Received-SPF: pass (google.com: domain of linux-kernel+bounces-98012-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1;
Date: Sat, 9 Mar 2024 18:37:00 +0000
From: Jonathan Cameron <jic23@kernel.org>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>,
 linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, Lars-Peter Clausen
 <lars@metafoo.de>
Subject: Re: [PATCH v1 1/2] iio: core: Leave private pointer NULL when no
 private data supplied
Message-ID: <20240309183700.60133d78@jic23-huawei>
In-Reply-To: <20240304140650.977784-2-andriy.shevchenko@linux.intel.com>
References: <20240304140650.977784-1-andriy.shevchenko@linux.intel.com>
	<20240304140650.977784-2-andriy.shevchenko@linux.intel.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit

On Mon,  4 Mar 2024 16:04:32 +0200
Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:

> In iio_device_alloc() when size of the private data is 0,
> the private pointer is calculated to point behind the valid data.
> Leave it NULL when no private data supplied.
> 
> Fixes: 6d4ebd565d15 ("iio: core: wrap IIO device into an iio_dev_opaque object")
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

Fix is a strong word given any driver trying to access the pointer in this case
will be broken anyway.  I don't mind it being backported as it'll make bugs
easier to identify but I'm not rushing it in.

Otherwise seems like a sensible bit of tidying up.

Jonathan

> ---
>  drivers/iio/industrialio-core.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index 4302093b92c7..8684ba246969 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -1654,8 +1654,10 @@ struct iio_dev *iio_device_alloc(struct device *parent, int sizeof_priv)
>  		return NULL;
>  
>  	indio_dev = &iio_dev_opaque->indio_dev;
> -	indio_dev->priv = (char *)iio_dev_opaque +
> -		ALIGN(sizeof(struct iio_dev_opaque), IIO_DMA_MINALIGN);
> +
> +	if (sizeof_priv)
> +		indio_dev->priv = (char *)iio_dev_opaque +
> +			ALIGN(sizeof(*iio_dev_opaque), IIO_DMA_MINALIGN);
>  
>  	indio_dev->dev.parent = parent;
>  	indio_dev->dev.type = &iio_device_type;