Re: [PATCH ath-next] ath9k: eeprom: alias vpdTableI onto vpdTableL to shrink stack frame

[Rosen Penev]

On Thu Jun 18, 2026 at 2:51 AM PDT, Toke Høiland-Jørgensen wrote:
> Rosen Penev <rosenp@xxxxxxxxx> writes:
>
>> vpdTableL, vpdTableR, and vpdTableI are never live simultaneously.
>> vpdTableL and vpdTableR are consumed during the frequency-interpolation
>> step that writes vpdTableI; after the if/else they are never read
>> again.  Reuse vpdTableL for the interpolated result (what was
>> vpdTableI), reducing the stack frame by one 256-byte array.
>>
>> The read-via-write in the else branch is safe: ath9k_hw_interpolate()
>> receives vpdTableL[i][j] by value as a function argument before the
>> return value is written back to vpdTableL[i][j].
>>
>> Stack frame size change (x86_64, clang):
>>   before: 0x440 (1088 B)
>>   after:  0x330 (816 B)
>
> Huh? These are static variables, how is this affecting stack usage?
> I assume this is against your previous (broken) patch?
It's only broken on ARM + GCC. GCC + anything else and Clang + anything
else is fine.
>
> Anyway, adding this kind of aliasing to fix a problem that you
> introduced by changing working code with no real benefit is not an
> improvement. I'm OK with fixing actual bugs, but this is just mindless
> churn...
Fixing actual bugs is the goal yes. It makes sense to split up into
multiple parts IMO.
>
> -Toke