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Date:   Sun, 26 Apr 2020 10:45:38 +0100
From:   Jonathan Cameron <jic23@kernel.org>
To:     Alexandru Ardelean <alexandru.ardelean@analog.com>
Cc:     <linux-iio@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <lars@metafoo.de>
Subject: Re: [RFC PATCH 1/4] iio: Move scan mask management to the core
Message-ID: <20200426104538.657a2d9a@archlinux>
In-Reply-To: <20200424051818.6408-2-alexandru.ardelean@analog.com>
References: <20200424051818.6408-1-alexandru.ardelean@analog.com>
        <20200424051818.6408-2-alexandru.ardelean@analog.com>
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On Fri, 24 Apr 2020 08:18:15 +0300
Alexandru Ardelean <alexandru.ardelean@analog.com> wrote:

> From: Lars-Peter Clausen <lars@metafoo.de>
> 
> Let the core handle the buffer scan mask management including allocation
> and channel selection. Having this handled in a central place rather than
> open-coding it all over the place will make it easier to change the
> implementation.
> 
> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>

Hi Alex,

For some reason I only have patch 1 of this series of 4.

This one looks reasonable to me as abstracts away how it is implemented
which is good. A few comments and a question inline.

Jonathan


> ---
>  drivers/iio/buffer/industrialio-buffer-cb.c | 17 ++++------
>  drivers/iio/industrialio-buffer.c           | 36 +++++++++++++++------
>  drivers/iio/inkern.c                        | 15 +++++++++
>  include/linux/iio/consumer.h                | 10 ++++++
>  4 files changed, 58 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/iio/buffer/industrialio-buffer-cb.c b/drivers/iio/buffer/industrialio-buffer-cb.c
> index 47c96f7f4976..b50f1f48cac6 100644
> --- a/drivers/iio/buffer/industrialio-buffer-cb.c
> +++ b/drivers/iio/buffer/industrialio-buffer-cb.c
> @@ -33,8 +33,7 @@ static int iio_buffer_cb_store_to(struct iio_buffer *buffer, const void *data)
>  static void iio_buffer_cb_release(struct iio_buffer *buffer)
>  {
>  	struct iio_cb_buffer *cb_buff = buffer_to_cb_buffer(buffer);
> -
> -	bitmap_free(cb_buff->buffer.scan_mask);
> +	iio_buffer_free_scanmask(buffer);
>  	kfree(cb_buff);
>  }
>  
> @@ -72,27 +71,25 @@ struct iio_cb_buffer *iio_channel_get_all_cb(struct device *dev,
>  	}
>  
>  	cb_buff->indio_dev = cb_buff->channels[0].indio_dev;
> -	cb_buff->buffer.scan_mask = bitmap_zalloc(cb_buff->indio_dev->masklength,
> -						  GFP_KERNEL);
> -	if (cb_buff->buffer.scan_mask == NULL) {
> -		ret = -ENOMEM;
> +
> +	ret = iio_buffer_alloc_scanmask(&cb_buff->buffer, cb_buff->indio_dev);
> +	if (ret)
>  		goto error_release_channels;
> -	}
> +
>  	chan = &cb_buff->channels[0];
>  	while (chan->indio_dev) {
>  		if (chan->indio_dev != cb_buff->indio_dev) {
>  			ret = -EINVAL;
>  			goto error_free_scan_mask;
>  		}
> -		set_bit(chan->channel->scan_index,
> -			cb_buff->buffer.scan_mask);
> +		iio_buffer_channel_enable(&cb_buff->buffer, chan);
>  		chan++;
>  	}
>  
>  	return cb_buff;
>  
>  error_free_scan_mask:
> -	bitmap_free(cb_buff->buffer.scan_mask);
> +	iio_buffer_free_scanmask(&cb_buff->buffer);
>  error_release_channels:
>  	iio_channel_release_all(cb_buff->channels);
>  error_free_cb_buff:
> diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
> index 221157136af6..c06691281287 100644
> --- a/drivers/iio/industrialio-buffer.c
> +++ b/drivers/iio/industrialio-buffer.c
> @@ -206,6 +206,26 @@ void iio_buffer_init(struct iio_buffer *buffer)
>  }
>  EXPORT_SYMBOL(iio_buffer_init);
>  
> +int iio_buffer_alloc_scanmask(struct iio_buffer *buffer,
> +			      struct iio_dev *indio_dev)
I'm not sure passing the indio_dev in here makes sense as it
obscures that all we are getting from it is the masklength.
May be better to pass that explicitly.

> +{
> +	if (!indio_dev->masklength)
> +		return 0;

This is a bit of an oddity of the old code.  Any idea why we
allow things to continue with a masklength of 0?  Seems to me
that it is thoroughly broken if that occurs!

> +
> +	buffer->scan_mask = bitmap_zalloc(indio_dev->masklength, GFP_KERNEL);
> +	if (buffer->scan_mask == NULL)
> +		return -ENOMEM;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(iio_buffer_alloc_scanmask);
> +
> +void iio_buffer_free_scanmask(struct iio_buffer *buffer)
> +{
> +	bitmap_free(buffer->scan_mask);
> +}
> +EXPORT_SYMBOL_GPL(iio_buffer_free_scanmask);
> +
>  /**
>   * iio_buffer_set_attrs - Set buffer specific attributes
>   * @buffer: The buffer for which we are setting attributes
> @@ -1301,14 +1321,10 @@ int iio_buffer_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
>  				indio_dev->scan_index_timestamp =
>  					channels[i].scan_index;
>  		}
> -		if (indio_dev->masklength && buffer->scan_mask == NULL) {
> -			buffer->scan_mask = bitmap_zalloc(indio_dev->masklength,
> -							  GFP_KERNEL);
> -			if (buffer->scan_mask == NULL) {
> -				ret = -ENOMEM;
> -				goto error_cleanup_dynamic;
> -			}
> -		}
> +
> +		ret = iio_buffer_alloc_scanmask(buffer, indio_dev);
> +		if (ret)
> +			goto error_cleanup_dynamic;
>  	}
>  
>  	buffer->scan_el_group.name = iio_scan_elements_group_name;
> @@ -1329,7 +1345,7 @@ int iio_buffer_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
>  	return 0;
>  
>  error_free_scan_mask:
> -	bitmap_free(buffer->scan_mask);
> +	iio_buffer_free_scanmask(buffer);
>  error_cleanup_dynamic:
>  	iio_free_chan_devattr_list(&buffer->scan_el_dev_attr_list);
>  	kfree(indio_dev->buffer->buffer_group.attrs);
> @@ -1342,7 +1358,7 @@ void iio_buffer_free_sysfs_and_mask(struct iio_dev *indio_dev)
>  	if (!indio_dev->buffer)
>  		return;
>  
> -	bitmap_free(indio_dev->buffer->scan_mask);
> +	iio_buffer_free_scanmask(indio_dev->buffer);
>  	kfree(indio_dev->buffer->buffer_group.attrs);
>  	kfree(indio_dev->buffer->scan_el_group.attrs);
>  	iio_free_chan_devattr_list(&indio_dev->buffer->scan_el_dev_attr_list);
> diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
> index ede99e0d5371..f35cb9985edc 100644
> --- a/drivers/iio/inkern.c
> +++ b/drivers/iio/inkern.c
> @@ -11,6 +11,7 @@
>  
>  #include <linux/iio/iio.h>
>  #include "iio_core.h"
> +#include <linux/iio/buffer_impl.h>
>  #include <linux/iio/machine.h>
>  #include <linux/iio/driver.h>
>  #include <linux/iio/consumer.h>
> @@ -857,6 +858,20 @@ int iio_write_channel_raw(struct iio_channel *chan, int val)
>  }
>  EXPORT_SYMBOL_GPL(iio_write_channel_raw);
>  
> +void iio_buffer_channel_enable(struct iio_buffer *buffer,
> +			       const struct iio_channel *chan)
> +{
> +	set_bit(chan->channel->scan_index, buffer->scan_mask);
> +}
> +EXPORT_SYMBOL_GPL(iio_buffer_channel_enable);
> +
> +void iio_buffer_channel_disable(struct iio_buffer *buffer,
> +				const struct iio_channel *chan)
> +{
> +	clear_bit(chan->channel->scan_index, buffer->scan_mask);
> +}
> +EXPORT_SYMBOL_GPL(iio_buffer_channel_disable);
> +
>  unsigned int iio_get_channel_ext_info_count(struct iio_channel *chan)
>  {
>  	const struct iio_chan_spec_ext_info *ext_info;
> diff --git a/include/linux/iio/consumer.h b/include/linux/iio/consumer.h
> index c4118dcb8e05..dbc87c26250a 100644
> --- a/include/linux/iio/consumer.h
> +++ b/include/linux/iio/consumer.h
> @@ -12,6 +12,7 @@
>  
>  struct iio_dev;
>  struct iio_chan_spec;
> +struct iio_buffer;
>  struct device;
>  
>  /**
> @@ -342,6 +343,15 @@ int iio_read_channel_scale(struct iio_channel *chan, int *val,
>  int iio_convert_raw_to_processed(struct iio_channel *chan, int raw,
>  	int *processed, unsigned int scale);
>  
> +void iio_buffer_channel_enable(struct iio_buffer *buffer,
> +			       const struct iio_channel *chan);
> +void iio_buffer_channel_disable(struct iio_buffer *buffer,
> +				const struct iio_channel *chan);
> +
> +int iio_buffer_alloc_scanmask(struct iio_buffer *buffer,
> +			      struct iio_dev *indio_dev);
> +void iio_buffer_free_scanmask(struct iio_buffer *buffer);
> +
>  /**
>   * iio_get_channel_ext_info_count() - get number of ext_info attributes
>   *				      connected to the channel.