[PATCH][next] drm/amd/pm: Avoid multiple -Wflex-array-member-not-at-end warnings
Alex Deucher
alexdeucher at gmail.com
Wed Apr 16 15:04:04 UTC 2025
Can you resend, I can't seem to find the original emails.
Additionally, all of the NISLANDS structures are unused in amdgpu, so
those could be removed.
Alex
On Wed, Apr 16, 2025 at 12:48 AM Gustavo A. R. Silva
<gustavo at embeddedor.com> wrote:
>
> Hi all,
>
> Friendly ping (second one): who can take this patch, please? 🙂
>
> Thanks!
> -Gustavo
>
> On 11/03/25 02:10, Gustavo A. R. Silva wrote:
> > Hi all,
> >
> > Friendly ping: who can take this, please? :)
> >
> > Thanks!
> > --
> > Gustavo
> >
> > On 14/02/25 18:48, Gustavo A. R. Silva wrote:
> >> -Wflex-array-member-not-at-end was introduced in GCC-14, and we are
> >> getting ready to enable it, globally.
> >>
> >> So, in order to avoid ending up with a flexible-array member in the
> >> middle of other structs, we use the `struct_group_tagged()` helper
> >> to create a new tagged `struct NISLANDS_SMC_SWSTATE_HDR` (and `struct
> >> SISLANDS_SMC_SWSTATE_HDR`). This structures group together all the
> >> members of the flexible `struct NISLANDS_SMC_SWSTATE` (and `struct
> >> SISLANDS_SMC_SWSTATE`) except the flexible array.
> >>
> >> As a result, the array is effectively separated from the rest of the
> >> members without modifying the memory layout of the flexible structure.
> >> We then change the type of the middle struct members currently causing
> >> trouble from `struct NISLANDS_SMC_SWSTATE` to `struct
> >> NISLANDS_SMC_SWSTATE_HDR` (and from `struct SISLANDS_SMC_SWSTATE` to
> >> `struct SISLANDS_SMC_SWSTATE_HDR`).
> >>
> >> We also want to ensure that when new members need to be added to the
> >> flexible structure, they are always included within the newly created
> >> tagged struct. For this, we use `static_assert()`. This ensures that
> >> the memory layout for both the flexible structure and the new tagged
> >> struct is the same after any changes.
> >>
> >> This approach avoids having to implement `struct NISLANDS_SMC_SWSTATE_HDR`
> >> (and `struct SISLANDS_SMC_SWSTATE_HDR`) as a completely separate structure,
> >> thus preventing having to maintain two independent but basically identical
> >> structures, closing the door to potential bugs in the future.
> >>
> >> We also use `container_of()` whenever we need to retrieve a pointer to
> >> the flexible structure, through which we can access the flexible-array
> >> member, if necessary.
> >>
> >> So, with this changes, fix the following warnings:
> >>
> >> drivers/gpu/drm/amd/amdgpu/../pm/legacy-dpm/sislands_smc.h:218:49: warning: structure containing a flexible array member is not at the end of another
> >> structure [-Wflex-array-member-not-at-end]
> >> drivers/gpu/drm/amd/amdgpu/../pm/legacy-dpm/si_dpm.h:819:41: warning: structure containing a flexible array member is not at the end of another structure [-
> >> Wflex-array-member-not-at-end]
> >> drivers/gpu/drm/amd/amdgpu/../pm/legacy-dpm/si_dpm.h:818:41: warning: structure containing a flexible array member is not at the end of another structure [-
> >> Wflex-array-member-not-at-end]
> >> drivers/gpu/drm/amd/amdgpu/../pm/legacy-dpm/si_dpm.h:817:41: warning: structure containing a flexible array member is not at the end of another structure [-
> >> Wflex-array-member-not-at-end]
> >> drivers/gpu/drm/amd/amdgpu/../pm/legacy-dpm/si_dpm.h:816:41: warning: structure containing a flexible array member is not at the end of another structure [-
> >> Wflex-array-member-not-at-end]
> >>
> >> Signed-off-by: Gustavo A. R. Silva <gustavoars at kernel.org>
> >> ---
> >> drivers/gpu/drm/amd/pm/legacy-dpm/si_dpm.c | 7 ++++--
> >> drivers/gpu/drm/amd/pm/legacy-dpm/si_dpm.h | 23 +++++++++++--------
> >> .../gpu/drm/amd/pm/legacy-dpm/sislands_smc.h | 15 ++++++++----
> >> 3 files changed, 29 insertions(+), 16 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/amd/pm/legacy-dpm/si_dpm.c b/drivers/gpu/drm/amd/pm/legacy-dpm/si_dpm.c
> >> index a87dcf0974bc..2c9d473d122f 100644
> >> --- a/drivers/gpu/drm/amd/pm/legacy-dpm/si_dpm.c
> >> +++ b/drivers/gpu/drm/amd/pm/legacy-dpm/si_dpm.c
> >> @@ -5234,7 +5234,8 @@ static int si_init_smc_table(struct amdgpu_device *adev)
> >> table->driverState.flags = table->initialState.flags;
> >> table->driverState.levelCount = table->initialState.levelCount;
> >> - table->driverState.levels[0] = table->initialState.level;
> >> + container_of(&table->driverState, SISLANDS_SMC_SWSTATE, __hdr)->levels[0] =
> >> + table->initialState.level;
> >> ret = si_do_program_memory_timing_parameters(adev, amdgpu_boot_state,
> >> SISLANDS_INITIAL_STATE_ARB_INDEX);
> >> @@ -5755,7 +5756,9 @@ static int si_upload_sw_state(struct amdgpu_device *adev,
> >> int ret;
> >> u32 address = si_pi->state_table_start +
> >> offsetof(SISLANDS_SMC_STATETABLE, driverState);
> >> - SISLANDS_SMC_SWSTATE *smc_state = &si_pi->smc_statetable.driverState;
> >> + SISLANDS_SMC_SWSTATE *smc_state =
> >> + container_of(&si_pi->smc_statetable.driverState,
> >> + SISLANDS_SMC_SWSTATE, __hdr);
> >> size_t state_size = struct_size(smc_state, levels,
> >> new_state->performance_level_count);
> >> memset(smc_state, 0, state_size);
> >> diff --git a/drivers/gpu/drm/amd/pm/legacy-dpm/si_dpm.h b/drivers/gpu/drm/amd/pm/legacy-dpm/si_dpm.h
> >> index 11cb7874a6bb..62530f89ebdf 100644
> >> --- a/drivers/gpu/drm/amd/pm/legacy-dpm/si_dpm.h
> >> +++ b/drivers/gpu/drm/amd/pm/legacy-dpm/si_dpm.h
> >> @@ -784,12 +784,17 @@ typedef struct NISLANDS_SMC_HW_PERFORMANCE_LEVEL NISLANDS_SMC_HW_PERFORMANCE_LEV
> >> struct NISLANDS_SMC_SWSTATE
> >> {
> >> - uint8_t flags;
> >> - uint8_t levelCount;
> >> - uint8_t padding2;
> >> - uint8_t padding3;
> >> - NISLANDS_SMC_HW_PERFORMANCE_LEVEL levels[];
> >> + /* New members MUST be added within the struct_group() macro below. */
> >> + struct_group_tagged(NISLANDS_SMC_SWSTATE_HDR, __hdr,
> >> + uint8_t flags;
> >> + uint8_t levelCount;
> >> + uint8_t padding2;
> >> + uint8_t padding3;
> >> + );
> >> + NISLANDS_SMC_HW_PERFORMANCE_LEVEL levels[];
> >> };
> >> +static_assert(offsetof(struct NISLANDS_SMC_SWSTATE, levels) == sizeof(struct NISLANDS_SMC_SWSTATE_HDR),
> >> + "struct member likely outside of struct_group_tagged()");
> >> typedef struct NISLANDS_SMC_SWSTATE NISLANDS_SMC_SWSTATE;
> >> @@ -813,10 +818,10 @@ struct NISLANDS_SMC_STATETABLE
> >> uint32_t lowSMIO[NISLANDS_MAX_NO_VREG_STEPS];
> >> NISLANDS_SMC_VOLTAGEMASKTABLE voltageMaskTable;
> >> PP_NIslands_DPM2Parameters dpm2Params;
> >> - NISLANDS_SMC_SWSTATE initialState;
> >> - NISLANDS_SMC_SWSTATE ACPIState;
> >> - NISLANDS_SMC_SWSTATE ULVState;
> >> - NISLANDS_SMC_SWSTATE driverState;
> >> + struct NISLANDS_SMC_SWSTATE_HDR initialState;
> >> + struct NISLANDS_SMC_SWSTATE_HDR ACPIState;
> >> + struct NISLANDS_SMC_SWSTATE_HDR ULVState;
> >> + struct NISLANDS_SMC_SWSTATE_HDR driverState;
> >> NISLANDS_SMC_HW_PERFORMANCE_LEVEL dpmLevels[NISLANDS_MAX_SMC_PERFORMANCE_LEVELS_PER_SWSTATE - 1];
> >> };
> >> diff --git a/drivers/gpu/drm/amd/pm/legacy-dpm/sislands_smc.h b/drivers/gpu/drm/amd/pm/legacy-dpm/sislands_smc.h
> >> index 90ec411c5029..1711e3e35e80 100644
> >> --- a/drivers/gpu/drm/amd/pm/legacy-dpm/sislands_smc.h
> >> +++ b/drivers/gpu/drm/amd/pm/legacy-dpm/sislands_smc.h
> >> @@ -172,12 +172,17 @@ struct SISLANDS_SMC_HW_PERFORMANCE_LEVEL {
> >> typedef struct SISLANDS_SMC_HW_PERFORMANCE_LEVEL SISLANDS_SMC_HW_PERFORMANCE_LEVEL;
> >> struct SISLANDS_SMC_SWSTATE {
> >> - uint8_t flags;
> >> - uint8_t levelCount;
> >> - uint8_t padding2;
> >> - uint8_t padding3;
> >> + /* New members MUST be added within the struct_group() macro below. */
> >> + struct_group_tagged(SISLANDS_SMC_SWSTATE_HDR, __hdr,
> >> + uint8_t flags;
> >> + uint8_t levelCount;
> >> + uint8_t padding2;
> >> + uint8_t padding3;
> >> + );
> >> SISLANDS_SMC_HW_PERFORMANCE_LEVEL levels[];
> >> };
> >> +static_assert(offsetof(struct SISLANDS_SMC_SWSTATE, levels) == sizeof(struct SISLANDS_SMC_SWSTATE_HDR),
> >> + "struct member likely outside of struct_group_tagged()");
> >> typedef struct SISLANDS_SMC_SWSTATE SISLANDS_SMC_SWSTATE;
> >> @@ -215,7 +220,7 @@ struct SISLANDS_SMC_STATETABLE {
> >> struct SISLANDS_SMC_SWSTATE_SINGLE initialState;
> >> struct SISLANDS_SMC_SWSTATE_SINGLE ACPIState;
> >> struct SISLANDS_SMC_SWSTATE_SINGLE ULVState;
> >> - SISLANDS_SMC_SWSTATE driverState;
> >> + struct SISLANDS_SMC_SWSTATE_HDR driverState;
> >> SISLANDS_SMC_HW_PERFORMANCE_LEVEL dpmLevels[SISLANDS_MAX_SMC_PERFORMANCE_LEVELS_PER_SWSTATE];
> >> };
> >
>
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