net/mlx5: Add MLX5_ARRAY_SET64 to fix BUILD_BUG_ON

I am hitting this in mlx5:

drivers/net/ethernet/mellanox/mlx5/core/pagealloc.c: In function
reclaim_pages_cmd.clone.0:
drivers/net/ethernet/mellanox/mlx5/core/pagealloc.c:346: error: call
to __compiletime_assert_346 declared with attribute error:
BUILD_BUG_ON failed: __mlx5_bit_off(manage_pages_out, pas[i]) % 64
drivers/net/ethernet/mellanox/mlx5/core/pagealloc.c: In function give_pages:
drivers/net/ethernet/mellanox/mlx5/core/pagealloc.c:291: error: call
to __compiletime_assert_291 declared with attribute error:
BUILD_BUG_ON failed: __mlx5_bit_off(manage_pages_in, pas[i]) % 64

Problem is that this is doing a BUILD_BUG_ON on a non-constant
expression because of trying to take offset of pas[i] in the
structure.

Fix is to create MLX5_ARRAY_SET64 that takes an additional argument
that is the field index to separate between BUILD_BUG_ON on the array
constant field and the indexed field to assign the value to.
There are two callers of MLX5_SET64 that are trying to get a variable
offset, change those to call MLX5_ARRAY_SET64 passing 'pas' and 'i'
as the arguments to use in the offset check and the indexed value
assignment.

Fixes: a533ed5e179cd ("net/mlx5: Pages management commands via mlx5 ifc")
Signed-off-by: Tom Herbert <[e-mail]>
Signed-off-by: Saeed Mahameed <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/mellanox/mlx5/core/pagealloc.c

···
 
 			goto retry;
 		}
-		MLX5_SET64(manage_pages_in, in, pas[i], addr);
+		MLX5_ARRAY_SET64(manage_pages_in, in, pas, i, addr);
 	}
 
 	MLX5_SET(manage_pages_in, in, opcode, MLX5_CMD_OP_MANAGE_PAGES);
···
 		if (fwp->func_id != func_id)
 			continue;
 
-		MLX5_SET64(manage_pages_out, out, pas[i], fwp->addr);
+		MLX5_ARRAY_SET64(manage_pages_out, out, pas, i, fwp->addr);
 		i++;
 	}
 

include/linux/mlx5/device.h

···
 	___t; \
 })
 
-#define MLX5_SET64(typ, p, fld, v) do { \
+#define __MLX5_SET64(typ, p, fld, v) do { \
 	BUILD_BUG_ON(__mlx5_bit_sz(typ, fld) != 64); \
-	BUILD_BUG_ON(__mlx5_bit_off(typ, fld) % 64); \
 	*((__be64 *)(p) + __mlx5_64_off(typ, fld)) = cpu_to_be64(v); \
+} while (0)
+
+#define MLX5_SET64(typ, p, fld, v) do { \
+	BUILD_BUG_ON(__mlx5_bit_off(typ, fld) % 64); \
+	__MLX5_SET64(typ, p, fld, v); \
+} while (0)
+
+#define MLX5_ARRAY_SET64(typ, p, fld, idx, v) do { \
+	BUILD_BUG_ON(__mlx5_bit_off(typ, fld) % 64); \
+	__MLX5_SET64(typ, p, fld[idx], v); \
 } while (0)
 
 #define MLX5_GET64(typ, p, fld) be64_to_cpu(*((__be64 *)(p) + __mlx5_64_off(typ, fld)))