linux-kernel - Re: [PATCH 1/2] iio: Add iio_read_channel

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Date: Sun, 23 Jun 2024 13:03:39 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Sean Anderson <sean.anderson@...ux.dev>
Cc: Jean Delvare <jdelvare@...e.com>, Guenter Roeck <linux@...ck-us.net>,
 linux-iio@...r.kernel.org, linux-hwmon@...r.kernel.org, Lars-Peter Clausen
 <lars@...afoo.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] iio: Add iio_read_channel_label to inkern API

On Thu, 20 Jun 2024 17:13:08 -0400
Sean Anderson <sean.anderson@...ux.dev> wrote:

> It can be convenient for other in-kernel drivers to reuse IIO channel
> labels. Export the iio_read_channel_label function to allow this. The
> signature is different depending on where we are calling it from, so
> the meat is moved to do_iio_read_channel_label.
> 
> Signed-off-by: Sean Anderson <sean.anderson@...ux.dev>

Seems like a useful addition to me. I'm not 100% what path this will
take so if it goes via HWMON.

Acked-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

It may be messy and need an immutable branch however. I haven't
checked for churn in this code yet.


> ---
> 
>  drivers/iio/iio_core.h          |  4 ++++
>  drivers/iio/industrialio-core.c | 23 ++++++++++++++---------
>  drivers/iio/inkern.c            |  6 ++++++
>  include/linux/iio/consumer.h    | 10 ++++++++++
>  4 files changed, 34 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/iio/iio_core.h b/drivers/iio/iio_core.h
> index 1a38b1915e7a..b7d5f4f0fada 100644
> --- a/drivers/iio/iio_core.h
> +++ b/drivers/iio/iio_core.h
> @@ -34,6 +34,10 @@ void iio_device_ioctl_handler_register(struct iio_dev *indio_dev,
>  				       struct iio_ioctl_handler *h);
>  void iio_device_ioctl_handler_unregister(struct iio_ioctl_handler *h);
>  
> +ssize_t do_iio_read_channel_label(struct iio_dev *indio_dev,
> +				  const struct iio_chan_spec *c,
> +				  char *buf);
> +
>  int __iio_add_chan_devattr(const char *postfix,
>  			   struct iio_chan_spec const *chan,
>  			   ssize_t (*func)(struct device *dev,
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index 2f185b386949..0f6cda7ffe45 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -727,22 +727,27 @@ ssize_t iio_format_value(char *buf, unsigned int type, int size, int *vals)
>  }
>  EXPORT_SYMBOL_GPL(iio_format_value);
>  
> -static ssize_t iio_read_channel_label(struct device *dev,
> -				      struct device_attribute *attr,
> -				      char *buf)
> +ssize_t do_iio_read_channel_label(struct iio_dev *indio_dev,
> +				  const struct iio_chan_spec *c,
> +				  char *buf)
>  {
> -	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 indio_dev->info->read_label(indio_dev, this_attr->c, buf);
> +		return indio_dev->info->read_label(indio_dev, c, buf);
>  
> -	if (this_attr->c->extend_name)
> -		return sysfs_emit(buf, "%s\n", this_attr->c->extend_name);
> +	if (c->extend_name)
> +		return sysfs_emit(buf, "%s\n", c->extend_name);
>  
>  	return -EINVAL;
>  }
>  
> +static ssize_t iio_read_channel_label(struct device *dev,
> +				      struct device_attribute *attr,
> +				      char *buf)
> +{
> +	return do_iio_read_channel_label(dev_to_iio_dev(dev),
> +					 to_iio_dev_attr(attr)->c, buf);
> +}
> +
>  static ssize_t iio_read_channel_info(struct device *dev,
>  				     struct device_attribute *attr,
>  				     char *buf)
> diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
> index 39cf26d69d17..9f484c94bc6e 100644
> --- a/drivers/iio/inkern.c
> +++ b/drivers/iio/inkern.c
> @@ -1010,3 +1010,9 @@ ssize_t iio_write_channel_ext_info(struct iio_channel *chan, const char *attr,
>  			       chan->channel, buf, len);
>  }
>  EXPORT_SYMBOL_GPL(iio_write_channel_ext_info);
> +
> +ssize_t iio_read_channel_label(struct iio_channel *chan, char *buf)
> +{
> +	return do_iio_read_channel_label(chan->indio_dev, chan->channel, buf);
> +}
> +EXPORT_SYMBOL_GPL(iio_read_channel_label);
> diff --git a/include/linux/iio/consumer.h b/include/linux/iio/consumer.h
> index e9910b41d48e..333d1d8ccb37 100644
> --- a/include/linux/iio/consumer.h
> +++ b/include/linux/iio/consumer.h
> @@ -441,4 +441,14 @@ ssize_t iio_read_channel_ext_info(struct iio_channel *chan,
>  ssize_t iio_write_channel_ext_info(struct iio_channel *chan, const char *attr,
>  				   const char *buf, size_t len);
>  
> +/**
> + * iio_read_channel_label() - read label for a given channel
> + * @chan:		The channel being queried.
> + * @buf:		Where to store the attribute value. Assumed to hold
> + *			at least PAGE_SIZE bytes.
> + *
> + * Returns the number of bytes written to buf, or an error code.
> + */
> +ssize_t iio_read_channel_label(struct iio_channel *chan, char *buf);
> +
>  #endif