Further to my question regarding weak functions versus conditional compile, I have a couple of other 'style' questions:
1) I have seen two varying applications of __attribute__ ((weak)) - The most common being of the form:
function(args) __attribute__((weak,alias("__function")));
__function(args) { /* Default functionality */ };
The other is rare (occurs only 5 times in my slightly older code base)
__attribute__((weak)) function(args) { /* Default functionality */ };
Is there any real difference between the two? Is there a reason for the second one?
2) What defines if code belongs in cpu/<cpu_type> versus lib_<cpu_type>? Reset vector and bootstrap code is fairly obvious, but I notice that serial port functionality seems to be exclusively located in cpu/<cpu_type>, interrupt handling seems to be a bit of a mix depending on the particular cpu, lib_nios2\cache.S and lib_ppc\cache.c (to me) in an odd location.
The reason I ask is that as part of my restructure of i386 / sc520, I want to make sure the right code ends up in the right place. A couple of examples: - Standard i386 interrupt handling uses 8259 PICs - This is an architectural thing, a not a hard and fast i386 cpu implementation. The sc520 has a more advanced on-chip PIC allowing up to 22 interrupts and dynamic routine of interrupt sources to interrupt priorities. - The sc520 has a some very nice on-chip timers, i386 requires external timers and/or calibrated delay loops
So I am thinking to leave all _very_ i386 CPU specific code (reset vector, bootstrap, real-to-protected mode switch, IDT, etc) in cpu/i386/ and create a new cpu/i386/sc520/ folder for _very_ sc520 specific code (memory mapped configuration register control, memory sizing). These two folders will basically have all the low level assembler code.
I was then going to move timer control, PIC setup, and serial I/O into lib_i386/ (and possible creating a sub folder lib_i386/sc520/ to hold the sc520 specific timer, PIC setup, SSI functions.
Are there any hard and fast rules I should be using to increase the chances of these changes making it into mainline more smoothly?
Regards,
Graeme