linux-kernel - Re: [PATCH V12 4/9] cxl/pci: Create PCI DOE mailbox's for memory devices

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Message-ID: <Yr9Qiv/tV8f9z+Xx@iweiny-desk3>
Date:   Fri, 1 Jul 2022 12:52:42 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     Davidlohr Bueso <dave@...olabs.net>
CC:     Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lukas Wunner <lukas@...ner.de>,
        Alison Schofield <alison.schofield@...el.com>,
        "Vishal Verma" <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        "Ben Widawsky" <bwidawsk@...nel.org>,
        <linux-kernel@...r.kernel.org>, <linux-cxl@...r.kernel.org>,
        <linux-pci@...r.kernel.org>
Subject: Re: [PATCH V12 4/9] cxl/pci: Create PCI DOE mailbox's for memory
 devices

On Thu, Jun 30, 2022 at 09:14:06AM -0700, Davidlohr Bueso wrote:
> On Thu, 30 Jun 2022, Jonathan Cameron wrote:
> 
> > On Wed, 29 Jun 2022 22:32:57 -0700 Ira Weiny <ira.weiny@...el.com> wrote:
> 
> > > I _thought_ that we did not care if some mailboxes failed or not.
> > 
> > I have a different view to Dan on this.  In my view if your hardware is
> > not working in any way at all scream like mad don't carry on... Dan
> > is keen to try to muddle onwards.
> 
> I am also of the idea of not carrying on upon any indication of failure.
> 
> > > 
> > > If CDAT is not supported on any of the mailboxes found then CDAT will not show
> > > up on sysfs (as per Dan's last comment).  If it was supported on a mailbox but
> > > no data is found the sysfs will show up but be 0 length.
> > > 
> > > At this layer I thought we agreed to skip over these errors.  If a protocol is
> > > needed at a higher layer and it is not found on any of the mailboxes the errors
> > > should show up in that layer.  In this series CDAT is not 100% necessary as
> > > devices can work without it.  So the errors were mostly paper'ed over in favor
> > > of just printing error messages and muddle on.
> > > 
> > > The xa_insert() deserves a pci_err() though.
> > 
> > That's probably the minimum we should do.  The xa_insert() failing is something
> > horrible going wrong in our software / host afterall.
> 
> Yes. And in addition, devm_cxl_pci_create_doe() should return any error status, and
> cxl_pci_probe() can choose to omit any errors, but it's still better to have it.

I don't think this adds anything.  If devm_cxl_pci_create_doe() already prints
error messages what is cxl_pci_probe() going to do with the error if it does
not fail the probe?

I want devm_cxl_pci_create_doe() to continue trying to create the mailbox
objects.  So for now I'm going to print the errors in devm_cxl_pci_create_doe()
and keep going without returning any error.

Ira

> 
> Thanks,
> Davidlohr