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[90.182.112.124]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-495653c9d99sm133607895e9.12.2026.07.22.01.46.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Jul 2026 01:46:18 -0700 (PDT) Date: Wed, 22 Jul 2026 10:46:17 +0200 From: Joshua Crofts To: Mohamad Raizudeen Cc: jic23@kernel.org, dlechner@baylibre.com, andy@kernel.org, nuno.sa@analog.com, gregkh@linuxfoundation.org, skhan@linuxfoundation.org, me@brighamcampbell.com, jkoolstra@xs4all.nl, linux-iio@vger.kernel.org, linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org, Andy Shevchenko Subject: Re: [PATCH v2] staging: iio: frequency: ad9832/ad9834: add comment explaining do_div usage Message-ID: <20260722104617.000050fa@gmail.com> In-Reply-To: <20260722082227.18768-1-raizudeen.kerneldev@gmail.com> References: <20260630032322.5805-1-raizudeen.kerneldev@gmail.com> <20260722082227.18768-1-raizudeen.kerneldev@gmail.com> X-Mailer: Claws Mail 4.4.0 (GTK 3.24.51; x86_64-w64-mingw32) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 22 Jul 2026 13:52:27 +0530 Mohamad Raizudeen wrote: > Previous attempts to change do_div() to div64_ul() were rejected because > mclk will always fit within 32 bits for this hardware, making do_div() > safe to use. > > However, Coccinelle continues to flag this as a false positive. To > prevent future developers from submitting unnecessary fixes, add a > comment explaining why do_div() is intentionally kept. > > Suggested-by: Andy Shevchenko > Signed-off-by: Mohamad Raizudeen > --- Please don't send a new version as a reply to the previous version, as it can break tooling such as b4 for patch review. As for the comment, I think it's good, however I'm not sure whether this should be split into two patches, given that this is a small change. Andy, what do you think? > diff --git a/drivers/staging/iio/frequency/ad9832.c b/drivers/staging/iio/frequency/ad9832.c > index 60c33e10c46f..6d046e9121e2 100644 > --- a/drivers/staging/iio/frequency/ad9832.c > +++ b/drivers/staging/iio/frequency/ad9832.c > @@ -118,6 +118,13 @@ static unsigned long ad9832_calc_freqreg(unsigned long mclk, unsigned long fout) > { > u64 freqreg = (u64)fout << AD9832_FREQ_BITS; > > + /* > + * mclk is an unsigned long, which triggers a Coccinelle false positive > + * warning about using do_div() for 64-by-32 division. However, mclk > + * for this hardware will always fit within 32 bits, so do_div() is > + * safe to use here. > + */ > + Unnecessary blank line here, you want to couple the comment with the line that it's describing. > do_div(freqreg, mclk); > return freqreg; > } > diff --git a/drivers/staging/iio/frequency/ad9834.c b/drivers/staging/iio/frequency/ad9834.c > index 33dfd723923c..8722f3a01cde 100644 > --- a/drivers/staging/iio/frequency/ad9834.c > +++ b/drivers/staging/iio/frequency/ad9834.c > @@ -103,6 +103,13 @@ static unsigned int ad9834_calc_freqreg(unsigned long mclk, unsigned long fout) > { > unsigned long long freqreg = (u64)fout * (u64)BIT(AD9834_FREQ_BITS); > > + /* > + * mclk is an unsigned long, which triggers a Coccinelle false positive > + * warning about using do_div() for 64-by-32 division. However, mclk > + * for this hardware will always fit within 32 bits, so do_div() is > + * safe to use here. > + */ > + Ditto. > do_div(freqreg, mclk); > return freqreg; > } -- Kind regards, Joshua Crofts