[drm] *ERROR* mstb 0000000057b5b857 port 1: DPCD read on addr 0x4b0 for 1 bytes NAKed

[Lyude Paul]

On Thu, 2022-02-17 at 23:07 +0100, Jocelyn Falempe wrote:
> On 17/02/2022 19:15, Lyude Paul wrote:
> > Hi! Sorry for the late reply, I had to take some time off work
> > unexpectedly.
> > This is normal (although not great TBH, I'm not sure we should be printing
> > an
> > error message for that), it's the result of fwupd trying to probe the MST
> > hub
> > to see if it's a specific Dell dock that can receive updates over DP aux,
> > but
> > it's not smart enough to know it doesn't need to poke the DP aux ranges of
> > downstream branches or non-MST ports in general.
> I think MST topology is not exposed to userspace, so it would be hard 
> for fwupd to be smarter than that.

We actually do expose a connector prop called "path" (or something like that)
that can be used to determine this. although the format for that is admittedly
a bit strange, but it should work

> 
> > 
> > Would definitely accept patches to make this a non-error, or at least make
> > this a non-error when the read/writes come from userspace
> 
> I will try to provide a patch for this.
> 
> Thanks,
> 

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat