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Fri, 07 Aug 2026 02:47:14 -0700 (PDT) From: Mohamad Raizudeen To: andriy.shevchenko@intel.com, jic23@kernel.org, dlechner@baylibre.com, andy@kernel.org, nuno.sa@analog.com Cc: gregkh@linuxfoundation.org, joshua.crofts1@gmail.com, skhan@linuxfoundation.org, me@brighamcampbell.com, jkoolstra@xs4all.nl, linux-iio@vger.kernel.org, linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org, Mohamad Raizudeen Subject: [PATCH v4] staging: iio: frequency: ad9832/ad9834: add comment explaining do_div usage Date: Fri, 7 Aug 2026 15:17:03 +0530 Message-ID: <20260807094704.5371-1-raizudeen.kerneldev@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-staging@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Previous attempts to change do_div() to div64_ul were rejected because mclk will always fit within 32 fits 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 --- Changes in v4: - Fixed typo in comment (fir -> fit) as pointed out by Joshua Crofts. drivers/staging/iio/frequency/ad9832.c | 6 ++++++ drivers/staging/iio/frequency/ad9834.c | 6 ++++++ 2 files changed, 12 insertions(+) diff --git a/drivers/staging/iio/frequency/ad9832.c b/drivers/staging/iio/frequency/ad9832.c index 60c33e10c46f..2e216c950c53 100644 --- a/drivers/staging/iio/frequency/ad9832.c +++ b/drivers/staging/iio/frequency/ad9832.c @@ -118,6 +118,12 @@ 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. + */ do_div(freqreg, mclk); return freqreg; } diff --git a/drivers/staging/iio/frequency/ad9834.c b/drivers/staging/iio/frequency/ad9834.c index 33dfd723923c..e089a94db97d 100644 --- a/drivers/staging/iio/frequency/ad9834.c +++ b/drivers/staging/iio/frequency/ad9834.c @@ -103,6 +103,12 @@ 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 a 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. + */ do_div(freqreg, mclk); return freqreg; } -- 2.53.0