Linux Virtualization - Oct 2015 - [PATCH] drm/virtio: use %llu format string form atomic64_t

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.

Signed-off-by: Arnd Bergmann <arnd at arndb.de>

diff --git a/drivers/gpu/drm/virtio/virtgpu_debugfs.c
b/drivers/gpu/drm/virtio/virtgpu_debugfs.c
index db8b49101a8b..512263919282 100644
--- a/drivers/gpu/drm/virtio/virtgpu_debugfs.c
+++ b/drivers/gpu/drm/virtio/virtgpu_debugfs.c
@@ -34,8 +34,8 @@ virtio_gpu_debugfs_irq_info(struct seq_file *m, void *data)
 	struct drm_info_node *node = (struct drm_info_node *) m->private;
 	struct virtio_gpu_device *vgdev = node->minor->dev->dev_private;
 
-	seq_printf(m, "fence %ld %lld\n",
-		   atomic64_read(&vgdev->fence_drv.last_seq),
+	seq_printf(m, "fence %llu %lld\n",
+		   (u64)atomic64_read(&vgdev->fence_drv.last_seq),
 		   vgdev->fence_drv.sync_seq);
 	return 0;
 }
diff --git a/drivers/gpu/drm/virtio/virtgpu_fence.c
b/drivers/gpu/drm/virtio/virtgpu_fence.c
index 1da632631dac..67097c9ce9c1 100644
--- a/drivers/gpu/drm/virtio/virtgpu_fence.c
+++ b/drivers/gpu/drm/virtio/virtgpu_fence.c
@@ -61,7 +61,7 @@ static void virtio_timeline_value_str(struct fence *f, char
*str, int size)
 {
 	struct virtio_gpu_fence *fence = to_virtio_fence(f);
 
-	snprintf(str, size, "%lu",
atomic64_read(&fence->drv->last_seq));
+	snprintf(str, size, "%llu",
(u64)atomic64_read(&fence->drv->last_seq));
 }
 
 static const struct fence_ops virtio_fence_ops = {

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_.

-- 
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according to speedtest.net.

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.

	Arnd