linux-kernel - Re: [PATCH 1/1] tools: iio: fix iio_generic

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Message-ID: <20240107170026.6baccc49@jic23-huawei>
Date: Sun, 7 Jan 2024 17:00:26 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Petre Rodan <petre.rodan@...dimension.ro>
Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, Lars-Peter
 Clausen <lars@...afoo.de>
Subject: Re: [PATCH 1/1] tools: iio: fix iio_generic_buffer

On Sun, 7 Jan 2024 18:28:52 +0200
Petre Rodan <petre.rodan@...dimension.ro> wrote:

> Hi Jonathan,
> 
> On Sun, Jan 07, 2024 at 03:53:33PM +0000, Jonathan Cameron wrote:
> > On Thu,  4 Jan 2024 12:12:45 +0200
> > Petre Rodan <petre.rodan@...dimension.ro> wrote:
> >   
> > > Fix code flow problem and floating point exception caused by improper
> > > directory stream positioning.
> > > 
> > > Fixes: <e58537ccce733> ("staging: iio: update example application.")
> > > Signed-off-by: Petre Rodan <petre.rodan@...dimension.ro>  
> > Hi Petre,
> > 
> > This doesn't really explain 'why' seeekdir(dp, 0) is wrong.
> > My assumption is that telldir() would not have returned 0 on this particular
> > system?  Could you confirm that and update the message to explain why
> > seekdir(dp, 0) is not equivalent to rewinddir(dp).  
> 
> it looks like there is a 32-bit specific bug in one of the glibc patches that
> the stable Gentoo Linux is using [1]. telldir returns (u32)(-1) if seekdir is
> used which ends up in a floating point exception.
> 
> it so happens that the rewinddir() function (which is equivalent) works
> correctly. so it is a fix for Gentoo users and should not impact anyone else.
> 
> [1] https://sourceware.org/bugzilla/show_bug.cgi?id=31212
> 
> my very best regards,
> peter

I'd be happy to take the same change as a cleanup if you want to resubmit it
with a different patch description.

Thanks,

Jonathan

> 
> > Thanks,
> > 
> > Jonathan
> >   
> > > ---
> > >  tools/iio/iio_utils.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/tools/iio/iio_utils.c b/tools/iio/iio_utils.c
> > > index 6a00a6eecaef..c5c5082cb24e 100644
> > > --- a/tools/iio/iio_utils.c
> > > +++ b/tools/iio/iio_utils.c
> > > @@ -376,7 +376,7 @@ int build_channel_array(const char *device_dir, int buffer_idx,
> > >  		goto error_close_dir;
> > >  	}
> > > 
> > > -	seekdir(dp, 0);
> > > +	rewinddir(dp);
> > >  	while (ent = readdir(dp), ent) {
> > >  		if (strcmp(ent->d_name + strlen(ent->d_name) - strlen("_en"),
> > >  			   "_en") == 0) {
> > > --
> > > 2.41.0