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. Arnd
