i2c: avoid dynamic stack use in dm_i2c_write
The size of the dynamic stack allocation here is bounded by the if()
statement. However, just allocating the maximum size up-front and
doing malloc() if necessary avoids code duplication (the
i2c_setup_offset() until the invocation of ->xfer), and generates much
better (smaller) code:
bloat-o-meter drivers/i2c/i2c-uclass.o.{0,1}
add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-144 (-144)
Function old new delta
dm_i2c_write 552 408 -144
Total: Before=3828, After=3684, chg -3.76%
It also makes static analysis of maximum stack usage (using the .su
files that are automatically generated during build) easier if there
are no lines saying "dynamic".
[This is not entirely equivalent to the existing code; this now uses
the stack for len <= 64 rather than len <= 63, but that seems like a
more natural limit.]
Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Reviewed-by: Heiko Schocher <hs@denx.de>
1 file changed