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

Andy Shevchenko
2021-11-08T09:20:40Z

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.

> > > +};

--
With Best Regards,
Andy Shevchenko