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

[Jonathan Cameron <jic23@kernel.org>]

On Mon, 18 May 2026 14:56:06 +0100
Rodrigo Alencar <455.rodrigo.alencar@gmail.com> wrote:

> On 26/05/17 06:56PM, sashiko-bot@kernel.org wrote:
> > 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.  
> 
> Maybe -EINVAL can be returned for that case indeed. For a debug interface I
> did not see that as a problem.
Agreed - I don't see this as important either way.
>  
> > -- 
> > Sashiko AI review · https://sashiko.dev/#/patchset/20260517-ad9910-iio-driver-v5-0-31599c88314a@analog.com?part=2  
>