Messages in this thread | | | Date | Tue, 20 Jan 2015 13:09:55 +0200 | From | "Michael S. Tsirkin" <> | Subject | Re: [PATCH v3 04/16] virtio/console: verify device has config space |
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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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