On Mon, Dec 10, 2018 at 04:42:01PM -0700, Nathan Chancellor wrote:
> 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.
>
> Signed-off-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
> ---
> 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 620a171620ee..520665a9d81a 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,
> --
> 2.20.0
>
Gentle ping on this patch, it would be nice to get this fixed and into
5.1!
Thanks,
Nathan
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