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From: Arnd Bergmann <arnd@arndb.de>
To: "Harry Wentland" <harry.wentland@amd.com>,
	"Leo Li" <sunpeng.li@amd.com>,
	"Alex Deucher" <alexander.deucher@amd.com>,
	"Christian König" <christian.koenig@amd.com>,
	"David (ChunMing) Zhou" <David1.Zhou@amd.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>,
	Arnd Bergmann <arnd@arndb.de>, David Airlie <airlied@linux.ie>,
	Daniel Vetter <daniel@ffwll.ch>,
	Anthony Koo <Anthony.Koo@amd.com>, Aric Cyr <Aric.Cyr@amd.com>,
	Harmanprit Tatla <Harmanprit.Tatla@amd.com>,
	Ken Chalmers <ken.chalmers@amd.com>,
	SivapiriyanKumarasamy <sivapiriyan.kumarasamy@amd.com>,
	Kees Cook <keescook@chromium.org>,
	Bayan Zabihiyan <Bayan.Zabihiyan@amd.com>,
	Tony Cheng <Tony.Cheng@amd.com>,
	amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH] drm/amd/display: avoid passing enum as NULL pointer
Date: Thu,  7 Mar 2019 11:34:29 +0100	[thread overview]
Message-ID: <20190307103454.1637485-1-arnd@arndb.de> (raw)

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@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


             reply	other threads:[~2019-03-07 10:35 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-07 10:34 Arnd Bergmann [this message]
     [not found] ` <20190307103454.1637485-1-arnd-r2nGTMty4D4@public.gmane.org>
2019-03-07 13:43   ` [PATCH] drm/amd/display: avoid passing enum as NULL pointer Deucher, Alexander
2019-03-07 15:34 ` Nathan Chancellor

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