Re: [PATCH v5 02/13] iio: core: support 64-bit register through debugfs

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Silent truncation of 64-bit values when written to a 32-bit register access function.
--

commit 64785a0c1416e2cf718b558aa7a2cc9ac39b2d81
Author: Rodrigo Alencar <rodrigo.alencar@analog.com>

iio: core: support 64-bit register through debugfs

This commit introduces a debugfs_reg64_access function pointer to iio_info
to allow 64-bit register reads and writes through debugfs. The file operation
callbacks are modified to prefer the 64-bit variant when available.

> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index e587aca79b8e7..5c8404efd0a56 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c

[ ... ]

> @@ -429,7 +439,7 @@ static ssize_t iio_debugfs_write_reg(struct file *file,
>  
>  	buf[ret] = '\0';
>  
> -	ret = sscanf(buf, "%i %i", &reg, &val);
> +	ret = sscanf(buf, "%i %lli", &reg, &val64);
>  
>  	switch (ret) {
>  	case 1:
> @@ -437,8 +447,12 @@ static ssize_t iio_debugfs_write_reg(struct file *file,
>  		break;
>  	case 2:
>  		iio_dev_opaque->cached_reg_addr = reg;
> -		ret = indio_dev->info->debugfs_reg_access(indio_dev, reg,
> -							  val, NULL);
> +		if (indio_dev->info->debugfs_reg64_access)
> +			ret = indio_dev->info->debugfs_reg64_access(indio_dev, reg,
> +								    val64, NULL);
> +		else
> +			ret = indio_dev->info->debugfs_reg_access(indio_dev, reg,
> +								  val64, NULL);

Could this introduce a regression where values are silently truncated if the
provided input exceeds 32 bits?

Since the input is now unconditionally parsed as a 64-bit integer, falling
back to debugfs_reg_access (which takes an unsigned int for writeval) will
implicitly cast val64. If a user provides a value larger than UINT_MAX to a
driver that only provides the 32-bit callback, it appears the value will be
truncated rather than rejected with an error like -EINVAL.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260517-ad9910-iio-driver-v5-0-31599c88314a@analog.com?part=2