On Mon, 27 Jul 2026 10:40:55 +0100 Rodrigo Alencar <[email protected]> wrote:
> On 25/07/26 23:24, Jonathan Cameron wrote: > > On Wed, 22 Jul 2026 16:50:17 +0100 > > Rodrigo Alencar via B4 Relay > > <[email protected]> wrote: > > > > > From: Rodrigo Alencar <[email protected]> > > > > > > Add parent-child relationship between iio channels by creating a parent > > > pointer field in iio_chan_spec struct and exposing a sysfs attribute that > > > returns the parent channel prefix. > > > > > > Signed-off-by: Rodrigo Alencar <[email protected]> > > Hi Rodrigo. > > > > One small thing below > > > > Jonathan > > > > > --- > > > drivers/iio/industrialio-core.c | 40 > > > ++++++++++++++++++++++++++++++++++++++++ > > > include/linux/iio/iio.h | 5 +++++ > > > 2 files changed, 45 insertions(+) > > > > > > diff --git a/drivers/iio/industrialio-core.c > > > b/drivers/iio/industrialio-core.c > > > index aa9d6474edd9..f7e3048354b9 100644 > > > --- a/drivers/iio/industrialio-core.c > > > +++ b/drivers/iio/industrialio-core.c > > > @@ -856,6 +856,22 @@ static ssize_t iio_read_channel_label(struct device > > > *dev, > > > to_iio_dev_attr(attr)->c, buf); > > > } > > > > > > +static ssize_t iio_read_channel_parent(struct device *dev, > > > + struct device_attribute *attr, > > > + char *buf) > > > +{ > > > + const struct iio_chan_spec *chan = to_iio_dev_attr(attr)->c->parent; > > > + ssize_t len; > > > + > > > + len = __iio_chan_prefix_emit(dev, chan, IIO_SEPARATE, buf, PAGE_SIZE); > > > + if (len < 0) > > > + return len; > > > + > > > + buf[len++] = '\n'; > > > > Use sysfs_emit_at() for this rather than a direct write. I'd rather not have > > to think about what happens if __iio_chan_prefix_emit() returns exactly > > PAGE_SIZE(). > > We can have __iio_chan_prefix_emit() called with PAGE_SIZE - 1? That seems sensible anyway. > > Filenames should be capped at 255.. so that NAME_MAX << PAGE_SIZE Agreed it isn't a real issue but nice to tidy up anyway. > > As you suggest, we need a local buffer. Not sure we need to do an extra > copy... I'm lost. I'm only suggesting sysfs_emit_at() for the buf[len++] = '\n'; not eh more complex __iio_chan_prefix_emit() as that takes the size so anyone reading just this snippet will assume it doesn't overflow. Jonathan > > > > + > > > + return len; > > > +} > > > + >
