fix [2068105] implement queueBuffer/lockBuffer/dequeueBuffer properly

Rewrote SurfaceFlinger's buffer management from the ground-up.
The design now support an arbitrary number of buffers per surface, however the current implementation is limited to four. Currently only 2 buffers are used in practice.

The main new feature is to be able to dequeue all buffers at once (very important when there are only two). 

A client can dequeue all buffers until there are none available, it can lock all buffers except the last one that is used for composition. The client will block then, until a new buffer is enqueued.

The current implementation requires that buffers are locked in the same order they are dequeued and enqueued in the same order they are locked. Only one buffer can be locked at a time.

eg. Allowed sequence:   DQ, DQ, LOCK, Q, LOCK, Q
eg. Forbidden sequence: DQ, DQ, LOCK, LOCK, Q, Q

1 files changed, 10 insertions, 1 deletions

diff --git a/libs/surfaceflinger/BufferAllocator.cpp b/libs/surfaceflinger/BufferAllocator.cpp
index cee8b64..19867a5 100644
--- a/libs/surfaceflinger/BufferAllocator.cpp
+++ b/libs/surfaceflinger/BufferAllocator.cpp
@@ -71,14 +71,23 @@ void BufferAllocator::dump(String8& result) const
     result.append(buffer);
 }
 
+static inline uint32_t clamp(uint32_t c) {
+    return c>0 ? c : 1;
+}
+
 status_t BufferAllocator::alloc(uint32_t w, uint32_t h, PixelFormat format,
         int usage, buffer_handle_t* handle, int32_t* stride)
 {
     Mutex::Autolock _l(mLock);
-    
+
+    // make sure to not allocate a 0 x 0 buffer
+    w = clamp(w);
+    h = clamp(h);
+
     // we have a h/w allocator and h/w buffer is requested
     status_t err = mAllocDev->alloc(mAllocDev,
             w, h, format, usage, handle, stride);
+
     LOGW_IF(err, "alloc(%u, %u, %d, %08x, ...) failed %d (%s)",
             w, h, format, usage, err, strerror(-err));