On 18/06/26 16:06, Nuno Sá wrote:
> On Thu, Jun 18, 2026 at 02:27:22PM +0100, Rodrigo Alencar via B4 Relay wrote:
> > From: Rodrigo Alencar <[email protected]>
> >
> > Move logic to create a channel prefix for naming attribute files into a
> > separate __iio_chan_prefix_emit() function for reuse.
...
> > +static int __iio_chan_prefix_emit(const struct iio_chan_spec *chan,
> > + enum iio_shared_by shared_by,
> > + char *buf, size_t len)
> > +{
> > + const char *dir = iio_direction[chan->output];
> > + const char *type = iio_chan_type_name_spec[chan->type];
> > + int n = 0;
> > +
> > + switch (shared_by) {
> > + case IIO_SHARED_BY_ALL:
> > + buf[0] = '\0'; /* empty channel prefix */
> > + break;
> > + case IIO_SHARED_BY_DIR:
> > + n = scnprintf(buf, len, "%s", dir);
> > + break;
> > + case IIO_SHARED_BY_TYPE:
> > + n = scnprintf(buf, len, "%s_%s", dir, type);
> > + if (chan->differential)
> > + n += scnprintf(buf + n, len - n, "-%s", type);
> > + break;
> > + case IIO_SEPARATE:
> > + if (chan->indexed) {
> > + n = scnprintf(buf, len, "%s_%s%d", dir, type,
> > + chan->channel);
> > + if (chan->differential)
> > + n += scnprintf(buf + n, len - n, "-%s%d", type,
> > + chan->channel2);
> > + } else {
> > + if (chan->differential) {
> > + WARN(1, "Differential channels must be
> > indexed\n");
> > + return -EINVAL;
> > + }
> > + n = scnprintf(buf, len, "%s_%s", dir, type);
> > + }
> > +
> > + if (chan->modified) {
> > + if (chan->differential) {
> > + WARN(1, "Differential channels can not have
> > modifier\n");
> > + return -EINVAL;
>
> WARN() looks too much to me. dev_error() as we're treating it as such. I
> guess you don't want to pass struct device but not really an issue IMHO.
__iio_device_attr_init() also used WARN(), probably because it didnt have
access to a dev pointer. It would not be a problem to add an extra param.
>
> > + }
> > + n += scnprintf(buf + n, len - n, "_%s",
> > + iio_modifier_names[chan->channel2]);
> > + }
> > +
> > + if (chan->extend_name)
> > + n += scnprintf(buf + n, len - n, "_%s",
> > chan->extend_name);
> > + break;
> > + }
> > +
> > + if (n > 0 && n < len - 1) { /* prefix termination if not empty */
> > + buf[n++] = '_';
> > + buf[n] = '\0';
> > + }
> > +
>
> Can't we handle the above in the caller on kasprintf()? Then we could
> simplify and return in place.
I felt like doing this here would get a cleaner logic in the caller, which
would have to add the '_' conditionally.
>
> > + return n;
> > +}
> > +
> > /**
> > * iio_device_id() - query the unique ID for the device
> > * @indio_dev: Device structure whose ID is being queried
> > @@ -1100,106 +1159,19 @@ int __iio_device_attr_init(struct device_attribute
> > *dev_attr,
> > size_t len),
> > enum iio_shared_by shared_by)
> > {
> > - int ret = 0;
> > - char *name = NULL;
> > - char *full_postfix;
> > + char prefix[NAME_MAX + 1];
> > + int ret;
> >
> > sysfs_attr_init(&dev_attr->attr);
> >
> > - /* Build up postfix of <extend_name>_<modifier>_postfix */
> > - if (chan->modified && (shared_by == IIO_SEPARATE)) {
> > - if (chan->extend_name)
> > - full_postfix = kasprintf(GFP_KERNEL, "%s_%s_%s",
> > -
> > iio_modifier_names[chan->channel2],
> > - chan->extend_name,
> > - postfix);
> > - else
> > - full_postfix = kasprintf(GFP_KERNEL, "%s_%s",
> > -
> > iio_modifier_names[chan->channel2],
> > - postfix);
> > - } else {
> > - if (chan->extend_name == NULL || shared_by != IIO_SEPARATE)
> > - full_postfix = kstrdup(postfix, GFP_KERNEL);
> > - else
> > - full_postfix = kasprintf(GFP_KERNEL,
> > - "%s_%s",
> > - chan->extend_name,
> > - postfix);
> > - }
> > - if (full_postfix == NULL)
> > + ret = __iio_chan_prefix_emit(chan, shared_by, prefix, sizeof(prefix));
> > + if (ret < 0)
> > + return ret;
> > +
> > + dev_attr->attr.name = kasprintf(GFP_KERNEL, "%s%s", prefix, postfix);
> > + if (!dev_attr->attr.name)
> > return -ENOMEM;
>
> I don't oppose the change. Looks like a nice cleanup. But bear in mind
> this very sensible as any subtle mistake means ABI breakage.
Yes! I tried to be careful... this is dangerous stuff!
--
Kind regards,
Rodrigo Alencar
