On Fri, 27 Jan 2017, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote:
> On Fri, Jan 27, 2017 at 05:57:06PM +0200, Jani Nikula wrote:
>> This allows the use of more than 3 ports/pipes/whatever without tricks,
>> even if the register offsets are not evenly spaced.
>>
>> There's the risk of out of bounds access if we're not careful; currently
>> that would "just" lead to the wrong register offset being used. It might
>> be possible to add build bug ons for build time constant indexing.
>>
>> We already have ports defined up to E, not sure if we might have bugs
>> related to them and the current _PORT3() macro.
>>
>> text data bss dec hex filename
>> 1239868 46199 4096 1290163 13afb3 drivers/gpu/drm/i915/i915.ko
>> 1238828 46199 4096 1289123 13aba3 drivers/gpu/drm/i915/i915.ko
>>
>> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
>> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
>> Cc: Tvrtko Ursulin <tursulin@xxxxxxxxxxx>
>> Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
>> ---
>> drivers/gpu/drm/i915/i915_reg.h | 11 +++++------
>> 1 file changed, 5 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
>> index 672cb102f477..c6435a447300 100644
>> --- a/drivers/gpu/drm/i915/i915_reg.h
>> +++ b/drivers/gpu/drm/i915/i915_reg.h
>> @@ -48,6 +48,8 @@ static inline bool i915_mmio_reg_valid(i915_reg_t reg)
>> return !i915_mmio_reg_equal(reg, INVALID_MMIO_REG);
>> }
>>
>> +#define _PICK(__index, ...) (((const u32 []){ __VA_ARGS__ })[__index])
>
> Very neat. The danger is that for a variable index, the compiler will
> plonk the array on the stack, for each invocation. Though for a constant
> the compiler will see through it and generate the right constant.
>
> https://godbolt.org/g/YCK1od
>
> Given that it looks like the compiler will get smarter, this looks like
> a much less error prone way of writing these.
>
> Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Thanks for the reviews, pushed to drm-intel-next-queued with Daniel's
IRC ack added on top.
BR,
Jani.
--
Jani Nikula, Intel Open Source Technology Center
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