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device: optimize handles array

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Optimize the handles array by making the following observations:
 * The devicetree ordinal at index 0 in pass1 is discarded by
   gen_handles.py, and therefore does not appear in the pass2 array.
 * gen_handles.py does not need `DEVICE_HANDLE_ENDS` to determine the
   end of the handle array, as that information is present in the .elf.

Therefore, instead of replacing the devicetree ordinal with an
additional `DEVICE_HANDLE_ENDS` at the end (to preserve lengths), we
can simply move the ordinal to the end and have it be the original
`DEVICE_HANDLE_ENDS` symbol. This reduces the size of the array by
one handle per device (2 bytes).

Signed-off-by: Jordan Yates <jordan.yates@data61.csiro.au>
This commit is contained in:
Jordan Yates 2021-08-20 18:12:47 +10:00 • committed by Anas Nashif
commit b5c4140afb
2 changed files with 5 additions and 4 deletions
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include/device.h
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@ -702,7 +702,6 @@ BUILD_ASSERT(sizeof(device_handle_t) == 2, "fix the linker scripts");
)) \
DEVICE_HANDLE_SEP, \
Z_DEVICE_EXTRA_HANDLES(__VA_ARGS__) \
DEVICE_HANDLE_ENDS, \
};
#define Z_DEVICE_DEFINE_INIT(node_id, dev_name, pm_control_fn) \