linux-kernel - Re: [PATCH v1] ACPI: LPSS: use acpi_dev_uid_match() for matching

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Message-ID: <ZTnWSRIr1o7RLcOl@black.fi.intel.com>
Date:   Thu, 26 Oct 2023 06:00:25 +0300
From:   Raag Jadav <raag.jadav@...el.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     rafael@...nel.org, len.brown@...el.com,
        mika.westerberg@...ux.intel.com, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        mallikarjunappa.sangannavar@...el.com, bala.senthil@...el.com
Subject: Re: [PATCH v1] ACPI: LPSS: use acpi_dev_uid_match() for matching _UID

On Wed, Oct 25, 2023 at 11:33:40PM +0300, Andy Shevchenko wrote:
> On Wed, Oct 25, 2023 at 11:08:33AM +0530, Raag Jadav wrote:
> > Use acpi_dev_uid_match() for matching _UID instead of treating it
> > as an integer.
> 
> NAK. See below why.
> 
> ...
> 
> >  static void byt_pwm_setup(struct lpss_private_data *pdata)
> >  {
> > -	u64 uid;
> > -
> >  	/* Only call pwm_add_table for the first PWM controller */
> > -	if (acpi_dev_uid_to_integer(pdata->adev, &uid) || uid != 1)
> > +	if (!acpi_dev_uid_match(pdata->adev, "1"))
> 
> _UID by specification is a type of _string_. Yet, that string may represent an
> integer number. Now, how many variants of the strings can you imagine that may
> be interpreted as integer 1? I can tell about dozens.
> 
> With your change you restricted the all possible spectre of the 1
> representations to a single one. Have you checked ALL of the DSDTs
> for these platforms to say 'hey, all current tables uses "1" and
> this is not an issue'?

I'm not sure if I'm following you, this would basically invalidate every
usage of acpi_dev_hid_uid_match() helper across the driver.

Raag