Re: [PATCH] drivers: gpu: Fix warning using plain integer as NULL

[Abhinav Singh]

On 11/6/23 22:10, Jani Nikula wrote:
> On Mon, 06 Nov 2023, Abhinav Singh <singhabhinav9051571833@xxxxxxxxx> wrote:
> > On 11/6/23 16:53, Jani Nikula wrote:
> > > On Fri, 03 Nov 2023, Abhinav Singh <singhabhinav9051571833@xxxxxxxxx> wrote:
> > > > sparse static analysis tools generate a warning with this message
> > > > "Using plain integer as NULL pointer". In this case this warning is
> > > > being shown because we are trying to intialize a pointer to NULL using
> > > > integer value 0.
> > > >
> > > > Signed-off-by: Abhinav Singh <singhabhinav9051571833@xxxxxxxxx>
> > > > ---
> > > >    drivers/gpu/drm/radeon/clearstate_evergreen.h | 8 ++++----
> > > >    1 file changed, 4 insertions(+), 4 deletions(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/radeon/clearstate_evergreen.h b/drivers/gpu/drm/radeon/clearstate_evergreen.h
> > > > index 63a1ffbb3ced..3b645558f133 100644
> > > > --- a/drivers/gpu/drm/radeon/clearstate_evergreen.h
> > > > +++ b/drivers/gpu/drm/radeon/clearstate_evergreen.h
> > > > @@ -1049,7 +1049,7 @@ static const struct cs_extent_def SECT_CONTEXT_defs[] =
> > > >        {SECT_CONTEXT_def_5, 0x0000a29e, 5 },
> > > >        {SECT_CONTEXT_def_6, 0x0000a2a5, 56 },
> > > >        {SECT_CONTEXT_def_7, 0x0000a2de, 290 },
> > > > -    { 0, 0, 0 }
> > > > +    { NULL, 0, 0 }
> > >
> > > Random drive-by comment:
> > >
> > > I'd just use {} as the sentinel.
> > >
> > > BR,
> > > Jani.
> > >
> > > >    };
> > > >    static const u32 SECT_CLEAR_def_1[] =
> > > >    {
> > > > @@ -1060,7 +1060,7 @@ static const u32 SECT_CLEAR_def_1[] =
> > > >    static const struct cs_extent_def SECT_CLEAR_defs[] =
> > > >    {
> > > >        {SECT_CLEAR_def_1, 0x0000ffc0, 3 },
> > > > -    { 0, 0, 0 }
> > > > +    { NULL, 0, 0 }
> > > >    };
> > > >    static const u32 SECT_CTRLCONST_def_1[] =
> > > >    {
> > > > @@ -1070,11 +1070,11 @@ static const u32 SECT_CTRLCONST_def_1[] =
> > > >    static const struct cs_extent_def SECT_CTRLCONST_defs[] =
> > > >    {
> > > >        {SECT_CTRLCONST_def_1, 0x0000f3fc, 2 },
> > > > -    { 0, 0, 0 }
> > > > +    { NULL, 0, 0 }
> > > >    };
> > > >    static const struct cs_section_def evergreen_cs_data[] = {
> > > >        { SECT_CONTEXT_defs, SECT_CONTEXT },
> > > >        { SECT_CLEAR_defs, SECT_CLEAR },
> > > >        { SECT_CTRLCONST_defs, SECT_CTRLCONST },
> > > > -    { 0, SECT_NONE }
> > > > +    { NULL, SECT_NONE }
> > > >    };
> > > > --
> > > > 2.39.2
> > Hi, Thanks for dropping by and the suggestion. I thought of using NULL
> > instead of {} is because, first the warning itself says that 0 is used
> > to intialize pointers with NULL, and second due this link
> > https://www.spinics.net/lists/linux-sparse/msg10066.html where linus is
> > talking about not using 0 NULL intialization of pointer variable and he
> > thinks this is a legitimate issue and not some false positive
>
> But... {} is neither of those things. It's empty initialization instead
> of 0. It's valid in GCC and C23, and used all over the place in the
> kernel.
>
> BR,
> Jani.
If I understand correctly you want to me change from this "{ NULL, 
SECT_NONE }" to "{}" right? If yes, then according to what I read from 
some online, it is better to intialize variables especially pointer 
because in some cases a non initialized pointer doesnt always point to 
NULL. Not sure if this applies in kernel space as well. But yeah my 
knowledge is pretty limited in C in user space and in kernel space it is 
even more limited :)