On Friday 01 December 2006 18:21, Al Viro wrote:
> There is a tempting
> possibility to do that gradually, with all intermediates still in working
> state, provided that on all platforms currently supported by the kernel
> unsigned long and void * are indeed passed the same way (again, only for
> current kernel targets and existing gcc versions). Namely, we could
> * introduce SETUP_TIMER variant with cast to void (*)(unsigned long)
> * switch to its use, converting callback instances to take pointers
> at the same time. That would be done in reasonably sized groups.
> * once it's over, flip ->function to void (*)(void *), ->data to
> void * and update SETUP_TIMER accordingly; deal with remaining few instances
> of ->function.
Another alternative might be to define an intermediate version of
timer_list that avoids adding new macros, like
struct timer_list {
struct list_head entry;
unsigned long expires;
void (*function)(union { unsigned long l; void *p; }
__attribute__((transparent_union)));
union {
unsigned long data __deprecated;
void *obj;
};
struct tvec_t_base_s *base;
};
Unfortunately, this relies more on gcc specific behavior than we
may want, and it makes it possible to abuse in new ways, like defining
a function to take an unsigned long argument, but passing the data
as void *obj.
Arnd <><
