Re: [PATCH v3 08/11] iio: buffer: wrap all buffer attributes into iio_dev_attr

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Mon, 1 Feb 2021 16:51:02 +0200
Alexandru Ardelean <alexandru.ardelean@analog.com> wrote:

> This change wraps all buffer attributes into iio_dev_attr objects, and
> assigns a reference to the IIO buffer they belong to.
> 
> With the addition of multiple IIO buffers per one IIO device, we need a way
> to know which IIO buffer is being enabled/disabled/controlled.
> 
> We know that all buffer attributes are device_attributes. So we can wrap
> them with a iio_dev_attr types. In the iio_dev_attr type, we can also hold
> a reference to an IIO buffer.
> So, we end up being able to allocate wrapped attributes for all buffer
> attributes (even the one from other drivers).
> 
> The neat part with this mechanism, is that we don't need to add any extra
> cleanup, because these attributes are being added to a dynamic list that
> will get cleaned up via iio_free_chan_devattr_list().


> 
> With this change, the 'buffer->scan_el_dev_attr_list' list is being renamed
> to 'buffer->buffer_attr_list', effectively merging (or finalizing the
> merge) of the buffer/ & scan_elements/ attributes internally.
> 
> Accessing these new buffer attributes can now be done via
> 'to_iio_dev_attr(attr)->buffer' inside the show/store handlers.

That is going to look a bit odd in any drivers that use it given they
will appear to not be embedded.

There seem to be very few such attributes from a quick grep, so maybe
we may want to unwind this and change all the types.   Might still need
to set .buffer for some of them though (only applying to new drivers as
clearly current ones don't care!)

Looking at what they actually are, some perhaps shouldn't have been in the buffer
directory in the first place (with hindsight!).

Anyhow, aside from that oddity this looks good to me.

Jonathan

> 
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> ---
>  drivers/iio/industrialio-buffer.c | 66 +++++++++++++++++++++----------
>  include/linux/iio/buffer_impl.h   |  4 +-
>  2 files changed, 48 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
> index a525e88b302f..49996bed5f4c 100644
> --- a/drivers/iio/industrialio-buffer.c
> +++ b/drivers/iio/industrialio-buffer.c
> @@ -448,7 +448,7 @@ static int iio_buffer_add_channel_sysfs(struct iio_dev *indio_dev,
>  				     IIO_SEPARATE,
>  				     &indio_dev->dev,
>  				     buffer,
> -				     &buffer->scan_el_dev_attr_list);
> +				     &buffer->buffer_attr_list);
>  	if (ret)
>  		return ret;
>  	attrcount++;
> @@ -460,7 +460,7 @@ static int iio_buffer_add_channel_sysfs(struct iio_dev *indio_dev,
>  				     0,
>  				     &indio_dev->dev,
>  				     buffer,
> -				     &buffer->scan_el_dev_attr_list);
> +				     &buffer->buffer_attr_list);
>  	if (ret)
>  		return ret;
>  	attrcount++;
> @@ -473,7 +473,7 @@ static int iio_buffer_add_channel_sysfs(struct iio_dev *indio_dev,
>  					     0,
>  					     &indio_dev->dev,
>  					     buffer,
> -					     &buffer->scan_el_dev_attr_list);
> +					     &buffer->buffer_attr_list);
>  	else
>  		ret = __iio_add_chan_devattr("en",
>  					     chan,
> @@ -483,7 +483,7 @@ static int iio_buffer_add_channel_sysfs(struct iio_dev *indio_dev,
>  					     0,
>  					     &indio_dev->dev,
>  					     buffer,
> -					     &buffer->scan_el_dev_attr_list);
> +					     &buffer->buffer_attr_list);
>  	if (ret)
>  		return ret;
>  	attrcount++;
> @@ -495,8 +495,7 @@ static ssize_t iio_buffer_read_length(struct device *dev,
>  				      struct device_attribute *attr,
>  				      char *buf)
>  {
> -	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> -	struct iio_buffer *buffer = indio_dev->buffer;
> +	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
>  
>  	return sprintf(buf, "%d\n", buffer->length);
>  }
> @@ -506,7 +505,7 @@ static ssize_t iio_buffer_write_length(struct device *dev,
>  				       const char *buf, size_t len)
>  {
>  	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> -	struct iio_buffer *buffer = indio_dev->buffer;
> +	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
>  	unsigned int val;
>  	int ret;
>  
> @@ -538,8 +537,7 @@ static ssize_t iio_buffer_show_enable(struct device *dev,
>  				      struct device_attribute *attr,
>  				      char *buf)
>  {
> -	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> -	struct iio_buffer *buffer = indio_dev->buffer;
> +	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
>  
>  	return sprintf(buf, "%d\n", iio_buffer_is_active(buffer));
>  }
> @@ -1154,7 +1152,7 @@ static ssize_t iio_buffer_store_enable(struct device *dev,
>  	int ret;
>  	bool requested_state;
>  	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> -	struct iio_buffer *buffer = indio_dev->buffer;
> +	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
>  	bool inlist;
>  
>  	ret = strtobool(buf, &requested_state);
> @@ -1185,8 +1183,7 @@ static ssize_t iio_buffer_show_watermark(struct device *dev,
>  					 struct device_attribute *attr,
>  					 char *buf)
>  {
> -	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> -	struct iio_buffer *buffer = indio_dev->buffer;
> +	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
>  
>  	return sprintf(buf, "%u\n", buffer->watermark);
>  }
> @@ -1197,7 +1194,7 @@ static ssize_t iio_buffer_store_watermark(struct device *dev,
>  					  size_t len)
>  {
>  	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> -	struct iio_buffer *buffer = indio_dev->buffer;
> +	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
>  	unsigned int val;
>  	int ret;
>  
> @@ -1230,8 +1227,7 @@ static ssize_t iio_dma_show_data_available(struct device *dev,
>  						struct device_attribute *attr,
>  						char *buf)
>  {
> -	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> -	struct iio_buffer *buffer = indio_dev->buffer;
> +	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
>  
>  	return sprintf(buf, "%zu\n", iio_buffer_data_available(buffer));
>  }
> @@ -1256,6 +1252,26 @@ static struct attribute *iio_buffer_attrs[] = {
>  	&dev_attr_data_available.attr,
>  };
>  
> +#define to_dev_attr(_attr) container_of(_attr, struct device_attribute, attr)
> +
> +static struct attribute *iio_buffer_wrap_attr(struct iio_buffer *buffer,
> +					      struct attribute *attr)
> +{
> +	struct device_attribute *dattr = to_dev_attr(attr);
> +	struct iio_dev_attr *iio_attr;
> +
> +	iio_attr = kzalloc(sizeof(*iio_attr), GFP_KERNEL);
> +	if (!iio_attr)
> +		return NULL;
> +
> +	iio_attr->buffer = buffer;
> +	memcpy(&iio_attr->dev_attr, dattr, sizeof(iio_attr->dev_attr));
> +
> +	list_add(&iio_attr->l, &buffer->buffer_attr_list);
> +
> +	return &iio_attr->dev_attr.attr;
> +}
> +
>  static int iio_buffer_register_legacy_sysfs_groups(struct iio_dev *indio_dev,
>  						   struct attribute **buffer_attrs,
>  						   int buffer_attrcount,
> @@ -1331,7 +1347,7 @@ static int __iio_buffer_alloc_sysfs_and_mask(struct iio_buffer *buffer,
>  	}
>  
>  	scan_el_attrcount = 0;
> -	INIT_LIST_HEAD(&buffer->scan_el_dev_attr_list);
> +	INIT_LIST_HEAD(&buffer->buffer_attr_list);
>  	channels = indio_dev->channels;
>  	if (channels) {
>  		/* new magic */
> @@ -1378,9 +1394,19 @@ static int __iio_buffer_alloc_sysfs_and_mask(struct iio_buffer *buffer,
>  
>  	buffer_attrcount += ARRAY_SIZE(iio_buffer_attrs);
>  
> -	attrn = buffer_attrcount;
> +	for (i = 0; i < buffer_attrcount; i++) {
> +		struct attribute *wrapped;
> +
> +		wrapped = iio_buffer_wrap_attr(buffer, attr[i]);
> +		if (!wrapped) {
> +			ret = -ENOMEM;
> +			goto error_free_scan_mask;
> +		}
> +		attr[i] = wrapped;
> +	}
>  
> -	list_for_each_entry(p, &buffer->scan_el_dev_attr_list, l)
> +	attrn = 0;
> +	list_for_each_entry(p, &buffer->buffer_attr_list, l)
>  		attr[attrn++] = &p->dev_attr.attr;
>  
>  	buffer->buffer_group.name = kasprintf(GFP_KERNEL, "buffer%d", index);
> @@ -1412,7 +1438,7 @@ static int __iio_buffer_alloc_sysfs_and_mask(struct iio_buffer *buffer,
>  error_free_scan_mask:
>  	bitmap_free(buffer->scan_mask);
>  error_cleanup_dynamic:
> -	iio_free_chan_devattr_list(&buffer->scan_el_dev_attr_list);
> +	iio_free_chan_devattr_list(&buffer->buffer_attr_list);
>  
>  	return ret;
>  }
> @@ -1443,7 +1469,7 @@ static void __iio_buffer_free_sysfs_and_mask(struct iio_buffer *buffer)
>  	bitmap_free(buffer->scan_mask);
>  	kfree(buffer->buffer_group.name);
>  	kfree(buffer->buffer_group.attrs);
> -	iio_free_chan_devattr_list(&buffer->scan_el_dev_attr_list);
> +	iio_free_chan_devattr_list(&buffer->buffer_attr_list);
>  }
>  
>  void iio_buffer_free_sysfs_and_mask(struct iio_dev *indio_dev)
> diff --git a/include/linux/iio/buffer_impl.h b/include/linux/iio/buffer_impl.h
> index 3e555e58475b..41044320e581 100644
> --- a/include/linux/iio/buffer_impl.h
> +++ b/include/linux/iio/buffer_impl.h
> @@ -97,8 +97,8 @@ struct iio_buffer {
>  	/* @scan_timestamp: Does the scan mode include a timestamp. */
>  	bool scan_timestamp;
>  
> -	/* @scan_el_dev_attr_list: List of scan element related attributes. */
> -	struct list_head scan_el_dev_attr_list;
> +	/* @buffer_attr_list: List of buffer attributes. */
> +	struct list_head buffer_attr_list;
>  
>  	/*
>  	 * @buffer_group: Attributes of the new buffer group.