linux-kernel - Re: [PATCH 1/5] iio: buffer-dmaengine: add dev-managed calls for buffer alloc/free

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Date:   Fri, 21 Feb 2020 12:21:15 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Alexandru Ardelean <alexandru.ardelean@...log.com>
Cc:     <linux-kernel@...r.kernel.org>, <linux-iio@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <robh+dt@...nel.org>
Subject: Re: [PATCH 1/5] iio: buffer-dmaengine: add dev-managed calls for
 buffer alloc/free

On Thu, 20 Feb 2020 17:03:13 +0200
Alexandru Ardelean <alexandru.ardelean@...log.com> wrote:

> Currently, when using a 'iio_dmaengine_buffer_alloc()', an matching call to
> 'iio_dmaengine_buffer_free()' must be made.
> 
> With this change, this can be avoided by using
> 'devm_iio_dmaengine_buffer_alloc()'. The buffer will get free'd via the
> device's devres handling.
> 
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@...log.com>
> ---
>  .../buffer/industrialio-buffer-dmaengine.c    | 70 +++++++++++++++++++
>  include/linux/iio/buffer-dmaengine.h          |  5 ++
>  2 files changed, 75 insertions(+)
> 
> diff --git a/drivers/iio/buffer/industrialio-buffer-dmaengine.c b/drivers/iio/buffer/industrialio-buffer-dmaengine.c
> index b129693af0fd..eff89037e3f5 100644
> --- a/drivers/iio/buffer/industrialio-buffer-dmaengine.c
> +++ b/drivers/iio/buffer/industrialio-buffer-dmaengine.c
> @@ -229,6 +229,76 @@ void iio_dmaengine_buffer_free(struct iio_buffer *buffer)
>  }
>  EXPORT_SYMBOL_GPL(iio_dmaengine_buffer_free);
>  
> +static void __devm_iio_dmaengine_buffer_free(struct device *dev, void *res)
> +{
> +	iio_dmaengine_buffer_free(*(struct iio_buffer **)res);
> +}
> +
> +/**
> + * devm_iio_dmaengine_buffer_alloc() - Resource-managed iio_dmaengine_buffer_alloc()
> + * @dev: Parent device for the buffer
> + * @channel: DMA channel name, typically "rx".
> + *
> + * This allocates a new IIO buffer which internally uses the DMAengine framework
> + * to perform its transfers. The parent device will be used to request the DMA
> + * channel.
> + *
> + * Once done using the buffer iio_dmaengine_buffer_free() should be used to
> + * release it.

Umm.  It really shouldn't!

> + */
> +struct iio_buffer *devm_iio_dmaengine_buffer_alloc(struct device *dev,
> +	const char *channel)
> +{
> +	struct iio_buffer **bufferp, *buffer;
> +
> +	bufferp = devres_alloc(__devm_iio_dmaengine_buffer_free,
> +			       sizeof(*bufferp), GFP_KERNEL);
> +	if (!bufferp)
> +		return ERR_PTR(-ENOMEM);
> +
> +	buffer = iio_dmaengine_buffer_alloc(dev, channel);
> +	if (!IS_ERR(buffer)) {
> +		*bufferp = buffer;
> +		devres_add(dev, bufferp);

From a flow point of view I'd prefer.

	if (IS_ERR(buffer) {
		devres_free(buferp)
		return buffer;
	}

	*bufferp = buffer;
	devres_add(dev, bufferp);

	return buffer;


> +	} else {
> +		devres_free(bufferp);
> +	}
> +
> +	return buffer;
> +}
> +EXPORT_SYMBOL_GPL(devm_iio_dmaengine_buffer_alloc);
> +
> +static int devm_iio_dmaengine_buffer_match(struct device *dev, void *res,
> +	void *data)
> +{
> +	struct iio_buffer **r = res;
> +
> +	if (!r || !*r) {
> +		WARN_ON(!r || !*r);
> +		return 0;
> +	}
> +
> +	return *r == data;
> +}
> +
> +/**
> + * devm_iio_dmaengine_buffer_free - iio_dmaengine_buffer_free
> + * @dev: Device this iio_buffer belongs to
> + * @buffer: The iio_buffer associated with the device
> + *
> + * Free buffer allocated with devm_iio_dmaengine_buffer_alloc().
> + */
> +void devm_iio_dmaengine_buffer_free(struct device *dev,
> +	struct iio_buffer *buffer)
> +{
> +	int rc;
> +
> +	rc = devres_release(dev, __devm_iio_dmaengine_buffer_free,
> +			    devm_iio_dmaengine_buffer_match, buffer);
> +	WARN_ON(rc);
> +}
> +EXPORT_SYMBOL_GPL(devm_iio_dmaengine_buffer_free);
> +
>  MODULE_AUTHOR("Lars-Peter Clausen <lars@...afoo.de>");
>  MODULE_DESCRIPTION("DMA buffer for the IIO framework");
>  MODULE_LICENSE("GPL");
> diff --git a/include/linux/iio/buffer-dmaengine.h b/include/linux/iio/buffer-dmaengine.h
> index b3a57444a886..8dcd973d76c1 100644
> --- a/include/linux/iio/buffer-dmaengine.h
> +++ b/include/linux/iio/buffer-dmaengine.h
> @@ -14,4 +14,9 @@ struct iio_buffer *iio_dmaengine_buffer_alloc(struct device *dev,
>  	const char *channel);
>  void iio_dmaengine_buffer_free(struct iio_buffer *buffer);
>  
> +struct iio_buffer *devm_iio_dmaengine_buffer_alloc(struct device *dev,
> +	const char *channel);
> +void devm_iio_dmaengine_buffer_free(struct device *dev,
> +	struct iio_buffer *buffer);
Please align parameters with opening bracket where possible.

Thanks,

Jonathan

> +
>  #endif