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From: Andy Shevchenko <andriy.shevchenko@intel.com>
To: Joshua Crofts <joshua.crofts1@gmail.com>
Cc: David Laight <david.laight.linux@gmail.com>,
	lars@metafoo.de, Michael.Hennerich@analog.com, jic23@kernel.org,
	greghk@linuxfoundation.org, dlechner@baylibre.com,
	nono.sa@analog.com, andy@kernel.org, linux-iio@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-staging@lists.linux.dev
Subject: Re: [PATCH] iio: frequency: ad983x: replace do_div() with div64_ul().
Date: Fri, 10 Apr 2026 07:30:04 +0300	[thread overview]
Message-ID: <adh8zOCQDhGwgf0Y@ashevche-desk.local> (raw)
In-Reply-To: <CALoEA-yVCyyiA1gUCj4Z0JcLscpSSssPCPXnUPOciWJOHj3VUg@mail.gmail.com>

On Thu, Apr 09, 2026 at 09:58:20PM +0200, Joshua Crofts wrote:
> On Thu, 9 Apr 2026 at 19:27, David Laight <david.laight.linux@gmail.com> wrote:
> > Except here you have clock frequencies.
> > Either they fit in 32bits or they don't.
> > So the value shouldn't be 'unsigned long', but either u32 or u64.
> 
> The clk struct in linux/clk.h explicitly uses an unsigned long to represent
> the clock value, which is used in this driver. Using an unsigned long
> ensures platform independent usage without type mismatching.

...which effectively means the frequency most likely fits 32-bit. Otherwise
would it ever work on 32-bit platform? This is a mistake in CLK design.

> > You need to check the domain of the values, coccinelle is just looking
> > at the types.
> > Even with mclk being 'unsigned long' the code is fine provided the
> > frequency is below 4.2GHz.
> 
> I agree that we're not dealing with potential truncation problems, however
> changing to div64_ul aligns the types with the clk API and scrubs a perfectly
> valid cocci error.

-- 
With Best Regards,
Andy Shevchenko



  parent reply	other threads:[~2026-04-10  4:30 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-04-09 13:18 [PATCH] iio: frequency: ad983x: replace do_div() with div64_ul() Joshua Crofts
2026-04-09 13:34 ` Joshua Crofts
2026-04-09 14:52   ` Greg KH
2026-04-09 15:01     ` [PATCH v2] " Joshua Crofts
2026-04-09 15:39       ` David Lechner
2026-04-09 15:50         ` Andy Shevchenko
2026-04-09 15:49 ` [PATCH] " Andy Shevchenko
2026-04-09 17:27 ` David Laight
2026-04-09 19:58   ` Joshua Crofts
2026-04-09 21:46     ` David Laight
2026-04-10  4:30     ` Andy Shevchenko [this message]
2026-04-10  6:58       ` Joshua Crofts
2026-04-10  8:11         ` David Laight

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