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Date: Fri, 4 Sep 2020 11:14:04 +0000
From: "Pop, Cristian" <Cristian.Pop@...log.com>
To: Jonathan Cameron <jic23@...nel.org>
CC: "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [RFC PATCH v2] iio: core: Add optional symbolic label to a device
channel
Best ragards,
Cristian Pop
> -----Original Message-----
> From: Jonathan Cameron <jic23@...nel.org>
> Sent: Sunday, August 30, 2020 2:24 PM
> To: Pop, Cristian <Cristian.Pop@...log.com>
> Cc: linux-iio@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: Re: [RFC PATCH v2] iio: core: Add optional symbolic label to a device
> channel
>
> [External]
>
> On Mon, 24 Aug 2020 11:36:46 +0300
> Cristian Pop <cristian.pop@...log.com> wrote:
>
> > If a label is defined in the device tree for this channel add that to
> > the channel specific attributes. This is useful for userspace to be
> > able to identify an individual channel.
> >
> > Signed-off-by: Cristian Pop <cristian.pop@...log.com>
> > ---
> > Changes in v2:
> > - Move label check before "read_raw" callback.
> > - Move the responsability to of parsing channel labels, to the
> > driver.
> >
> > drivers/iio/industrialio-core.c | 10 ++++++++--
> > include/linux/iio/iio.h | 2 ++
> > include/linux/iio/types.h | 1 +
> > 3 files changed, 11 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/iio/industrialio-core.c
> > b/drivers/iio/industrialio-core.c index 1527f01a44f1..32277e94f02d
> > 100644
> > --- a/drivers/iio/industrialio-core.c
> > +++ b/drivers/iio/industrialio-core.c
> > @@ -135,6 +135,7 @@ static const char * const iio_modifier_names[] = {
> > /* relies on pairs of these shared then separate */ static const
> > char * const iio_chan_info_postfix[] = {
> > [IIO_CHAN_INFO_RAW] = "raw",
> > + [IIO_CHAN_INFO_LABEL] = "label",
> > [IIO_CHAN_INFO_PROCESSED] = "input",
> > [IIO_CHAN_INFO_SCALE] = "scale",
> > [IIO_CHAN_INFO_OFFSET] = "offset",
> > @@ -653,14 +654,18 @@ static ssize_t iio_read_channel_info(struct device
> *dev,
> > int ret;
> > int val_len = 2;
> >
> > - if (indio_dev->info->read_raw_multi)
> > + if (indio_dev->info->read_raw_multi) {
> > ret = indio_dev->info->read_raw_multi(indio_dev, this_attr-
> >c,
> >
> INDIO_MAX_RAW_ELEMENTS,
> > vals, &val_len,
> > this_attr->address);
> > - else
> > + } else {
> > ret = indio_dev->info->read_raw(indio_dev, this_attr->c,
> > &vals[0], &vals[1], this_attr->address);
> > + if (ret < 0 && this_attr->address == IIO_CHAN_INFO_LABEL
> &&
> > + this_attr->c->label_name)
>
> I'm not keen on this. We shouldn't be calling read_raw at all in this path.
> There is no way it can return a valid label.
>
> > + return sprintf(buf, "%s\n", this_attr->c->label_name);
> > + }
> >
> > if (ret < 0)
> > return ret;
> > @@ -1399,6 +1404,7 @@ static int iio_device_register_sysfs(struct iio_dev
> *indio_dev)
> > attrcount_orig++;
> > }
> > attrcount = attrcount_orig;
> > +
>
> Please avoid unrelated white space changes.
>
> > /*
> > * New channel registration method - relies on the fact a group does
> > * not need to be initialized if its name is NULL.
> > diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h index
> > a1be82e74c93..39209f3b62be 100644
> > --- a/include/linux/iio/iio.h
> > +++ b/include/linux/iio/iio.h
> > @@ -223,6 +223,7 @@ struct iio_event_spec {
> > * correspond to the first name that the channel is
> referred
> > * to by in the datasheet (e.g. IND), or the nearest
> > * possible compound name (e.g. IND-INC).
> > + * @label_name: Unique name to identify which channel this is.
> > * @modified: Does a modifier apply to this channel. What
> these are
> > * depends on the channel type. Modifier is set in
> > * channel2. Examples are IIO_MOD_X for axial sensors
> about
> > @@ -260,6 +261,7 @@ struct iio_chan_spec {
> > const struct iio_chan_spec_ext_info *ext_info;
> > const char *extend_name;
> > const char *datasheet_name;
> > + const char *label_name;
>
> This can't be part of chan_spec as that is constant in many drivers.
> We need a separate way of doing this. Don't use info_mask, but register it
> separately for each channel in a similar way to we do the name and label
> attributes for the whole device.
>
If "label_name" can't be part of the "struct iio_chan_spec " why would I pass
it to the callback function? Just identify the channel?
I would implement a callback :
int (*read_string)(struct iio_dev *indio_dev,
const struct iio_chan_spec *chan, const char *buf, long info);
and use this callback for other purposes as well, not only for "label" attribute.
> I would add a new callback to iio_info that is passed the iio_chan_spec and
> returns a const char * for the label name.
>
> The driver would be responsible for doing a lookup based on what it has
> cached from the dt parse, probably indexed off address or scan_index (that
> can be driver specific)
>
> To create the attribute you need to add this to iio_device_register_sysfs and
> use the various core functions to build the attribute name in a similar fashion
> to that done for info mask elements.
>
> It will be more complex than your approach, but make it more 'separable' as a
> feature in drivers.
>
> Jonathan
>
>
> > unsigned modified:1;
> > unsigned indexed:1;
> > unsigned output:1;
> > diff --git a/include/linux/iio/types.h b/include/linux/iio/types.h
> > index e6fd3645963c..c8f65f476eb2 100644
> > --- a/include/linux/iio/types.h
> > +++ b/include/linux/iio/types.h
> > @@ -34,6 +34,7 @@ enum iio_available_type {
> >
> > enum iio_chan_info_enum {
> > IIO_CHAN_INFO_RAW = 0,
> > + IIO_CHAN_INFO_LABEL,
> > IIO_CHAN_INFO_PROCESSED,
> > IIO_CHAN_INFO_SCALE,
> > IIO_CHAN_INFO_OFFSET,
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