interruptible_timeout(rng_queue,
-							 kthread_should_stop(),
-							 msecs_to_jiffies(delay));
-			continue;
-		}
-
-		fail_stats = 0;
-
-		/* sleep until entropy bits under write_wakeup_threshold */
-		add_hwgenerator_randomness((void *)rng_buf, bytes_read,
-					   ATH9K_RNG_ENTROPY(bytes_read));
-	}
+	u32 fail_stats = 0;
 
-	kfree(rng_buf);
-out:
-	sc->rng_task = NULL;
+retry:
+	bytes_read = ath9k_rng_data_read(sc, buf, max);