On Tue, Jul 14, 2026 at 12:02:46PM +0100, Rodrigo Alencar via B4 Relay wrote:
> Move logic to create a channel prefix for naming attribute files into a
> separate __iio_chan_prefix_emit() function for reuse. The dev pointer is
> passed to __iio_device_attr_init() so that dev_err() replaces WARN().
> The new helper is going to be used to expose channel relationships as
> sysfs attributes.
...
> +static ssize_t __iio_chan_prefix_emit(struct device *dev,
> + const struct iio_chan_spec *chan,
> + enum iio_shared_by shared_by,
> + char *buf, size_t len)
> +{
> + const char *type = iio_chan_type_name_spec[chan->type];
> + const char *dir = iio_direction[chan->output];
> + struct seq_buf s;
> +
> + seq_buf_init(&s, buf, len);
> +
> + switch (shared_by) {
> + case IIO_SHARED_BY_ALL:
> + break;
> + case IIO_SHARED_BY_DIR:
> + seq_buf_printf(&s, "%s", dir);
> + break;
> + case IIO_SHARED_BY_TYPE:
> + seq_buf_printf(&s, "%s_%s", dir, type);
> + if (chan->differential)
> + seq_buf_printf(&s, "-%s", type);
> + break;
> + case IIO_SEPARATE:
> + seq_buf_printf(&s, "%s_%s", dir, type);
> + if (chan->indexed) {
> + seq_buf_printf(&s, "%d", chan->channel);
> + if (chan->differential)
> + seq_buf_printf(&s, "-%s%d", type,
> chan->channel2);
> + } else if (chan->differential) {
> + dev_err(dev, "Differential channels must be indexed\n");
> + return -EINVAL;
> + }
> +
> + if (chan->modified) {
> + if (chan->differential) {
> + dev_err(dev, "Differential channels can not
> have modifier\n");
> + return -EINVAL;
> + }
> + seq_buf_printf(&s, "_%s",
> iio_modifier_names[chan->channel2]);
> + }
> +
> + if (chan->extend_name)
> + seq_buf_printf(&s, "_%s", chan->extend_name);
> + break;
Can we actually do the validation first without dirtying the output?
/* Validate differential channel settings */
if (chan->differential) {
if (!chan->indexed) {
dev_err(dev, "Differential channels must be
indexed\n");
return -EINVAL;
}
if (chan->modified) {
dev_err(dev, "Differential channels can not
have modifier\n");
return -EINVAL;
}
}
seq_buf_printf(&s, "%s_%s", dir, type);
if (chan->indexed) {
seq_buf_printf(&s, "%d", chan->channel);
if (chan->differential)
seq_buf_printf(&s, "-%s%d", type, chan->channel2);
if (chan->modified)
seq_buf_printf(&s, "_%s",
iio_modifier_names[chan->channel2]);
if (chan->extend_name)
seq_buf_printf(&s, "_%s", chan->extend_name);
break;
> + }
> +
> + return seq_buf_has_overflowed(&s) ? -EOVERFLOW : s.len;
> +}
--
With Best Regards,
Andy Shevchenko
