Re: [virtio-dev] Re: [PATCH v2 2/9] ALSA: virtio: add virtio sound driver

Hi Takashi,


On 03.02.2021 17:59, Takashi Iwai wrote:

On Tue, 02 Feb 2021 00:18:09 +0100,
Anton Yakovlev wrote:

quoted

quoted

quoted

+/**
+ * virtsnd_reset_fn() - Kernel worker's function to reset the device.
+ * @work: Reset device work.
+ *
+ * Context: Process context.
+ */
+static void virtsnd_reset_fn(struct work_struct *work)
+{
+     struct virtio_snd *snd =
+             container_of(work, struct virtio_snd, reset_work);
+     struct virtio_device *vdev = snd->vdev;
+     struct device *dev = &vdev->dev;
+     int rc;
+
+     dev_info(dev, "sound device needs reset\n");
+
+     /*
+      * It seems that the only way to properly reset the device is to
remove
+      * and re-create the ALSA sound card device.
+      *
+      * Also resetting the device involves a number of steps with
setting the
+      * status bits described in the virtio specification. And the
easiest
+      * way to get everything right is to use the virtio bus interface.
+      */
+     rc = dev->bus->remove(dev);
+     if (rc)
+             dev_warn(dev, "bus->remove() failed: %d", rc);
+
+     rc = dev->bus->probe(dev);
+     if (rc)
+             dev_err(dev, "bus->probe() failed: %d", rc);

This looks very suspicious to me. Wondering what ALSA maintainers

will say

quoted

to this.

I'm also wondering what the virtio people have to say. This part is a
purely virtio specific thing. And since none of the existing virtio
drivers processes the request to reset the device, it is not clear what
is the best way to proceed here. For this reason, the most
straightforward and simple solution was chosen.

What is this "reset" actually supposed to do?  Reconfguring
everything, or changing only certain parameters, devices, whatever?

It means bringing this particular device to its initial state.

After that, the driver can re-read the configurations from the device
and reconfigure everything.

thanks,

Takashi

-- 
Anton Yakovlev
Senior Software Engineer

OpenSynergy GmbH
Rotherstr. 20, 10245 Berlin

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