Re: [PATCH] iio: core: fail early in iio_device_alloc() if we can't get a device id

[Jonathan Cameron <jic23@kernel.org>]

On Thu, 16 Apr 2020 15:33:31 +0300
Alexandru Ardelean <alexandru.ardelean@analog.com> wrote:

> This change moves the 'ida_simple_get()' call to be the first one in
> iio_device_alloc(). It cleans up the error path a bit as we don't need to
> call any kfree(dev) anymore. We allocate an IIO device only if we have
> managed to obtain a device ID.

We just threw away an ID if the kzalloc then fails (or am I missing something?)
With that fixed I can't see this as being much of an improvement.
Either way one allocation needs to be tidied up.

Jonathan

> 
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> ---
>  drivers/iio/industrialio-core.c | 19 ++++++++++---------
>  1 file changed, 10 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index f4daf19f2a3b..7c1d8a3ab2f3 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -1494,6 +1494,14 @@ struct iio_dev *iio_device_alloc(int sizeof_priv)
>  {
>  	struct iio_dev *dev;
>  	size_t alloc_size;
> +	int id;
> +
> +	id = ida_simple_get(&iio_ida, 0, 0, GFP_KERNEL);
> +	if (id < 0) {
> +		/* cannot use a dev_err as the name isn't available */
> +		pr_err("failed to get device id\n");
> +		return NULL;
> +	}
>  
>  	alloc_size = sizeof(struct iio_dev);
>  	if (sizeof_priv) {
> @@ -1506,6 +1514,8 @@ struct iio_dev *iio_device_alloc(int sizeof_priv)
>  	dev = kzalloc(alloc_size, GFP_KERNEL);
>  
>  	if (dev) {
> +		dev->id = id;
> +		dev_set_name(&dev->dev, "iio:device%d", dev->id);
>  		dev->dev.groups = dev->groups;
>  		dev->dev.type = &iio_device_type;
>  		dev->dev.bus = &iio_bus_type;
> @@ -1514,15 +1524,6 @@ struct iio_dev *iio_device_alloc(int sizeof_priv)
>  		mutex_init(&dev->mlock);
>  		mutex_init(&dev->info_exist_lock);
>  		INIT_LIST_HEAD(&dev->channel_attr_list);
> -
> -		dev->id = ida_simple_get(&iio_ida, 0, 0, GFP_KERNEL);
> -		if (dev->id < 0) {
> -			/* cannot use a dev_err as the name isn't available */
> -			pr_err("failed to get device id\n");
> -			kfree(dev);
> -			return NULL;
> -		}
> -		dev_set_name(&dev->dev, "iio:device%d", dev->id);
>  		INIT_LIST_HEAD(&dev->buffer_list);
>  	}
>