On Wed, Oct 7, 2015 at 1:23 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote: > On Wednesday 07 October 2015 13:04:06 Arnd Bergmann wrote: >> On Wednesday 07 October 2015 11:45:02 Russell King - ARM Linux wrote: >> > On Wed, Oct 07, 2015 at 12:41:21PM +0200, Arnd Bergmann wrote: >> > > The virtgpu driver prints the last_seq variable using the %ld or >> > > %lu format string, which does not work correctly on all architectures >> > > and causes this compiler warning on ARM: >> > > >> > > drivers/gpu/drm/virtio/virtgpu_fence.c: In function 'virtio_timeline_value_str': >> > > drivers/gpu/drm/virtio/virtgpu_fence.c:64:22: warning: format '%lu' expects argument of type 'long unsigned int', but argument 4 has type 'long long int' [-Wformat=] >> > > snprintf(str, size, "%lu", atomic64_read(&fence->drv->last_seq)); >> > > ^ >> > > drivers/gpu/drm/virtio/virtgpu_debugfs.c: In function 'virtio_gpu_debugfs_irq_info': >> > > drivers/gpu/drm/virtio/virtgpu_debugfs.c:37:16: warning: format '%ld' expects argument of type 'long int', but argument 3 has type 'long long int' [-Wformat=] >> > > seq_printf(m, "fence %ld %lld\n", >> > > ^ >> > > >> > > In order to avoid the warnings, this changes the format strings to %llu >> > > and adds a cast to u64, which makes it work the same way everywhere. >> > >> > You have to wonder why atomic64_* functions do not use u64 types. >> > If they're not reliant on manipulating 64-bit quantities, then what's >> > the point of calling them atomic _64_. >> >> I haven't checked all architectures, but I assume what happens is that >> 64-bit ones just #define atomic64_t atomic_long_t, so they don't have >> to provide three sets of functions. > > scratch that, I just looked at all the architectures and found that it's > just completely arbitrary, even within one architecture you get a mix > of 'long' and 'long long', plus this gem from MIPS: > > static __inline__ int atomic64_add_unless(atomic64_t *v, long a, long u) > > which truncates the result to 32 bit. Woops. See also my unanswered question in "atomic64 on 32-bit vs 64-bit (was: Re: Add virtio gpu driver.)", which is still valid: https://lkml.org/lkml/2015/6/28/18 Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
