On Sunday 06 January 2008 18:32, Carl-Daniel Hailfinger wrote:
> How do we factor out such code? I prefer macros for simple function
> wrappers and functions for multiline sequences.
As we are working with hardware we should avoid any macros for function
replacement. There are ugly side effects. Refer the getCx86()/setCx86()
disaster in the kernel for Geode-GX1 chipset programming:
What wrong with that?
#define getCx86(reg) ({ outb((reg), 0x22); inb(0x23); })
#define setCx86(reg, data) do { \
outb((reg), 0x22); \
outb((data), 0x23); \
} while (0)
This works:
x = getCx86(0x20);
x |= 0x01;
setCx86(0x20, x);
This fails badly:
setCx86(0x20, getCx86(0x20) | 0x01);
getCx86 and setCx86 defined as inline functions are working in all cases. So:
Do not use macros as functions.
Juergen
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