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Subject[PATCH] mod_devicetable.h: reduce sizeof(struct of_device_id) by 80 bytes
A typical kernel image has hundreds of static struct of_device_id
instances (a lot of which are sentinel all-zeroes), each occupying
~200 bytes. Nobody initializes the .compatible member with strings
anywhere near 128 bytes, so a lot of that memory is simply wasted.

To verify, I first had the 0day bot chew on a patch adding a dummy
extremely long .compatible string, and I did get an email saying that
the patch resulted in lots of new
warnings. Then I had it chew on a version of this patch reducing to 46
(because gcc unfortunately does not warn when the literal sans the
terminating nul just fits), and got a SUCCESS mail listing 107
config/arch combinations.

For an arm imx_v6_v7_defconfig kernel, .rodata becomes 70K smaller; shrinks by another ~13K, making the whole kernel image
about 83K, or 0.3%, smaller.

Signed-off-by: Rasmus Villemoes <>
include/linux/mod_devicetable.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
index 448621c32e4d..502629bdac2e 100644
--- a/include/linux/mod_devicetable.h
+++ b/include/linux/mod_devicetable.h
@@ -241,7 +241,7 @@ struct sdw_device_id {
struct of_device_id {
char name[32];
char type[32];
- char compatible[128];
+ char compatible[48];
const void *data;

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