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

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Message-ID: <20231027142856.GL3208943@black.fi.intel.com>
Date:   Fri, 27 Oct 2023 17:28:56 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Raag Jadav <raag.jadav@...el.com>
Cc:     rafael@...nel.org, len.brown@...el.com,
        andriy.shevchenko@...ux.intel.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 Fri, Oct 27, 2023 at 05:17:12PM +0300, Raag Jadav wrote:
> On Fri, Oct 27, 2023 at 01:12:02PM +0300, Raag Jadav wrote:
> > On Fri, Oct 27, 2023 at 11:18:55AM +0300, Mika Westerberg wrote:
> > > On Thu, Oct 26, 2023 at 02:03:35PM +0530, Raag Jadav wrote:
> > > > Now that we have a standard ACPI helper, we can use acpi_dev_uid_match()
> > > > for matching _UID as per the original logic before commit 2a036e489eb1
> > > > ("ACPI: LPSS: Refactor _UID handling to use acpi_dev_uid_to_integer()"),
> > > > instead of treating it as an integer.
> > > > 
> > > > Signed-off-by: Raag Jadav <raag.jadav@...el.com>
> > > > Acked-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> > > 
> > > The change still looks good to me, however I wonder if we could maybe
> > > improve acpi_dev_uid_match() to support both data types possible for
> > > _UID? This of course is separate patch (unless there are objections).
> > > 
> > > There is the _Generic() thing and I think that can be used to make
> > > 
> > >   acpi_dev_uid_match()
> > > 
> > > which takes either u64 (or maybe even unsigned int) or const char * and
> > > based on that picks the correct implementation. Not sure if that's
> > > possible, did not check but it would allow us to use one function
> > > everywhere instead of acpi_dev_uid_to_integer() and
> > > acpi_dev_uid_match().
> > 
> > The way I see it, acpi_dev_uid_to_integer() is useful when drivers want to
> > parse _UID and store it in their private data, so that it is available for
> > making various decisions throughout the lifetime of the driver, as opposed
> > to acpi_dev_uid_match() which is more useful for oneshot comparisons in my
> > opinion.
> > 
> > So I'm a bit conflicted about merging them into a single helper, unless
> > ofcourse there is a way to serve both purposes.
> 
> Or perhaps something like,
> 
> bool acpi_dev_uid_match(struct acpi_device *adev, const void *uid2, enum uid_type type)
> {
>         u64 uid1_d, uid2_d;
> 
>         if (type == UID_TYPE_STR) {
>                 char *uid2_s = (char *)uid2;
>                 if (!(uid2_s && !kstrtou64(uid2_s, 0, &uid2_d)))
>                         return false;
>         } else if (type == UID_TYPE_INT) {
>                 u64 *uid2_p;
>                 uid2_p = (u64 *)uid2;
>                 uid2_d = *uid2_p;
>         } else {
>                 return false;
>         }
> 
>         if (!acpi_dev_uid_to_integer(adev, &uid1_d) && uid1_d == uid2_d)
>                 return true;
>         else
>                 return false;
> }
> 
> Although this looks unnecessarily hideous.

Indeed, but using the _Generic() you should be able to have
a single acpi_dev_uid_match() to work for either type so:

acpi_dev_uid_match(adev, "1")

and

acpi_dev_uid_match(adev, 1)

would both work with type checkings etc.

Not sure if this is worth the trouble though.