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 "warning:initializer-string-for-array-of-chars-is-too-long" 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; .init.data shrinks by another ~13K, making the whole kernel image about 83K, or 0.3%, smaller. Signed-off-by: Rasmus Villemoes <li...@rasmusvillemoes.dk> --- 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; }; -- 2.20.1