linux-kernel - Re: [PATCH V7 5/5] platform/x86: Intel PMT Crashlog capability driver

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Date:   Thu, 1 Oct 2020 21:46:50 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Alexander Duyck <alexander.duyck@...il.com>
Cc:     "David E. Box" <david.e.box@...ux.intel.com>,
        Lee Jones <lee.jones@...aro.org>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Alexey Budankov <alexey.budankov@...ux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        linux-pci <linux-pci@...r.kernel.org>
Subject: Re: [PATCH V7 5/5] platform/x86: Intel PMT Crashlog capability driver

On Thu, Oct 1, 2020 at 9:33 PM Alexander Duyck
<alexander.duyck@...il.com> wrote:
> On Thu, Oct 1, 2020 at 9:37 AM Andy Shevchenko
> <andy.shevchenko@...il.com> wrote:
> > On Thu, Oct 1, 2020 at 4:43 AM David E. Box <david.e.box@...ux.intel.com> wrote:

...

> Arguably not much. I'll drop the comment.
>
> > > +       control &= ~(CRASHLOG_FLAG_MASK | CRASHLOG_FLAG_DISABLE);
> >
> > How does the second constant play any role here?
>
> The "control" flags are bits 28-31, while the disable flag is bit 27
> if I recall.

Okay, then it adds more confusion to the same comment here and there.
Good you are about to drop the comment.

> Specifically bit 31 is read only, bit 28 will clear bit 31, bit 29
> will cause the crashlog to be generated and set bit 31, and bit 30 is
> just reserved 0.

Can this be added as a comment somewhere in the code?

...

> > > +       ret = intel_pmt_dev_create(entry, &pmt_crashlog_ns, parent);
> > > +       if (!ret)
> > > +               return 0;

(2)

> > > +
> > > +       dev_err(parent, "Failed to add crashlog controls\n");
> > > +       intel_pmt_dev_destroy(entry, &pmt_crashlog_ns);
> > > +
> > > +       return ret;
> >
> > Can we use traditional patterns?
> > if (ret) {
> >   ...
> > }
> > return ret;
>
> I can switch it if that is preferred.

Yes, please. The (2) is really hard to parse (easy to miss ! part and
be confused by return 0 one).

...

> > Are you going to duplicate this in each driver? Consider to refactor
> > to avoid duplication of a lot of code.
>
> So the issue lies in the complexity of pmt_telem_add_entry versus
> pmt_crashlog_add_entry. Specifically I end up needing disc_res and the
> discovery table when I go to create the controls for the crashlog
> device. Similarly we have a third device that we plan to add called a
> watcher which will require us to keep things split up like this so we
> thought it best to split it up this way.

Could you revisit and think how this can be deduplicated. I see at
least one variant with a hooks (callbacks) which you supply depending
on the driver, but the for-loop is kept in one place.

...

> > > +               .name   = DRV_NAME,
> >
> > > +MODULE_ALIAS("platform:" DRV_NAME);
> >
> > I'm not sure I have interpreted this:
> >         - Use 'raw' string instead of defines for device names
> > correctly. Can you elaborate?
>
> Again I am not sure what this is in reference to. If you can point me
> to some documentation somewhere I can take a look.

Reference to your own changelog of this series!

-- 
With Best Regards,
Andy Shevchenko