drm/i915: Add fetch_and_zero() macro
A simple little macro to clear a pointer and return the old value. This
is useful for writing
value = *ptr;
if (!value)
return;
*ptr = 0;
...
free(value);
in a slightly more concise form:
value = fetch_and_zero(ptr);
if (!value)
return;
...
free(value);
with the idea that this establishes a pattern that may be extended for
atomic use (using xchg or cmpxchg) i.e. atomic_fetch_and_zero() and
similar to llist.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1471254551-25805-10-git-send-email-chris@chris-wilson.co.uk
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 25b1e6c..855833a 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3920,4 +3920,10 @@
#define ptr_pack_bits(ptr, bits) \
((typeof(ptr))((unsigned long)(ptr) | (bits)))
+#define fetch_and_zero(ptr) ({ \
+ typeof(*ptr) __T = *(ptr); \
+ *(ptr) = (typeof(*ptr))0; \
+ __T; \
+})
+
#endif