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

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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 :)




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