Re: [PATCH v2 5/5] Input: evdev - Switch to bitmap_zalloc()

[Joe Perches]

On Mon, 2018-06-18 at 15:02 +0300, Andy Shevchenko wrote:
> On Sat, 2018-06-16 at 12:16 -0700, Joe Perches wrote:
> > On Sat, 2018-06-16 at 21:45 +0300, Andy Shevchenko wrote:
> > > On Sat, Jun 16, 2018 at 12:46 AM Yury Norov <ynorov@xxxxxxxxxxxxxxxx
> > > om> wrote:
> > > > On Fri, Jun 15, 2018 at 04:20:17PM +0300, Andy Shevchenko wrote:
> > > > > Switch to bitmap_zalloc() to show clearly what we are
> > > > > allocating.
> > > > > Besides that it returns pointer of bitmap type instead of opaque
> > > > > void *.
> > > 
> > > 
> > > > > +       mem = bitmap_alloc(maxbit, GFP_KERNEL);
> > > > >         if (!mem)
> > > > >                 return -ENOMEM;
> > > > 
> > > > But in commit message you say you switch to bitmap_zalloc(). IIUC
> > > > bitmap_alloc() is OK here. But could you please update comment to
> > > > avoid confusing.
> > > 
> > > There are two places, one with alloc, another with zalloc.
> > > I will clarify this in commit message of next version.
> > > 
> > > > > +       mask = bitmap_zalloc(cnt, GFP_KERNEL);
> > > > >         if (!mask)
> > > > >                 return -ENOMEM;
> > > > > 
> > > > >         error = bits_from_user(mask, cnt - 1, codes_size, codes,
> > > > > compat);
> > > > 
> > > > If my understanding of bits_from_user() correct, here you can also
> > > > use
> > > > bitmap_alloc(), true?
> > 
> > Also it might be useful to have a separate bitmap_from_user
> > to alloc and copy.
> 
> Maybe. I didn't check if there are such users except this driver.
> 
> Anyway, it's out of scope of the series.

That seems incorrect as you are introducing alloc/free helpers.

Perhaps bitmap_dup_user [or some better name] could or should
be one of the helpers.