[PATCH] drm/amd/display: avoid passing enum as NULL pointer

[Deucher, Alexander]

Thanks for the patch.  We already have the fix queued:
https://cgit.freedesktop.org/~agd5f/linux/commit/?h=drm-next-5.2-wip&id=672e78cab819ebe31e3b9b8abac367be8a110472

Alex
________________________________
From: Arnd Bergmann <arnd at arndb.de>
Sent: Thursday, March 7, 2019 5:34 AM
To: Wentland, Harry; Li, Sun peng (Leo); Deucher, Alexander; Koenig, Christian; Zhou, David(ChunMing)
Cc: Nick Desaulniers; Arnd Bergmann; David Airlie; Daniel Vetter; Koo, Anthony; Cyr, Aric; Tatla, Harmanprit; Chalmers, Kenneth; Kumarasamy, Sivapiriyan; Kees Cook; Bayan Zabihiyan; Cheng, Tony; amd-gfx at lists.freedesktop.org; dri-devel at lists.freedesktop.org; linux-kernel at vger.kernel.org
Subject: [PATCH] drm/amd/display: avoid passing enum as NULL pointer

The mod_freesync_build_vrr_infopacket() function uses rather obscure
calling conventions, where an enum is passed in through a pointer,
and a NULL pointer is expected to behave the same way as the zero-value
(TRANSFER_FUNC_UNKNOWN).

Trying to build this with clang results in a warning:

drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm.c:4601:3: error: expression which evaluates to zero treated
      as a null pointer constant of type 'const enum color_transfer_func *' [-Werror,-Wnon-literal-null-conversion]

Passing it by value instead of by reference makes the code simpler
and more conventional but should not change the behavior at all.

Fixes: c2791297013e ("drm/amd/display: Add color bit info to freesync infoframe")
Signed-off-by: Arnd Bergmann <arnd at arndb.de>
---
 drivers/gpu/drm/amd/display/modules/freesync/freesync.c | 7 +++----
 drivers/gpu/drm/amd/display/modules/inc/mod_freesync.h  | 2 +-
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/modules/freesync/freesync.c b/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
index 94a84bc57c7a..6f32fe129880 100644
--- a/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
+++ b/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
@@ -724,7 +724,7 @@ static void build_vrr_infopacket_v1(enum signal_type signal,

 static void build_vrr_infopacket_v2(enum signal_type signal,
                 const struct mod_vrr_params *vrr,
-               const enum color_transfer_func *app_tf,
+               const enum color_transfer_func app_tf,
                 struct dc_info_packet *infopacket)
 {
         unsigned int payload_size = 0;
@@ -732,8 +732,7 @@ static void build_vrr_infopacket_v2(enum signal_type signal,
         build_vrr_infopacket_header_v2(signal, infopacket, &payload_size);
         build_vrr_infopacket_data(vrr, infopacket);

-       if (app_tf != NULL)
-               build_vrr_infopacket_fs2_data(*app_tf, infopacket);
+       build_vrr_infopacket_fs2_data(app_tf, infopacket);

         build_vrr_infopacket_checksum(&payload_size, infopacket);

@@ -757,7 +756,7 @@ void mod_freesync_build_vrr_infopacket(struct mod_freesync *mod_freesync,
                 const struct dc_stream_state *stream,
                 const struct mod_vrr_params *vrr,
                 enum vrr_packet_type packet_type,
-               const enum color_transfer_func *app_tf,
+               const enum color_transfer_func app_tf,
                 struct dc_info_packet *infopacket)
 {
         /* SPD info packet for FreeSync
diff --git a/drivers/gpu/drm/amd/display/modules/inc/mod_freesync.h b/drivers/gpu/drm/amd/display/modules/inc/mod_freesync.h
index 4222e403b151..645793b924cf 100644
--- a/drivers/gpu/drm/amd/display/modules/inc/mod_freesync.h
+++ b/drivers/gpu/drm/amd/display/modules/inc/mod_freesync.h
@@ -145,7 +145,7 @@ void mod_freesync_build_vrr_infopacket(struct mod_freesync *mod_freesync,
                 const struct dc_stream_state *stream,
                 const struct mod_vrr_params *vrr,
                 enum vrr_packet_type packet_type,
-               const enum color_transfer_func *app_tf,
+               const enum color_transfer_func app_tf,
                 struct dc_info_packet *infopacket);

 void mod_freesync_build_vrr_params(struct mod_freesync *mod_freesync,
--
2.20.0

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