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Message-ID: <20250706115003.5752261c@jic23-huawei> Date: Sun, 6 Jul 2025 11:50:03 +0100 From: Jonathan Cameron <jic23@...nel.org> To: akshay bansod <akbansd@...il.com> Cc: Andy Shevchenko <andriy.shevchenko@...el.com>, Lorenzo Bianconi <lorenzo@...nel.org>, David Lechner <dlechner@...libre.com>, Nuno Sá <nuno.sa@...log.com>, Andy Shevchenko <andy@...nel.org>, linux-kernel-mentees@...ts.linuxfoundation.org, skhan@...uxfoundation.org, linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v2] iio: st_lsm6dsx: Replace scnprintf with sysfs_emit On Thu, 03 Jul 2025 22:28:13 +0530 akshay bansod <akbansd@...il.com> wrote: > On Thursday, 3 July 2025 10:12 pm +0530 Andy Shevchenko wrote: > > On Thu, Jul 03, 2025 at 11:08:59AM +0530, Akshay Bansod wrote: > > > Update the sysfs interface for sampling frequency and scale attributes. > > > Replace `scnprintf()` with `sysfs_emit_at()` which is PAGE_SIZE-aware > > > and recommended for use in sysfs. > > > > 'must' is stronger than 'recommendation'. > > Of has the documentation been changed lately? > > > > ... > > > > > st_lsm6dsx_sysfs_sampling_frequency_avail(struct device *dev, > > > > > odr_table = &sensor->hw->settings->odr_table[sensor->id]; > > > for (i = 0; i < odr_table->odr_len; i++) > > > - len += scnprintf(buf + len, PAGE_SIZE - len, "%d.%03d ", > > > - odr_table->odr_avl[i].milli_hz / 1000, > > > - odr_table->odr_avl[i].milli_hz % 1000); > > > + len += sysfs_emit_at(buf, len, "%d.%03d ", > > > + odr_table->odr_avl[i].milli_hz / 1000, > > > + odr_table->odr_avl[i].milli_hz % 1000); > > > buf[len - 1] = '\n'; > > > > My gosh, this is error prone. I'm wondering when some CIs will start to > > complain on this line. But this was already before your change... > > > I'm planning to drop It entirely or should I replace it with another `sysfs_emit_at()` ? > I've seen other device driver returning space terminated buffers. Maybe I'm overlooking > something. It is rather ugly currently but not a bug as such as we know we don't actually run out of space in the page (it would just overwrite last byte in that case so odd output, but not a bug) and that we always print something so just as you suggest sysfs_emit_at(buf, len - 1, "\n"); is safe. It also checks under and overflow so that safe + hopefully won't trip up static analysis tools. > > > > return len; > > > > ... > > > > > fs_table = &hw->settings->fs_table[sensor->id]; > > > for (i = 0; i < fs_table->fs_len; i++) > > > - len += scnprintf(buf + len, PAGE_SIZE - len, "0.%09u ", > > > - fs_table->fs_avl[i].gain); > > > + len += sysfs_emit_at(buf, len, "0.%09u ", > > > + fs_table->fs_avl[i].gain); > > > buf[len - 1] = '\n'; > > > > Ditto. > > > > > > regards, > Akshay Bansod > > > >
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