Re: [PATCH 00/14] drm/amd/pm: Replace one-element arrays with flexible-array members

[Christian König]

Am 07.10.20 um 18:01 schrieb Gustavo A. R. Silva:
> Hi all,
>
> This series aims to replace one-element arrays with flexible-array
> members.
>
> 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 flexible-array members, instead
> of one-element arrays, and use the struct_size() helper to calculate the
> size for the dynamic memory allocation.
>
> Also, save some heap space in the process. More on this on each individual
> patch.

Ah! Nice to see that finally be documented and cleaned up.

Feel free to add an Acked-by: Christian König <christian.koenig@xxxxxxx>

I also know about a case where we don't use struct_size in the DMA-buf code.

I'm the maintainer of that stuff as well, so be prepared to get patches 
thrown at you to clean that up as well.

Thanks,
Christian.

> This series also addresses multiple of the following sorts of warnings:
>
> drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/smu8_hwmgr.c:1515:37:
> warning: array subscript 1 is above array bounds of ‘const struct
> phm_clock_voltage_dependency_record[1]’ [-Warray-bounds]
>
> which, in this case, they are false positives, but nervertheless should be
> fixed in order to enable -Warray-bounds[3][4].
>
> [1] https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FFlexible_array_member&amp;data=02%7C01%7Cchristian.koenig%40amd.com%7C5312862a3b8c41838ef508d86ad969c1%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637376829947099179&amp;sdata=5LEWyR8pYSxmHsqhHiYiOS%2BPPk%2Fm5suOc6H7f5cIBL4%3D&amp;reserved=0
> [2] https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.kernel.org%2Fdoc%2Fhtml%2Fv5.9-rc1%2Fprocess%2Fdeprecated.html%23zero-length-and-one-element-arrays&amp;data=02%7C01%7Cchristian.koenig%40amd.com%7C5312862a3b8c41838ef508d86ad969c1%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637376829947099179&amp;sdata=wOqxnNkA9FnOI%2BfB3dHn9RU7cqPJ62qqGCK9gsd2i%2Bo%3D&amp;reserved=0
> [3] https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.kernel.org%2Flinus%2F44720996e2d79e47d508b0abe99b931a726a3197&amp;data=02%7C01%7Cchristian.koenig%40amd.com%7C5312862a3b8c41838ef508d86ad969c1%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637376829947099179&amp;sdata=x%2BSJeOrQA11HXoTaZEdyLyNWL9rC4GngDyoDMRBUn4M%3D&amp;reserved=0
> [4] https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2FKSPP%2Flinux%2Fissues%2F109&amp;data=02%7C01%7Cchristian.koenig%40amd.com%7C5312862a3b8c41838ef508d86ad969c1%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637376829947099179&amp;sdata=48155uVo7AboCdSZfsTP10i2rHfBJctG%2F432lD%2BpfHo%3D&amp;reserved=0
>
> Gustavo A. R. Silva (14):
>    drm/amd/pm: Replace one-element array with flexible-array member
>    drm/amd/pm: Replace one-element array with flexible-array member in
>      struct vi_dpm_table
>    drm/amd/pm: Replace one-element array with flexible-array in struct
>      phm_clock_array
>    drm/amd/pm: Replace one-element array with flexible-array in struct
>      phm_uvd_clock_voltage_dependency_table
>    drm/amd/pm: Replace one-element array with flexible-array in struct
>      phm_acp_clock_voltage_dependency_table
>    drm/amd/pm: Replace one-element array with flexible-array in struct
>      phm_phase_shedding_limits_table
>    drm/amd/pm: Replace one-element array with flexible-array in struct
>      phm_vce_clock_voltage_dependency_table
>    drm/amd/pm: Replace one-element array with flexible-array in struct
>      phm_cac_leakage_table
>    drm/amd/pm: Replace one-element array with flexible-array in struct
>      phm_samu_clock_voltage_dependency_table
>    drm/amd/pm: Replace one-element array with flexible-array in struct
>      phm_ppt_v1_clock_voltage_dependency_table
>    drm/amd/pm: Replace one-element array with flexible-array in struct
>      phm_ppt_v1_mm_clock_voltage_dependency_table
>    drm/amd/pm: Replace one-element array with flexible-array in struct
>      phm_ppt_v1_voltage_lookup_table
>    drm/amd/pm: Replace one-element array with flexible-array in struct
>      phm_ppt_v1_pcie_table
>    drm/amd/pm: Replace one-element array with flexible-array in struct
>      ATOM_Vega10_GFXCLK_Dependency_Table
>
>   drivers/gpu/drm/amd/pm/inc/hwmgr.h            | 20 ++---
>   .../drm/amd/pm/powerplay/hwmgr/hwmgr_ppt.h    |  8 +-
>   .../powerplay/hwmgr/process_pptables_v1_0.c   | 85 +++++++-----------
>   .../amd/pm/powerplay/hwmgr/processpptables.c  | 85 +++++++-----------
>   .../drm/amd/pm/powerplay/hwmgr/smu8_hwmgr.c   |  2 +-
>   .../drm/amd/pm/powerplay/hwmgr/smu_helper.c   |  5 +-
>   .../amd/pm/powerplay/hwmgr/vega10_pptable.h   |  2 +-
>   .../powerplay/hwmgr/vega10_processpptables.c  | 88 ++++++-------------
>   8 files changed, 107 insertions(+), 188 deletions(-)