[PATCH][next] drm/radeon/si_dpm: Replace one-element array with flexible-array in struct SISLANDS_SMC_SWSTATE
From: Gustavo A. R. Silva
Date: Wed Mar 03 2021 - 14:27:34 EST
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].
Refactor the code according to the use of a flexible-array member in
struct SISLANDS_SMC_SWSTATE, instead of a one-element array, and use
the struct_size() helper to calculate the size for the allocation.
Also, this helps with the ongoing efforts to enable -Warray-bounds by
fixing the following warnings:
drivers/gpu/drm/radeon/si_dpm.c: In function ‘si_convert_power_state_to_smc’:
drivers/gpu/drm/radeon/si_dpm.c:2350:20: warning: array subscript 1 is above array bounds of ‘SISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’ {aka ‘struct SISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’} [-Warray-bounds]
2350 | smc_state->levels[i].dpm2.MaxPS = (u8)((SISLANDS_DPM2_MAX_PULSE_SKIP * (max_sclk - min_sclk)) / max_sclk);
| ~~~~~~~~~~~~~~~~~^~~
drivers/gpu/drm/radeon/si_dpm.c:2351:20: warning: array subscript 1 is above array bounds of ‘SISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’ {aka ‘struct SISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’} [-Warray-bounds]
2351 | smc_state->levels[i].dpm2.NearTDPDec = SISLANDS_DPM2_NEAR_TDP_DEC;
| ~~~~~~~~~~~~~~~~~^~~
drivers/gpu/drm/radeon/si_dpm.c:2352:20: warning: array subscript 1 is above array bounds of ‘SISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’ {aka ‘struct SISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’} [-Warray-bounds]
2352 | smc_state->levels[i].dpm2.AboveSafeInc = SISLANDS_DPM2_ABOVE_SAFE_INC;
| ~~~~~~~~~~~~~~~~~^~~
drivers/gpu/drm/radeon/si_dpm.c:2353:20: warning: array subscript 1 is above array bounds of ‘SISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’ {aka ‘struct SISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’} [-Warray-bounds]
2353 | smc_state->levels[i].dpm2.BelowSafeInc = SISLANDS_DPM2_BELOW_SAFE_INC;
| ~~~~~~~~~~~~~~~~~^~~
drivers/gpu/drm/radeon/si_dpm.c:2354:20: warning: array subscript 1 is above array bounds of ‘SISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’ {aka ‘struct SISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’} [-Warray-bounds]
2354 | smc_state->levels[i].dpm2.PwrEfficiencyRatio = cpu_to_be16(pwr_efficiency_ratio);
| ~~~~~~~~~~~~~~~~~^~~
drivers/gpu/drm/radeon/si_dpm.c:5105:20: warning: array subscript 1 is above array bounds of ‘SISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’ {aka ‘struct SISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’} [-Warray-bounds]
5105 | 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 <lkp@xxxxxxxxx>
Link: https://lore.kernel.org/lkml/603f9a8f.aDLrpMFzzSApzVYQ%25lkp@xxxxxxxxx/
Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
---
drivers/gpu/drm/radeon/si_dpm.c | 5 ++---
drivers/gpu/drm/radeon/sislands_smc.h | 10 +++++-----
2 files changed, 7 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/drm/radeon/si_dpm.c b/drivers/gpu/drm/radeon/si_dpm.c
index 91bfc4762767..918609551804 100644
--- a/drivers/gpu/drm/radeon/si_dpm.c
+++ b/drivers/gpu/drm/radeon/si_dpm.c
@@ -5250,10 +5250,9 @@ static int si_upload_sw_state(struct radeon_device *rdev,
int ret;
u32 address = si_pi->state_table_start +
offsetof(SISLANDS_SMC_STATETABLE, driverState);
- u32 state_size = sizeof(SISLANDS_SMC_SWSTATE) +
- ((new_state->performance_level_count - 1) *
- sizeof(SISLANDS_SMC_HW_PERFORMANCE_LEVEL));
SISLANDS_SMC_SWSTATE *smc_state = &si_pi->smc_statetable.driverState;
+ 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/radeon/sislands_smc.h b/drivers/gpu/drm/radeon/sislands_smc.h
index 966e3a556011..fbd6589bdab9 100644
--- a/drivers/gpu/drm/radeon/sislands_smc.h
+++ b/drivers/gpu/drm/radeon/sislands_smc.h
@@ -182,11 +182,11 @@ typedef struct SISLANDS_SMC_HW_PERFORMANCE_LEVEL SISLANDS_SMC_HW_PERFORMANCE_LEV
struct SISLANDS_SMC_SWSTATE
{
- uint8_t flags;
- uint8_t levelCount;
- uint8_t padding2;
- uint8_t padding3;
- SISLANDS_SMC_HW_PERFORMANCE_LEVEL levels[1];
+ uint8_t flags;
+ uint8_t levelCount;
+ uint8_t padding2;
+ uint8_t padding3;
+ SISLANDS_SMC_HW_PERFORMANCE_LEVEL levels[];
};
typedef struct SISLANDS_SMC_SWSTATE SISLANDS_SMC_SWSTATE;
--
2.27.0