Re: [PATCH v2 02/13] storage-by-alias: drop fake cdev

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

On 12/9/25 1:51 PM, Sascha Hauer wrote:
> storage-by-alias creates its own cdev, but that is never used. The only
> purpose is to create a cdev with its own device node which otherwise
> links to the original cdev. This means we can drop all the cdev
> operations and use the newly created devfs_create_link_node() with the
> same effect.
> 
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Reviewed-by: Ahmad Fatoum <a.fatoum@pengutronix.de>

> ---
>  drivers/misc/storage-by-alias.c | 120 +++-------------------------------------
>  1 file changed, 7 insertions(+), 113 deletions(-)
> 
> diff --git a/drivers/misc/storage-by-alias.c b/drivers/misc/storage-by-alias.c
> index 2c498e0d0483ca71093612382c78372df399c437..6c759867ccbb7a7b4bc922152699eb346d42d271 100644
> --- a/drivers/misc/storage-by-alias.c
> +++ b/drivers/misc/storage-by-alias.c
> @@ -24,102 +24,8 @@ static LIST_HEAD(sba_list);
>  struct sba {
>  	char *alias;
>  	struct device *dev;
> -	struct cdev *rcdev;
> -	struct cdev cdev;
>  	struct list_head list;
> -};
> -
> -static ssize_t sba_read(struct cdev *cdev, void *buf, size_t count, loff_t offset, ulong flags)
> -{
> -	struct sba *sba = cdev->priv;
> -
> -	return cdev_read(sba->rcdev, buf, count, offset, flags);
> -}
> -
> -static ssize_t sba_write(struct cdev *cdev, const void *buf, size_t count, loff_t offset, ulong flags)
> -{
> -	struct sba *sba = cdev->priv;
> -
> -	return cdev_write(sba->rcdev, buf, count, offset, flags);
> -}
> -
> -static int sba_ioctl(struct cdev *cdev, unsigned int request, void *buf)
> -{
> -	struct sba *sba = cdev->priv;
> -
> -	return cdev_ioctl(sba->rcdev, request, buf);
> -}
> -
> -static int sba_open(struct cdev *cdev, unsigned long flags)
> -{
> -	struct sba *sba = cdev->priv;
> -
> -	return cdev_open(sba->rcdev, flags);
> -}
> -
> -static int sba_close(struct cdev *cdev)
> -{
> -	struct sba *sba = cdev->priv;
> -
> -	cdev_close(sba->rcdev);
> -
> -	return 0;
> -}
> -
> -static int sba_flush(struct cdev *cdev)
> -{
> -	struct sba *sba = cdev->priv;
> -
> -	return cdev_flush(sba->rcdev);
> -}
> -
> -static int sba_erase(struct cdev *cdev, loff_t count, loff_t offset)
> -{
> -	struct sba *sba = cdev->priv;
> -
> -	return cdev_erase(sba->rcdev, count, offset);
> -}
> -
> -static int sba_protect(struct cdev *cdev, size_t count, loff_t offset, int prot)
> -{
> -	struct sba *sba = cdev->priv;
> -
> -	return cdev_protect(sba->rcdev, count, offset, prot);
> -}
> -
> -static int sba_discard_range(struct cdev *cdev, loff_t count, loff_t offset)
> -{
> -	struct sba *sba = cdev->priv;
> -
> -	return cdev_discard_range(sba->rcdev, count, offset);
> -}
> -
> -static int sba_memmap(struct cdev *cdev, void **map, int flags)
> -{
> -	struct sba *sba = cdev->priv;
> -
> -	return cdev_memmap(sba->rcdev, map, flags);
> -}
> -
> -static int sba_truncate(struct cdev *cdev, size_t size)
> -{
> -	struct sba *sba = cdev->priv;
> -
> -	return cdev_truncate(sba->rcdev, size);
> -}
> -
> -static struct cdev_operations sba_ops = {
> -	.read = sba_read,
> -	.write = sba_write,
> -	.ioctl = sba_ioctl,
> -	.open = sba_open,
> -	.close = sba_close,
> -	.flush = sba_flush,
> -	.erase = sba_erase,
> -	.protect = sba_protect,
> -	.discard_range = sba_discard_range,
> -	.memmap = sba_memmap,
> -	.truncate = sba_truncate,
> +	bool populated;
>  };
>  
>  static int sba_add_partitions(struct cdev *rcdev, void *data)
> @@ -127,29 +33,17 @@ static int sba_add_partitions(struct cdev *rcdev, void *data)
>  	struct sba *sba = data;
>  	int ret;
>  
> -	dev_dbg(sba->dev, "Adding %s -> %s\n", sba->alias, rcdev->name);
> -
> -	if (sba->rcdev)
> +	if (sba->populated)
>  		return 0;
>  
> -	sba->rcdev = rcdev;
> -	sba->cdev.link = rcdev;
> -	sba->cdev.name = sba->alias;
> -	sba->cdev.size = rcdev->size;
> -	sba->cdev.ops = &sba_ops;
> -	sba->cdev.dev = sba->dev;
> -	sba->cdev.priv = sba;
> +	dev_info(sba->dev, "Adding %s -> %s\n", sba->alias, rcdev->name);
>  
> -	if (rcdev->flags & DEVFS_WRITE_AUTOERASE)
> -		sba->cdev.flags |= DEVFS_WRITE_AUTOERASE;
> +	ret = devfs_create_link_node(rcdev, sba->alias, sba->dev->device_node);
> +	if (ret)
> +		return ret;
>  
> -	ret = devfs_create(&sba->cdev);
> -	if (ret) {
> -		dev_err(sba->dev, "Failed to create cdev: %pe\n", ERR_PTR(ret));
> -		return 0;
> -	}
> +	sba->populated = true;
>  
> -	of_parse_partitions(&sba->cdev, sba->dev->of_node);
>  	return 0;
>  }
>  
> 

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