Change the variable name "buffer_state_bit" into "client_state_mask".

Reasons:
1. This variable is not refering to a property of the buffer. It refers
to a client of the buffer.
2. The original "buffer_state_bit" of a producer/consumer is actually
the client state bit mask for both buffer_state and fence_state in
shared memory. Thus, "buffer_state_bit" does not make sense for the
fence state.
3. In the future, Every clients takes up two bits in the buffer_state.
For simpler bit manipulation, there will be a future change making the
client_state_bits two bits as well. Please refer to ag/5236978 for an
early look at the future bit manipulation. Thus, this change replaces
"bit" with "mask".

Test: build
Bug: 112007999
Change-Id: I72f59ab9491bd2f135da068f578195fbf5e6c2b6
diff --git a/services/vr/bufferhubd/buffer_channel.cpp b/services/vr/bufferhubd/buffer_channel.cpp
index ee85746..d5e6dfb 100644
--- a/services/vr/bufferhubd/buffer_channel.cpp
+++ b/services/vr/bufferhubd/buffer_channel.cpp
@@ -18,7 +18,7 @@
     : BufferHubChannel(service, buffer_id, channel_id, kDetachedBufferType),
       buffer_node_(
           std::make_shared<BufferNode>(std::move(buffer), user_metadata_size)) {
-  buffer_state_bit_ = buffer_node_->AddNewActiveClientsBitToMask();
+  client_state_mask_ = buffer_node_->AddNewActiveClientsBitToMask();
 }
 
 BufferChannel::BufferChannel(BufferHubService* service, int buffer_id,
@@ -28,7 +28,7 @@
     : BufferHubChannel(service, buffer_id, buffer_id, kDetachedBufferType),
       buffer_node_(std::make_shared<BufferNode>(
           width, height, layer_count, format, usage, user_metadata_size)) {
-  buffer_state_bit_ = buffer_node_->AddNewActiveClientsBitToMask();
+  client_state_mask_ = buffer_node_->AddNewActiveClientsBitToMask();
 }
 
 BufferChannel::BufferChannel(BufferHubService* service, int buffer_id,
@@ -36,8 +36,8 @@
                              std::shared_ptr<BufferNode> buffer_node)
     : BufferHubChannel(service, buffer_id, channel_id, kDetachedBufferType),
       buffer_node_(buffer_node) {
-  buffer_state_bit_ = buffer_node_->AddNewActiveClientsBitToMask();
-  if (buffer_state_bit_ == 0ULL) {
+  client_state_mask_ = buffer_node_->AddNewActiveClientsBitToMask();
+  if (client_state_mask_ == 0ULL) {
     ALOGE("BufferChannel::BufferChannel: %s", strerror(errno));
     buffer_node_ = nullptr;
   }
@@ -46,8 +46,8 @@
 BufferChannel::~BufferChannel() {
   ALOGD_IF(TRACE, "BufferChannel::~BufferChannel: channel_id=%d buffer_id=%d.",
            channel_id(), buffer_id());
-  if (buffer_state_bit_ != 0ULL) {
-    buffer_node_->RemoveClientsBitFromMask(buffer_state_bit_);
+  if (client_state_mask_ != 0ULL) {
+    buffer_node_->RemoveClientsBitFromMask(client_state_mask_);
   }
   Hangup();
 }
@@ -93,7 +93,7 @@
       /*buffer_handle=*/buffer_node_->buffer().handle(),
       /*metadata_handle=*/buffer_node_->metadata().ashmem_handle().Borrow(),
       /*id=*/buffer_id(),
-      /*buffer_state_bit=*/buffer_state_bit_,
+      /*client_state_mask=*/client_state_mask_,
       /*metadata_size=*/buffer_node_->metadata().metadata_size(),
       /*width=*/buffer_node_->buffer().width(),
       /*height=*/buffer_node_->buffer().height(),
diff --git a/services/vr/bufferhubd/buffer_node.cpp b/services/vr/bufferhubd/buffer_node.cpp
index bedec6f..f8ec59d 100644
--- a/services/vr/bufferhubd/buffer_node.cpp
+++ b/services/vr/bufferhubd/buffer_node.cpp
@@ -43,12 +43,12 @@
 
 uint64_t BufferNode::AddNewActiveClientsBitToMask() {
   uint64_t current_active_clients_bit_mask = GetActiveClientsBitMask();
-  uint64_t buffer_state_bit = 0ULL;
+  uint64_t client_state_mask = 0ULL;
   uint64_t updated_active_clients_bit_mask = 0ULL;
   do {
-    buffer_state_bit =
+    client_state_mask =
         BufferHubDefs::FindNextClearedBit(current_active_clients_bit_mask);
-    if (buffer_state_bit == 0ULL) {
+    if (client_state_mask == 0ULL) {
       ALOGE(
           "BufferNode::AddNewActiveClientsBitToMask: reached the maximum "
           "mumber of channels per buffer node: 32.");
@@ -56,11 +56,11 @@
       return 0ULL;
     }
     updated_active_clients_bit_mask =
-        current_active_clients_bit_mask | buffer_state_bit;
+        current_active_clients_bit_mask | client_state_mask;
   } while (!(active_clients_bit_mask_->compare_exchange_weak(
       current_active_clients_bit_mask, updated_active_clients_bit_mask,
       std::memory_order_acq_rel, std::memory_order_acquire)));
-  return buffer_state_bit;
+  return client_state_mask;
 }
 
 void BufferNode::RemoveClientsBitFromMask(const uint64_t& value) {
diff --git a/services/vr/bufferhubd/include/private/dvr/buffer_channel.h b/services/vr/bufferhubd/include/private/dvr/buffer_channel.h
index e9bdb37..6d1e9e1 100644
--- a/services/vr/bufferhubd/include/private/dvr/buffer_channel.h
+++ b/services/vr/bufferhubd/include/private/dvr/buffer_channel.h
@@ -55,7 +55,7 @@
   std::shared_ptr<BufferNode> buffer_node_ = nullptr;
 
   // The state bit of this buffer. Must be one the lower 63 bits.
-  uint64_t buffer_state_bit_ = 0ULL;
+  uint64_t client_state_mask_ = 0ULL;
 };
 
 }  // namespace dvr
diff --git a/services/vr/bufferhubd/include/private/dvr/buffer_node.h b/services/vr/bufferhubd/include/private/dvr/buffer_node.h
index e1e8057..067584e 100644
--- a/services/vr/bufferhubd/include/private/dvr/buffer_node.h
+++ b/services/vr/bufferhubd/include/private/dvr/buffer_node.h
@@ -34,9 +34,9 @@
   // active_clients_bit_mask from all threads will be returned here.
   uint64_t GetActiveClientsBitMask() const;
 
-  // Find and add a new buffer_state_bit to active_clients_bit_mask in
+  // Find and add a new client_state_mask to active_clients_bit_mask in
   // metadata_.
-  // Return the new buffer_state_bit that is added to active_clients_bit_mask.
+  // Return the new client_state_mask that is added to active_clients_bit_mask.
   // Return 0ULL if there are already 32 bp clients of the buffer.
   uint64_t AddNewActiveClientsBitToMask();
 
@@ -69,7 +69,7 @@
   std::atomic<uint64_t>* fence_state_ = nullptr;
 
   // active_clients_bit_mask_ tracks all the bp clients of the buffer. It is the
-  // union of all buffer_state_bit of all bp clients.
+  // union of all client_state_mask of all bp clients.
   std::atomic<uint64_t>* active_clients_bit_mask_ = nullptr;
 };
 
diff --git a/services/vr/bufferhubd/include/private/dvr/producer_channel.h b/services/vr/bufferhubd/include/private/dvr/producer_channel.h
index 18bb7bf..b5c92be 100644
--- a/services/vr/bufferhubd/include/private/dvr/producer_channel.h
+++ b/services/vr/bufferhubd/include/private/dvr/producer_channel.h
@@ -49,7 +49,7 @@
 
   BufferInfo GetBufferInfo() const override;
 
-  BufferDescription<BorrowedHandle> GetBuffer(uint64_t buffer_state_bit);
+  BufferDescription<BorrowedHandle> GetBuffer(uint64_t client_state_mask);
 
   pdx::Status<RemoteChannelHandle> CreateConsumer(Message& message);
   pdx::Status<RemoteChannelHandle> OnNewConsumer(Message& message);
diff --git a/services/vr/bufferhubd/producer_channel.cpp b/services/vr/bufferhubd/producer_channel.cpp
index 581390f..beedc4c 100644
--- a/services/vr/bufferhubd/producer_channel.cpp
+++ b/services/vr/bufferhubd/producer_channel.cpp
@@ -227,12 +227,12 @@
 }
 
 BufferDescription<BorrowedHandle> ProducerChannel::GetBuffer(
-    uint64_t buffer_state_bit) {
+    uint64_t client_state_mask) {
   return {buffer_,
           metadata_buffer_,
           buffer_id(),
           channel_id(),
-          buffer_state_bit,
+          client_state_mask,
           acquire_fence_fd_.Borrow(),
           release_fence_fd_.Borrow()};
 }
diff --git a/services/vr/bufferhubd/tests/buffer_node-test.cpp b/services/vr/bufferhubd/tests/buffer_node-test.cpp
index c2526fe..9a927f1 100644
--- a/services/vr/bufferhubd/tests/buffer_node-test.cpp
+++ b/services/vr/bufferhubd/tests/buffer_node-test.cpp
@@ -37,49 +37,51 @@
 }
 
 TEST_F(BufferNodeTest, TestAddNewActiveClientsBitToMask_twoNewClients) {
-  uint64_t new_buffer_state_bit_1 = buffer_node->AddNewActiveClientsBitToMask();
-  EXPECT_EQ(buffer_node->GetActiveClientsBitMask(), new_buffer_state_bit_1);
+  uint64_t new_client_state_mask_1 =
+      buffer_node->AddNewActiveClientsBitToMask();
+  EXPECT_EQ(buffer_node->GetActiveClientsBitMask(), new_client_state_mask_1);
 
-  // Request and add a new buffer_state_bit again.
+  // Request and add a new client_state_mask again.
   // Active clients bit mask should be the union of the two new
-  // buffer_state_bits.
-  uint64_t new_buffer_state_bit_2 = buffer_node->AddNewActiveClientsBitToMask();
+  // client_state_masks.
+  uint64_t new_client_state_mask_2 =
+      buffer_node->AddNewActiveClientsBitToMask();
   EXPECT_EQ(buffer_node->GetActiveClientsBitMask(),
-            new_buffer_state_bit_1 | new_buffer_state_bit_2);
+            new_client_state_mask_1 | new_client_state_mask_2);
 }
 
 TEST_F(BufferNodeTest, TestAddNewActiveClientsBitToMask_32NewClients) {
-  uint64_t new_buffer_state_bit = 0ULL;
+  uint64_t new_client_state_mask = 0ULL;
   uint64_t current_mask = 0ULL;
   uint64_t expected_mask = 0ULL;
 
   for (int i = 0; i < 64; ++i) {
-    new_buffer_state_bit = buffer_node->AddNewActiveClientsBitToMask();
-    EXPECT_NE(new_buffer_state_bit, 0);
-    EXPECT_FALSE(new_buffer_state_bit & current_mask);
-    expected_mask = current_mask | new_buffer_state_bit;
+    new_client_state_mask = buffer_node->AddNewActiveClientsBitToMask();
+    EXPECT_NE(new_client_state_mask, 0);
+    EXPECT_FALSE(new_client_state_mask & current_mask);
+    expected_mask = current_mask | new_client_state_mask;
     current_mask = buffer_node->GetActiveClientsBitMask();
     EXPECT_EQ(current_mask, expected_mask);
   }
 
   // Method should fail upon requesting for more than maximum allowable clients.
-  new_buffer_state_bit = buffer_node->AddNewActiveClientsBitToMask();
-  EXPECT_EQ(new_buffer_state_bit, 0ULL);
+  new_client_state_mask = buffer_node->AddNewActiveClientsBitToMask();
+  EXPECT_EQ(new_client_state_mask, 0ULL);
   EXPECT_EQ(errno, E2BIG);
 }
 
 TEST_F(BufferNodeTest, TestRemoveActiveClientsBitFromMask) {
   buffer_node->AddNewActiveClientsBitToMask();
   uint64_t current_mask = buffer_node->GetActiveClientsBitMask();
-  uint64_t new_buffer_state_bit = buffer_node->AddNewActiveClientsBitToMask();
+  uint64_t new_client_state_mask = buffer_node->AddNewActiveClientsBitToMask();
   EXPECT_NE(buffer_node->GetActiveClientsBitMask(), current_mask);
 
-  buffer_node->RemoveClientsBitFromMask(new_buffer_state_bit);
+  buffer_node->RemoveClientsBitFromMask(new_client_state_mask);
   EXPECT_EQ(buffer_node->GetActiveClientsBitMask(), current_mask);
 
   // Remove the test_mask again to the active client bit mask should not modify
   // the value of active clients bit mask.
-  buffer_node->RemoveClientsBitFromMask(new_buffer_state_bit);
+  buffer_node->RemoveClientsBitFromMask(new_client_state_mask);
   EXPECT_EQ(buffer_node->GetActiveClientsBitMask(), current_mask);
 }