scripts: gen_handles.py: remove size restrictions

With `gen_handles.py` now running on the first pre-built image,
`zephyr_pre0.elf` there is no requirement for the device handle arrays
to remain the same size after processing.

Remove the padding generated in `gen_handles.py`, as well as the
temporary option `CONFIG_DEVICE_HANDLE_PADDING` which was added to work
around this issue.

Signed-off-by: Jordan Yates <jordan.yates@data61.csiro.au>

include/device.h

@@ -696,51 +696,6 @@ static inline bool device_is_ready(const struct device *dev)
 	Z_DEVICE_STATE_DEFINE(node_id, dev_name, pm_action_cb)		\
 	Z_DEVICE_DEFINE_PM_SLOT(dev_name)
 
-/* Helper macros needed for CONFIG_DEVICE_HANDLE_PADDING. These should
- * be deleted when that option is removed.
- *
- * This is implemented "by hand" -- rather than using a helper macro
- * like UTIL_LISTIFY() -- because we need to allow users to wrap
- * DEVICE_DT_DEFINE with UTIL_LISTIFY, like this:
- *
- *     #define DEFINE_FOO_DEVICE(...) DEVICE_DT_DEFINE(...)
- *     UTIL_LISTIFY(N, DEFINE_FOO_DEVICE)
- *
- * If Z_DEVICE_HANDLE_PADDING uses UTIL_LISTIFY, this type of code
- * would fail, because the UTIL_LISTIFY token within the
- * Z_DEVICE_DEFINE_HANDLES expansion would not be expanded again,
- * since it appears in a context where UTIL_LISTIFY is already being
- * expanded. Standard C does not reexpand macros appearing in their
- * own expansion; this would lead to infinite recursions in general.
- */
-#define Z_DEVICE_HANDLE_PADDING \
-	Z_DEVICE_HANDLE_PADDING_(CONFIG_DEVICE_HANDLE_PADDING)
-#define Z_DEVICE_HANDLE_PADDING_(count) \
-	Z_DEVICE_HANDLE_PADDING__(count)
-#define Z_DEVICE_HANDLE_PADDING__(count) \
-	Z_DEVICE_HANDLE_PADDING_ ## count
-#define Z_DEVICE_HANDLE_PADDING_10 \
-	DEVICE_HANDLE_ENDS, Z_DEVICE_HANDLE_PADDING_9
-#define Z_DEVICE_HANDLE_PADDING_9 \
-	DEVICE_HANDLE_ENDS, Z_DEVICE_HANDLE_PADDING_8
-#define Z_DEVICE_HANDLE_PADDING_8 \
-	DEVICE_HANDLE_ENDS, Z_DEVICE_HANDLE_PADDING_7
-#define Z_DEVICE_HANDLE_PADDING_7 \
-	DEVICE_HANDLE_ENDS, Z_DEVICE_HANDLE_PADDING_6
-#define Z_DEVICE_HANDLE_PADDING_6 \
-	DEVICE_HANDLE_ENDS, Z_DEVICE_HANDLE_PADDING_5
-#define Z_DEVICE_HANDLE_PADDING_5 \
-	DEVICE_HANDLE_ENDS, Z_DEVICE_HANDLE_PADDING_4
-#define Z_DEVICE_HANDLE_PADDING_4 \
-	DEVICE_HANDLE_ENDS, Z_DEVICE_HANDLE_PADDING_3
-#define Z_DEVICE_HANDLE_PADDING_3 \
-	DEVICE_HANDLE_ENDS, Z_DEVICE_HANDLE_PADDING_2
-#define Z_DEVICE_HANDLE_PADDING_2 \
-	DEVICE_HANDLE_ENDS, Z_DEVICE_HANDLE_PADDING_1
-#define Z_DEVICE_HANDLE_PADDING_1 \
-	DEVICE_HANDLE_ENDS, Z_DEVICE_HANDLE_PADDING_0
-#define Z_DEVICE_HANDLE_PADDING_0 EMPTY
-
 /* Initial build provides a record that associates the device object
  * with its devicetree ordinal, and provides the dependency ordinals.
  * These are provided as weak definitions (to prevent the reference
@@ -776,7 +731,6 @@ BUILD_ASSERT(sizeof(device_handle_t) == 2, "fix the linker scripts");
 		))							\
 			DEVICE_HANDLE_SEP,				\
 			Z_DEVICE_EXTRA_HANDLES(__VA_ARGS__)		\
-			Z_DEVICE_HANDLE_PADDING				\
 		};
 
 #ifdef CONFIG_PM_DEVICE

kernel/Kconfig

@@ -303,22 +303,6 @@ config WAITQ_DUMB
 
 endchoice # WAITQ_ALGORITHM
 
-config DEVICE_HANDLE_PADDING
-	int "Number of additional device handles to use for padding"
-	default 0
-	range 0 10
-	help
-	  This is a "fudge factor" which works around build system
-	  limitations. It is safe to ignore unless you get a specific
-	  build system error about it.
-
-	  The option's value is the number of superfluous device handle
-	  values which are introduced into the array pointed to by each
-	  device's 'handles' member during the first linker pass.
-
-	  Each handle uses 2 bytes, so a value of 3 would use an extra
-	  6 bytes of ROM for every device.
-
 menu "Kernel Debugging and Metrics"
 
 config INIT_STACKS

scripts/gen_handles.py

@@ -306,21 +306,8 @@ def main():
                 hdls.append(DEVICE_HANDLE_SEP)
                 hdls.extend(hs.ext_deps)
 
-            # When CONFIG_USERSPACE is enabled the pre-built elf is
+            # Terminate the array with the end symbol
-            # also used to get hashes that identify kernel objects by
-            # address. We can't allow the size of any object in the
-            # final elf to change. We also must make sure at least one
-            # DEVICE_HANDLE_ENDS is inserted.
-            padding = len(hs.handles) - len(hdls)
-            assert padding > 0, \
-                (f"device {dev.sym.name}: "
-                 "linker pass 1 left no room to insert DEVICE_HANDLE_ENDS. "
-                 "To work around, increase CONFIG_DEVICE_HANDLE_PADDING by " +
-                 str(1 + (-padding)))
-            while padding > 0:
             hdls.append(DEVICE_HANDLE_ENDS)
-                padding -= 1
-            assert len(hdls) == len(hs.handles), "%s handle overflow" % (dev.sym.name,)
 
             lines = [
                 '',