netdev - Re: [net-next v4 10/12] ASoC: SOF: Introduce descriptors for SOF client

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Date:   Mon, 29 Jun 2020 21:59:10 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Cc:     Jason Gunthorpe <jgg@...pe.ca>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        davem@...emloft.net, gregkh@...uxfoundation.org,
        netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
        nhorman@...hat.com, sassmann@...hat.com,
        Fred Oh <fred.oh@...ux.intel.com>
Subject: Re: [net-next v4 10/12] ASoC: SOF: Introduce descriptors for SOF
 client

On Fri, May 22, 2020 at 10:33:20AM -0500, Pierre-Louis Bossart wrote:
> On 5/22/20 9:55 AM, Jason Gunthorpe wrote:

> > Maybe not great, but at least it is consistent with all the lifetime
> > models and the operation of the driver core.

> I agree your comments are valid ones, I just don't have a solution to be
> fully compliant with these models and report failures of the driver probe
> for a child device due to configuration issues (bad audio topology, etc).

> My understanding is that errors on probe are explicitly not handled in the
> driver core, see e.g. comments such as:

It's just not an error for a child device to not instantiate, we don't
even know if the driver is loaded yet.  The parent really should not
care if the child is there or not.

> > > PCI device creates an audio card represented as a platform device. When the
> > > card registration fails, typically due to configuration issues, the PCI
> > > probe still completes. That's really confusing and the source of lots of
> > > support questions. If we use these virtual bus extensions to stpo abusing
> > > platform devices, it'd be really nice to make those unreported probe
> > > failures go away.

> > I think you need to address this in some other way that is hot plug
> > safe.

> > Surely you can make this failure visible to users in some other way?

> Not at the moment, no. there are no failures reported in dmesg, and the user
> does not see any card created. This is a silent error.

If we're failing to do something we should report it.  This includes
deferred probe failures.

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