Hi Rasmus, On Wed, Nov 10, 2021 at 5:51 PM Rasmus Villemoes <rasmus.villemoes@xxxxxxxxx> wrote: > On 10/11/2021 17.23, Geert Uytterhoeven wrote: > > Currently struct of_device_id is 196 (32-bit) or 200 (64-bit) bytes > > large. It contains fixed-size strings for a name, a type, and a > > compatible value, but the first two are barely used. > > OF device ID tables contain multiple entries, plus an empty sentinel > > entry. > > > > Statistics for my current kernel source tree: > > - 4487 tables with 16836 entries (3367200 bytes) > > - 176 names (average 6.7 max 23 chars) > > - 66 types (average 5.1 max 21 chars) > > - 12192 compatible values (average 18.0 max 45 chars) > > Taking into account the minimum needed size to store the strings, only > > 6.9% of the allocated space is used... > > > > Reduce kernel size by reducing the sizes of the fixed strings by one > > half. > > Tried something like this 2.5 years ago: > https://lore.kernel.org/lkml/20190425203101.9403-1-linux@xxxxxxxxxxxxxxxxxx/ I wasn't aware of that. I reworked some code which used multiple of_find_compatible_node() calls before, and noticed the end result had grown a lot due to the sheer size of of_device_id ("[PATCH] soc: renesas: Consolidate product register handling", https://lore.kernel.org/all/057721f46c7499de4133135488f0f3da7fb39265.1636570669.git.geert+renesas@xxxxxxxxx). > I think that there might be some not-in-tree code that relies on the > existing layout. I considered adding a CONFIG_ knob, either for these > sizes in particular, or more generally a def_bool y "CONFIG_LEGACY" > which embedded folks that build the entire distro from source and don't > have any legacy things can turn off, and then get more sensible defaults > all around. Most of that should have been gone since the #ifdef KERNEL was removed from include/linux/mod_devicetable.h in commit 6543becf26fff612 ("mod/file2alias: make modalias generation safe for cross compiling"). Of course you can never know for sure... Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
