On 03/11/2017 13:06, PrasannaKumar Muralidharan wrote:
Hi Jim,
On 3 November 2017 at 15:27, Jim Quigley <Jim.Quigley@xxxxxxxxxx> wrote:
The patch for
commit: 5c06273401f2eb7b290cadbae18ee00f8f65e893
Author: Amit Shah <amit.shah@xxxxxxxxxx>
Date: Sun Jul 27 07:34:01 2014 +0930
virtio: rng: delay hwrng_register() till driver is ready
moved the call to hwrng_register() out of the probe routine into the scan
routine. We need to call hwrng_register() after a suspend/restore cycle
to re-register the device, but the scan function is not invoked for the
restore. Add the call to hwrng_register() to virtio_restore().
Reviewed-by: Liam Merwick <Liam.Merwick@xxxxxxxxxx>
Signed-off-by: Jim Quigley <Jim.Quigley@xxxxxxxxxx>
---
drivers/char/hw_random/virtio-rng.c | 21 ++++++++++++++++++++-
1 file changed, 20 insertions(+), 1 deletion(-)
diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c
index 3fa2f8a..b89df66 100644
--- a/drivers/char/hw_random/virtio-rng.c
+++ b/drivers/char/hw_random/virtio-rng.c
@@ -184,7 +184,26 @@ static int virtrng_freeze(struct virtio_device *vdev)
static int virtrng_restore(struct virtio_device *vdev)
{
- return probe_common(vdev);
+ int err;
+
+ err = probe_common(vdev);
+ if (!err) {
+ struct virtrng_info *vi = vdev->priv;
+
+ /*
+ * Set hwrng_removed to ensure that virtio_read()
+ * does not block waiting for data before the
+ * registration is complete.
+ */
+ vi->hwrng_removed = true;
+ err = hwrng_register(&vi->hwrng);
+ if (!err) {
+ vi->hwrng_register_done = true;
+ vi->hwrng_removed = false;
+ }
+ }
+
+ return err;
}
#endif
--
1.8.3.1
This patch makes me wonder why hwrng_unregister is required in
virtrng_freeze. Looks strange and unusual. May be that is not required
and it can be removed. If it is required can you please add a comment
on why it is required?
The reason it's required is because the virtrng_restore() uses
probe_common() which allocates
a new virtrng_info struct, changing the devices private pointer .
This virtrng struct is used in
hwrng_register() to set the current RNG etc. If we don't
unregister/re-register then we would
need to split probe_common() to avoid
vi = kzalloc(sizeof(struct virtrng_info), GFP_KERNEL);
overwriting vdev->priv on a restore.
It would be cleaner to just get rid of probe_common() altogether in
that case, and do whatever
needs to be done in virtrng_probe()/virtrng_restore() respectively,
but I didn't want to change code
affecting the normal probe path as well as suspend/resume. Is it OK
to leave it that way to avoid
the more extensive changes ?
thanks
regards
Jim Q.
Thanks,
PrasannaKumar
