Arnd Bergmann wrote:
> On Wednesday 17 April 2013, Linus Torvalds wrote:
>> Anyway, I'm attaching the untested patch to several drivers. Guys,
>> mind taking a look?
>
> I took a look at the hpet_mmap function, which still contains this check:
>
> if (((vma->vm_end - vma->vm_start) != PAGE_SIZE) || vma->vm_pgoff)
> return -EINVAL;
>
> As far as I can tell, this check is implied by the new code in
> vm_iomap_memory as the len argument passed here is PAGE_SIZE, so you
> can remove another three lines in hpet_mmap.
Yes indeed.
> > [...] I just have this untested patch-collection for a few random
> > drivers (picked across a few different driver subsystems, just to make
> > it interesting). I did that largely just to check the different use
> > cases, but I don't actually tend to *use* all that many fancy drivers,
> > so I don't have much of a way of testing it.
Any more-or-less recent x86 machine has HPET, so you could enable
CONFIG_HPET(_MMAP) and try the (completely untested) program below.
Regards,
Clemens
--8<---------------------------------------------------------------->8--
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/mman.h>
int main(void)
{
int fd = open("/dev/hpet", O_RDONLY);
if (fd == -1) {
perror("/dev/hpet");
return 1;
}
const volatile unsigned int *ptr = mmap(NULL, 4096, PROT_READ,
MAP_SHARED, fd, 0);
if (ptr == MAP_FAILED) {
perror("mmap");
return 1;
}
printf("frequency: %.5f MHz\n", 1e9 / ptr[1]);
for (;;) {
printf("\rcounter: %08x", ptr[60]);
fflush(stdout);
usleep(123456);
}
}
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