> -Original Message-
> From: De Marchi, Lucas
> Sent: Monday, January 23, 2023 9:16 AM
> To: intel-gfx@lists.freedesktop.org; dri-de...@lists.freedesktop.org
> Cc: Srivatsa, Anusha ; Jani Nikula
> ; De Marchi, Lucas
> Subject: [PATCH v2.1] drm/i915: Add _PICK_EVEN_2RANGES()
>
> It's a constant pattern in the driver to need to use 2 ranges of MMIOs based
> on
> port, phy, pll, etc. When that happens, instead of using _PICK_EVEN(), _PICK()
> needs to be used. Using _PICK() is discouraged due to some reasons like:
>
> 1) It increases the code size since the array is declared
>in each call site
> 2) Developers need to be careful not to incur an
>out-of-bounds array access
> 3) Developers need to be careful that the indexes match the
>table. For that it may be that the table needs to contain
>holes, making (1) even worse.
>
> Add a variant of _PICK_EVEN() that works with 2 ranges and selects which one
> to use depending on the index value.
>
> v2: Fix the address expansion in the example (Anusha)
>
> Signed-off-by: Lucas De Marchi
Reviewed-by: Anusha Srivatsa
> ---
> drivers/gpu/drm/i915/i915_reg_defs.h | 28
> 1 file changed, 28 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_reg_defs.h
> b/drivers/gpu/drm/i915/i915_reg_defs.h
> index be43580a6979..bab6a9ec2ddd 100644
> --- a/drivers/gpu/drm/i915/i915_reg_defs.h
> +++ b/drivers/gpu/drm/i915/i915_reg_defs.h
> @@ -119,6 +119,34 @@
> */
> #define _PICK_EVEN(__index, __a, __b) ((__a) + (__index) * ((__b) - (__a)))
>
> +/*
> + * Like _PICK_EVEN(), but supports 2 ranges of evenly spaced address offsets.
> + * The first range is used for indexes below @__c_index, and the second
> + * range is used for anything above it. Example::
> + *
> + * #define _FOO_A0xf000
> + * #define _FOO_B0xf004
> + * #define _FOO_C0xf008
> + * #define _SUPER_FOO_A 0xa000
> + * #define _SUPER_FOO_B 0xa100
> + * #define FOO(x)_MMIO(_PICK_EVEN_RANGES(x, 3,
> \
> + * _FOO_A, _FOO_B,
> \
> + * _SUPER_FOO_A, _SUPER_FOO_B))
> + *
> + * This expands to:
> + * 0: 0xf000,
> + * 1: 0xf004,
> + * 2: 0xf008,
> + * 3: 0xa000,
> + * 4: 0xa100,
> + * 5: 0xa200,
> + * ...
> + */
> +#define _PICK_EVEN_2RANGES(__index, __c_index, __a, __b, __c, __d)
> \
> + (BUILD_BUG_ON_ZERO(!__is_constexpr(__c_index)) +
> \
> + ((__index) < (__c_index) ? _PICK_EVEN(__index, __a, __b) :
> \
> +_PICK_EVEN((__index) - (__c_index), __c,
> __d)))
> +
> /*
> * Given the arbitrary numbers in varargs, pick the 0-based __index'th
> number.
> *
> --
> 2.39.0
