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Subject[PATCH AUTOSEL 5.0 070/262] drm/amd/display: Pass app_tf by value rather than by reference
Date
From: Nathan Chancellor <natechancellor@gmail.com>

[ Upstream commit 672e78cab819ebe31e3b9b8abac367be8a110472 ]

Clang warns when an expression that equals zero is used as a null
pointer constant (in lieu of NULL):

drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm.c:4435:3:
warning: expression which evaluates to zero treated as a null pointer
constant of type 'const enum color_transfer_func *'
[-Wnon-literal-null-conversion]
TRANSFER_FUNC_UNKNOWN,
^~~~~~~~~~~~~~~~~~~~~
1 warning generated.

This warning is caused by commit bb47de736661 ("drm/amdgpu: Set FreeSync
state using drm VRR properties") and it could be solved by using NULL
instead of TRANSFER_FUNC_UNKNOWN or casting TRANSFER_FUNC_UNKNOWN as a
pointer. However, after looking into it, there doesn't appear to be a
good reason to pass app_tf by reference as it is never mutated along the
way. This is the only code path in which app_tf is used:

mod_freesync_build_vrr_infopacket ->
build_vrr_infopacket_v2 ->
build_vrr_infopacket_fs2_data

Neither mod_freesync_build_vrr_infopacket or build_vrr_infopacket_v2
modify app_tf's value and build_vrr_infopacket_fs2_data expects just
the value so we can avoid dereferencing anything by just passing in
app_tf's value to mod_freesync_build_vrr_infopacket and
build_vrr_infopacket_v2.

There is no functional change because build_vrr_infopacket_fs2_data
doesn't do anything if TRANSFER_FUNC_UNKNOWN is passed to it, the same
as not calling build_vrr_infopacket_fs2_data at all like before this
change when NULL was used for app_tf.

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 1544ed3f1747..945e845f3358 100644
--- a/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
+++ b/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
@@ -656,7 +656,7 @@ 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,
+ enum color_transfer_func app_tf,
struct dc_info_packet *infopacket)
{
unsigned int payload_size = 0;
@@ -664,8 +664,7 @@ 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);

@@ -676,7 +675,7 @@ 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,
+ 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 949a8b62aa98..063af6258fd9 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,
+ enum color_transfer_func app_tf,
struct dc_info_packet *infopacket);

void mod_freesync_build_vrr_params(struct mod_freesync *mod_freesync,
--
2.19.1
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