On Tue, Jan 20, 2015 at 04:10:40PM +0530, Amit Shah wrote:
> On (Wed) 14 Jan 2015 [19:27:35], Michael S. Tsirkin wrote:
> > Some devices might not implement config space access
> > (e.g. remoteproc used not to - before 3.9).
> > virtio/console needs config space access so make it
> > fail gracefully if not there.
>
> Do we know any such devices? Wondering what prompted this patch. If
> it's just theoretical, I'd rather let it be like this, and pull this
> in when there's a device that doesn't have config space.
Yes, with virtio 1.0 config space can be in a separate BAR now. If
that's not enabled by BIOS (e.g. out of space), we won't have config
space.
> Also, just the console functionality (i.e. F_MULTIPORT is unset) is
> available w/o config space access.
Supporting this by gracefully disabling F_MULTIPORT
would require getting this info from driver before
features are finalized.
Alternatively, check F_MULTIPORT and only fail if set?
Let me know, I'll cook up a patch.
> In fact, getting this patch in
> would mean remoteproc wouldn't even run in its pre-config days...
It seems to have get callback unconditionally now - or did I miss
something?
> > diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> > index de03df9..26afb56 100644
> > --- a/drivers/char/virtio_console.c
> > +++ b/drivers/char/virtio_console.c
> > @@ -1986,6 +1986,12 @@ static int virtcons_probe(struct virtio_device *vdev)
> > bool multiport;
> > bool early = early_put_chars != NULL;
> >
> > + if (!vdev->config->get) {
> > + dev_err(&vdev->dev, "%s failure: config access disabled\n",
> > + __func__);
> > + return -EINVAL;
> > + }
> > +
>
>
> Amit
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