linux-kernel - Re: [PATCH v8 2/4] drivers/acpi: Introduce Platform Firmware Runtime Update device driver

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Message-ID: <20211108120800.GA619906@chenyu-desktop>
Date:   Mon, 8 Nov 2021 20:08:00 +0800
From:   Chen Yu <yu.c.chen@...el.com>
To:     Andy Shevchenko <andriy.shevchenko@...el.com>
Cc:     linux-acpi@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Ard Biesheuvel <ardb@...nel.org>, Len Brown <lenb@...nel.org>,
        Ashok Raj <ashok.raj@...el.com>,
        Mike Rapoport <rppt@...nel.org>,
        Aubrey Li <aubrey.li@...el.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 2/4] drivers/acpi: Introduce Platform Firmware Runtime
 Update device driver

On Mon, Nov 08, 2021 at 11:20:22AM +0200, Andy Shevchenko wrote:
> On Sat, Nov 06, 2021 at 11:14:56PM +0800, Chen Yu wrote:
> > On Wed, Nov 03, 2021 at 07:32:09PM +0200, Andy Shevchenko wrote:
> > > On Wed, Nov 03, 2021 at 11:43:50PM +0800, Chen Yu wrote:
> 
> ...
> 
> > > > +enum cap_index {
> > > > +	CAP_STATUS_IDX = 0,
> > > > +	CAP_UPDATE_IDX = 1,
> > > > +	CAP_CODE_TYPE_IDX = 2,
> > > > +	CAP_FW_VER_IDX = 3,
> > > > +	CAP_CODE_RT_VER_IDX = 4,
> > > > +	CAP_DRV_TYPE_IDX = 5,
> > > > +	CAP_DRV_RT_VER_IDX = 6,
> > > > +	CAP_DRV_SVN_IDX = 7,
> > > > +	CAP_PLAT_ID_IDX = 8,
> > > > +	CAP_OEM_ID_IDX = 9,
> > > > +	CAP_OEM_INFO_IDX = 10,
> > > 
> > > > +	CAP_NR_IDX = 11
> > > 
> > > Assignment here doesn't make any sense (it just adds unneeded churn and
> > > burden). Same to the rest of similar cases below.
> > >
> > Greg mentioned that, we might need to "explicit about the numbers here, because it
> > is uncerntain this is guaranteed by all C compilers or not."
> > https://lore.kernel.org/lkml/YXj+QaMcCeV71XbI@kroah.com/
> > My understanding is that, this applys to both uapi headers and the kernel internal
> > headers.
> 
> I was talking only about the last item. This is guaranteed to be LAST+1 by the
> C standard and any deviation from that is a compiler bug that must be fixed.
> 
> The first elements may be explicitly defined so we will be sure they are always
> stay. Greg is right about it.
>
Ok, got it. Previously I've sent a v9 patch set that addressed the issues in v8, except
for this enum issue. I'll wait for a day or two, if there is no further comments on
v9, I'll send a refreshed v10 with this enum issue fixed.

thanks,
Chenyu