Re: [PATCH v5 20/21] hwmon: (mr75203) add debugfs to read and write temperature coefficients

[Farber, Eliav]

On 9/14/2022 5:08 PM, Andy Shevchenko wrote:
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> On Wed, Sep 14, 2022 at 05:03:09PM +0300, Andy Shevchenko wrote:
> > On Wed, Sep 14, 2022 at 12:32:47PM +0300, Andy Shevchenko wrote:
> > > On Wed, Sep 14, 2022 at 07:26:36AM +0300, Farber, Eliav wrote:
> > > > On 9/13/2022 8:01 PM, Andy Shevchenko wrote:
> > > > > On Tue, Sep 13, 2022 at 05:40:16PM +0300, Farber, Eliav wrote:
> > > > > > On 9/13/2022 4:06 PM, Farber, Eliav wrote:
>
> ...
>
> > > > > > It seems like debugfs_attr_write() calls simple_attr_write() 
> > and it uses
> > > > > > kstrtoull(), which is why it fails when setting a negative 
> > value.
> > > > > > This is the same also in v6.0-rc5.
> > > > > >
> > > > > > debugfs_attr_read() on the other hand does show the correct 
> > value also
> > > > > > when j is negative.
> > > > >
> > > > > Which puzzles me since there is a few drivers that use %lld.
> > > > > Yeah, changing it to
> > > > >
> > > > >        ret = sscanf(attr->set_buf, attr->fmt, &val);
> > > > >        if (ret != 1)
> > > > >                ret = -EINVAL;
> > > > >
> > > > > probably can fix that. Dunno if debugfs maintainer is okay with 
> > this.
> > > > >
> > > > > P.S. This needs revisiting all format strings to see if there 
> > are no
> > > > > additional
> > > > > characters, otherwise that needs to be addressed first, if 
> > feasible.
> > > >
> > > > I was thinking of making such a correction:
> > > >
> > > > -       ret = kstrtoull(attr->set_buf, 0, &val);
> > > > +       if (attr->set_buf[0] == '-')
> > > > +               ret = kstrtoll(attr->set_buf, 0, &val);
> > > > +       else
> > > > +               ret = kstrtoull(attr->set_buf, 0, &val);
> > > >
> > > > and when I tested the change it worked, but then I noticed this 
> > commit:
> > > >
> > > > 
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/fs/libfs.c?h=v6.0-rc5&id=488dac0c9237647e9b8f788b6a342595bfa40bda
> > > >
> > > > According to this, it previously used simple_strtoll() which 
> > supports
> > > > negative values, but was changed to use kstrtoull() to deliberately
> > > > return '-EINVAL' if it gets a negative value.
> > > >
> > > > So I’m not sure debugfs maintainers will be okay with a fix that
> > > > basically reverts the commit I mentioned.
> > > > Hence, what do you suggest to do with my commit?
> > > > Is it ok to leave it as it is today?
> > >
> > > Meanwhile asking is not a problem, at least we will know for sure.
> > > And yes, leave it as is, but point to the thread where you asking
> > > the clarification.
> >
> > For the record:
> >
> > $ git grep -n -A1 -w DEFINE_DEBUGFS_ATTRIBUTE | grep ');' | sed 
> > 's,.*\(".*%.*"\).*,\1,' | sort | uniq -c
> >   1 "%08llx\n"
> >   5 "0x%016llx\n"
> >   5 "0x%02llx\n"
> >   5 "0x%04llx\n"
> >  13 "0x%08llx\n"
> >   1 "0x%4.4llx\n"
> >   3 "0x%.4llx\n"
> >   4 "0x%llx\n"
> >   1 "%1lld\n"
> >  40 "%lld\n"
> >   2 "%lli\n"
> > 129 "%llu\n"
> >   1 "%#llx\n"
> >   2 "%llx\n"
> >
> > means that sscanf() should work and fix the issue. You may even 
> > propose a patch
> > as a starter for a discussion.


I proposed a patch with the fix you suggested.

--
Thanks, Eliav