linux-kernel - Re: [PATCH v2] ACPI: LPSS: use acpi_dev_uid_match() for matching

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Date:   Mon, 30 Oct 2023 18:00:16 +0200
From:   Raag Jadav <raag.jadav@...el.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        len.brown@...el.com, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        mallikarjunappa.sangannavar@...el.com, bala.senthil@...el.com
Subject: Re: [PATCH v2] ACPI: LPSS: use acpi_dev_uid_match() for matching _UID

On Mon, Oct 30, 2023 at 12:12:27PM +0200, Andy Shevchenko wrote:
> On Sat, Oct 28, 2023 at 11:58:12AM +0300, Raag Jadav wrote:
> > On Fri, Oct 27, 2023 at 07:40:38PM +0200, Rafael J. Wysocki wrote:
> 
> ...
> 
> > We'd probably end up with an oops trying to strcmp into a random address
> > without knowing its type, so I think Mika's would be a better approach.
> > 
> > #define acpi_dev_uid_match(adev, uid2)                                                          \
> > ({                                                                                              \
> >         const char *uid1 = acpi_device_uid(adev);                                               \
> >         u64 __uid1;                                                                             \
> >                                                                                                 \
> >         _Generic(uid2,                                                                          \
> >                  int: uid1 && !kstrtou64(uid1, 0, &__uid1) && (typeof(uid2))__uid1 == uid2,     \
> >                  const char *: uid1 && uid2 && !strcmp(uid1, (const char *)uid2),               \
> >                  default: false);                                                               \
> >                                                                                                 \
> > })
> > 
> > This one I atleast got to compile, but I'm not very well versed with _Generic,
> > so this could definitely use some comments.
> 
> If you go this way, make _Generic() use simple in the macro with a help of two
> additional functions (per type). Also you need to take care about uid2 type to
> be _any_ unsigned integer. Or if you want to complicate things, then you need
> to distinguish signed and unsigned cases.

My initial thought was to have separate functions per type, but then
I realized it would become an unnecessary inconvenience to maintain
one per type. Having it inline with _Generic would make it relatively
easier, but I'll leave it to the maintainers to decide.

> P.S.
> All to me it seems way too overengineered w/o any potential prospective user.

I found a couple of acpi_dev_uid_to_integer() usages which could be
simplified with this implementation, but let's see how everyone feels
about this.

Thanks for the comments,
Raag