On Wed, Feb 10, 2021 at 6:49 PM Gustavo A. R. Silva
<gustavo...@kernel.org> wrote:
>
> There is a regular need in the kernel to provide a way to declare having
> a dynamically sized set of trailing elements in a structure. Kernel code
> should always use “flexible array members”[1] for these cases. The older
> style of one-element or zero-length arrays should no longer be used[2].
>
> Use flexible-array member in struct NISLANDS_SMC_SWSTATE, instead of
> one-element array.
>
> Also, this helps with the ongoing efforts to enable -Warray-bounds by
> fixing the following warnings:
>
> drivers/gpu/drm/radeon/ni_dpm.c: In function ‘ni_convert_power_state_to_smc’:
> drivers/gpu/drm/radeon/ni_dpm.c:2521:20: warning: array subscript 1 is above
> array bounds of ‘NISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’ {aka ‘struct
> NISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’} [-Warray-bounds]
> 2521 | smc_state->levels[i].dpm2.MaxPS =
> | ~~~~~~~~~~~~~~~~~^~~
> drivers/gpu/drm/radeon/ni_dpm.c:2523:20: warning: array subscript 1 is above
> array bounds of ‘NISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’ {aka ‘struct
> NISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’} [-Warray-bounds]
> 2523 | smc_state->levels[i].dpm2.NearTDPDec = NISLANDS_DPM2_NEAR_TDP_DEC;
> | ~~~~~~~~~~~~~~~~~^~~
> drivers/gpu/drm/radeon/ni_dpm.c:2524:20: warning: array subscript 1 is above
> array bounds of ‘NISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’ {aka ‘struct
> NISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’} [-Warray-bounds]
> 2524 | smc_state->levels[i].dpm2.AboveSafeInc =
> NISLANDS_DPM2_ABOVE_SAFE_INC;
> | ~~~~~~~~~~~~~~~~~^~~
> drivers/gpu/drm/radeon/ni_dpm.c:2525:20: warning: array subscript 1 is above
> array bounds of ‘NISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’ {aka ‘struct
> NISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’} [-Warray-bounds]
> 2525 | smc_state->levels[i].dpm2.BelowSafeInc =
> NISLANDS_DPM2_BELOW_SAFE_INC;
> | ~~~~~~~~~~~~~~~~~^~~
> drivers/gpu/drm/radeon/ni_dpm.c:2526:35: warning: array subscript 1 is above
> array bounds of ‘NISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’ {aka ‘struct
> NISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’} [-Warray-bounds]
> 2526 | smc_state->levels[i].stateFlags |=
> | ^~
> drivers/gpu/drm/radeon/ni_dpm.c:2526:35: warning: array subscript 1 is above
> array bounds of ‘NISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’ {aka ‘struct
> NISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’} [-Warray-bounds]
> 2526 | smc_state->levels[i].stateFlags |=
> | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~
> 2527 | ((i != (state->performance_level_count - 1)) && power_boost_limit)
> ?
> |
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 2528 | PPSMC_STATEFLAG_POWERBOOST : 0;
> | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/gpu/drm/radeon/ni_dpm.c:2442:20: warning: array subscript 1 is above
> array bounds of ‘NISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’ {aka ‘struct
> NISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’} [-Warray-bounds]
> 2442 | smc_state->levels[i + 1].aT = cpu_to_be32(a_t);
>
> [1] https://en.wikipedia.org/wiki/Flexible_array_member
> [2]
> https://www.kernel.org/doc/html/v5.9/process/deprecated.html#zero-length-and-one-element-arrays
>
> Link: https://github.com/KSPP/linux/issues/79
> Link: https://github.com/KSPP/linux/issues/109
> Build-tested-by: kernel test robot <l...@intel.com>
> Link: https://lore.kernel.org/lkml/6023ed54.bfiy+9uz81i6nq19%25...@intel.com/
> Signed-off-by: Gustavo A. R. Silva <gustavo...@kernel.org>
Applied. Thanks!
Alex
> ---
> drivers/gpu/drm/radeon/nislands_smc.h | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/radeon/nislands_smc.h
> b/drivers/gpu/drm/radeon/nislands_smc.h
> index 3cf8fc0d83f4..7395cb6b3cac 100644
> --- a/drivers/gpu/drm/radeon/nislands_smc.h
> +++ b/drivers/gpu/drm/radeon/nislands_smc.h
> @@ -134,11 +134,11 @@ 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[1];
> + uint8_t flags;
> + uint8_t levelCount;
> + uint8_t padding2;
> + uint8_t padding3;
> + NISLANDS_SMC_HW_PERFORMANCE_LEVEL levels[];
> };
>
> typedef struct NISLANDS_SMC_SWSTATE NISLANDS_SMC_SWSTATE;
> --
> 2.27.0
>
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