On Mon, Jan 04, 2010 at 06:18:08PM +0530, Maulik wrote:
>
> >>not omap-specific. How about USB: instead ?
>
> [Maulik] Yes this can go through linux-usb.
>
> > +#if defined(CONFIG_USB_NOP_XCEIV)
> > /* sometimes transceivers are accessed only through e.g. ULPI */
> > extern void usb_nop_xceiv_register(void);
> > extern void usb_nop_xceiv_unregister(void);
> > +#else
> > +extern inline void usb_nop_xceiv_register()
> > +{
> > +}
> > +
> > +extern inline void usb_nop_xceiv_unregister()
>
> >>I hope these are copy&paste error
>
> [Maulik] Nope. When 'extern' is dropped I get the following error while
> compiling when CONFIG_USB_NOP_XCEIV is NOT defined.
>
> arch/arm/plat-omap/built-in.o: In function `usb_nop_xceiv_unregister':
> /share/maulik/felipe_musb/include/linux/usb/otg.h:123: multiple definition
> of `usb_nop_xceiv_unregister'
> arch/arm/mach-omap2/built-in.o:/share/maulik/felipe_musb/include/linux/usb/o
> tg.h:123: first defined here
> arch/arm/plat-omap/built-in.o: In function `usb_nop_xceiv_register':
> /share/maulik/felipe_musb/include/linux/usb/otg.h:119: multiple definition
> of `usb_nop_xceiv_register'
> arch/arm/mach-omap2/built-in.o:/share/maulik/felipe_musb/include/linux/usb/o
> tg.h:119: first defined here
> make: *** [vmlinux.o] Error 1
>
> I referred some kernel code which uses extern inline.
>
> Any suggestions?
It needs to be static inline:
#ifdef CONFIG_USB_NO_XCEIV
/* sometimes transceivers are accessed only through e.g. ULPI */
extern void usb_nop_xceiv_register(void);
extern void usb_nop_xceiv_unregister(void);
#else
static inline void usb_nop_xceiv_register(void) { }
static inline void usb_nop_xceiv_unregister(void) { }
#endif
And you need to make sure that the actual body of the function in the
C file is encapsulated with #ifdef too, since the very point of having
it under a config option is to not include it if it's not selected
and needed.
-Olof
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