linux-kernel - Re: [PATCH v3 1/5] ACPI / blacklist: add acpi_match_platform

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Date:   Mon, 21 Aug 2017 21:06:42 +0000
From:   "Kani, Toshimitsu" <toshi.kani@....com>
To:     "bp@...en8.de" <bp@...en8.de>,
        "rafael@...nel.org" <rafael@...nel.org>
CC:     "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "lenb@...nel.org" <lenb@...nel.org>,
        "mchehab@...nel.org" <mchehab@...nel.org>,
        "tony.luck@...el.com" <tony.luck@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        "rjw@...ysocki.net" <rjw@...ysocki.net>
Subject: Re: [PATCH v3 1/5] ACPI / blacklist: add acpi_match_platform_list()

On Mon, 2017-08-21 at 22:31 +0200, Rafael J. Wysocki wrote:
> On Mon, Aug 21, 2017 at 7:36 PM, Borislav Petkov <bp@...en8.de>
> wrote:
> > On Mon, Aug 21, 2017 at 05:23:37PM +0000, Kani, Toshimitsu wrote:
> > > > > 'data' here is private to the caller.  So, I do not think we
> > > > > need to define the bits.  Shall I change the name to
> > > > > 'driver_data' to make it more explicit?
> > > > 
> > > > You changed it to 'data'. It was a u32-used-as-boolean
> > > > is_critical_error before.
> > > > 
> > > > So you can just as well make it into flags and people can
> > > > extend those flags if needed. A flag bit should be enough in
> > > > most cases anyway. If they really need driver_data, then they
> > > > can add a void *member.
> > > 
> > > Hmm.. In patch 2, intel_pstate_platform_pwr_mgmt_exists() uses
> > > this field for PSS and PCC, which are enum values.  I think we
> > > should allow drivers to set any values here.  I agree that it may
> > > need to be void * if we also allow drivers to set a pointer here.
> > 
> > Let's see what Rafael prefers.
> 
> I would retain the is_critical_error field and use that for printing
> the recoverable / non-recoverable message.  This is kind of
> orthogonal to whether or not any extra data is needed and that can be
> an additional field.  In that case unsigned long should be sufficient
> to accommodate a pointer if need be.

Yes, we will retain the field.  The question is whether this field
should be retained as a driver's private data or ACPI-managed flags.  

My patch implements the former, which lets the callers to define the
data values.  For instance, acpi_blacklisted() uses this field as
is_critical_error value, and intel_pstate_platform_pwr_mgmt_exists()
uses it as oem_pwr_table value.

Boris suggested the latter, which lets ACPI to define the flags, which
are then used by the callers.  For instance, he suggested ACPI to
define bit0 as is_critical_error.

#define ACPI_PLAT_IS_CRITICAL_ERROR     BIT(0)

Thanks,
-Toshi