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From: Alexandru Ardelean <ardeleanalex@gmail.com>
To: Paul Cercueil <paul@crapouillou.net>
Cc: Jonathan Cameron <jic23@kernel.org>,
	Lars-Peter Clausen <lars@metafoo.de>,
	linux-iio <linux-iio@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 2/2] iio: core: Support reading extended name as label
Date: Thu, 17 Jun 2021 10:22:35 +0300	[thread overview]
Message-ID: <CA+U=DsrP6+Zjnca8Sqd0jAi9a4aDqAV4suJZc95ayqm7K0+mCw@mail.gmail.com> (raw)
In-Reply-To: <20210616155706.17444-3-paul@crapouillou.net>

On Wed, Jun 16, 2021 at 7:00 PM Paul Cercueil <paul@crapouillou.net> wrote:
>
> The point of this new change is to make the IIO tree actually parsable.
>
> Before, given this attribute as a filename:
> in_voltage0_aux_sample_rate
>
> Userspace had no way to know if the attribute name was
> "aux_sample_rate" with no extended name, or "sample_rate" with "aux" as
> the extended name, or just "rate" with "aux_sample" as the extended
> name.
>
> This was somewhat possible to deduce when there was more than one
> attribute present for a given channel, e.g:
> in_voltage0_aux_sample_rate
> in_voltage0_aux_frequency
>
> There, it was possible to deduce that "aux" was the extended name. But
> even with more than one attribute, this wasn't very robust, as two
> attributes starting with the same prefix (e.g. "sample_rate" and
> "sample_size") would result in the first part of the prefix being
> interpreted as being part of the extended name.
>
> To address the issue, knowing that channels will never have both a label
> and an extended name, set the channel's label to the extended name.
> In this case, the label's attribute will also have the extended name in
> its filename, but we can live with that - userspace can open
> in_voltage0_<prefix>_label and verify that it returns <prefix> to obtain
> the extended name.
>

The best way would have been for all drivers [using extend_name] to
implement their own read_label hook.
But this can work fine as well [as the other method would add some duplication].

> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
> ---
>  drivers/iio/industrialio-core.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index 81f40dab778a..9b37e96538c2 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -717,8 +717,12 @@ static ssize_t iio_read_channel_label(struct device *dev,
>         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
>         struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
>
> -       if (!indio_dev->info->read_label)
> -               return -EINVAL;
> +       if (!indio_dev->info->read_label) {
> +               if (this_attr->c->extend_name)
> +                       return sprintf(buf, "%s\n", this_attr->c->extend_name);
> +               else

nitpick: else statement has no effect

well, this block could be reworked a bit as:

----------------------------------------------------
if (indio_dev->info->read_label)
   return indio_dev->info->read_label(indio_dev, this_attr->c, buf);

if (this_attr->c->extend_name)
    return sprintf(buf, "%s\n", this_attr->c->extend_name);

return -EINVAL;
----------------------------------------------------


> +                       return -EINVAL;
> +       }
>
>         return indio_dev->info->read_label(indio_dev, this_attr->c, buf);
>  }
> @@ -1160,7 +1164,7 @@ static int iio_device_add_channel_label(struct iio_dev *indio_dev,
>         struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
>         int ret;
>
> -       if (!indio_dev->info->read_label)
> +       if (!indio_dev->info->read_label && !chan->extend_name)
>                 return 0;
>
>         ret = __iio_add_chan_devattr("label",
> --
> 2.30.2
>

  reply	other threads:[~2021-06-17  7:23 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-16 15:57 [PATCH v2 0/2] Add "extended_name" to label Paul Cercueil
2021-06-16 15:57 ` [PATCH v2 1/2] iio: core: Forbid use of both labels and extended names Paul Cercueil
2021-06-17  7:07   ` Alexandru Ardelean
2021-06-16 15:57 ` [PATCH v2 2/2] iio: core: Support reading extended name as label Paul Cercueil
2021-06-17  7:22   ` Alexandru Ardelean [this message]
2021-06-17  9:08     ` Paul Cercueil

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