kernel: Relocate ring buffer suppport to 'misc' directory

Moves the source code for ring buffers to the 'misc' area, since
it isn't really a central component of the kernel. (This also
aligns the ring buffer source code with its include file, which
is already under 'include/misc'.)

Change-Id: I765a383a05f51fa67d154446f412496e689f9702
Signed-off-by: Allan Stephens <allan.stephens@windriver.com>

2 files changed, 105 insertions, 0 deletions

diff --git a/misc/Makefile b/misc/Makefile
index cb9a718d9..0072021de 100644
--- a/misc/Makefile
+++ b/misc/Makefile
@@ -3,5 +3,6 @@ obj-$(CONFIG_CPLUSPLUS) += cpp_virtual.o cpp_vtable.o               \
                            cpp_init_array.o cpp_ctors.o cpp_dtors.o
 obj-$(CONFIG_PRINTK) += printk.o
 obj-$(CONFIG_REBOOT) += reboot.o
+obj-$(CONFIG_RING_BUFFER) += ring_buffer.o
 obj-y += generated/
 obj-y += debug/
diff --git a/misc/ring_buffer.c b/misc/ring_buffer.c
new file mode 100644
index 000000000..21cdab63a
--- /dev/null
+++ b/misc/ring_buffer.c
@@ -0,0 +1,104 @@
+/* ring_buffer.c: Simple ring buffer API */
+
+/*
+ * Copyright (c) 2015 Intel Corporation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <misc/ring_buffer.h>
+
+/**
+ * Internal data structure for a buffer header.
+ *
+ * We want all of this to fit in a single uint32_t. Every item stored in the
+ * ring buffer will be one of these headers plus any extra data supplied
+ */
+struct ring_element {
+	uint32_t  type   :16; /**< Application-specific */
+	uint32_t  length :8;  /**< length in 32-bit chunks */
+	uint32_t  value  :8;  /**< Room for small integral values */
+};
+
+int sys_ring_buf_put(struct ring_buf *buf, uint16_t type, uint8_t value,
+		     uint32_t *data, uint8_t size32)
+{
+	uint32_t i, space, index, rc;
+
+	space = sys_ring_buf_space_get(buf);
+	if (space >= (size32 + 1)) {
+		struct ring_element *header =
+				(struct ring_element *)&buf->buf[buf->tail];
+		header->type = type;
+		header->length = size32;
+		header->value = value;
+
+		if (likely(buf->mask)) {
+			for (i = 0; i < size32; ++i) {
+				index = (i + buf->tail + 1) & buf->mask;
+				buf->buf[index] = data[i];
+			}
+			buf->tail = (buf->tail + size32 + 1) & buf->mask;
+		} else {
+			for (i = 0; i < size32; ++i) {
+				index = (i + buf->tail + 1) % buf->size;
+				buf->buf[index] = data[i];
+			}
+			buf->tail = (buf->tail + size32 + 1) % buf->size;
+		}
+		rc = 0;
+	} else {
+		buf->dropped_put_count++;
+		rc = -EMSGSIZE;
+	}
+
+	return rc;
+}
+
+int sys_ring_buf_get(struct ring_buf *buf, uint16_t *type, uint8_t *value,
+		     uint32_t *data, uint8_t *size32)
+{
+	struct ring_element *header;
+	uint32_t i, index;
+
+	if (sys_ring_buf_is_empty(buf)) {
+		return -EAGAIN;
+	}
+
+	header = (struct ring_element *) &buf->buf[buf->head];
+
+	if (header->length > *size32) {
+		*size32 = header->length;
+		return -EMSGSIZE;
+	}
+
+	*size32 = header->length;
+	*type = header->type;
+	*value = header->value;
+
+	if (likely(buf->mask)) {
+		for (i = 0; i < header->length; ++i) {
+			index = (i + buf->head + 1) & buf->mask;
+			data[i] = buf->buf[index];
+		}
+		buf->head = (buf->head + header->length + 1) & buf->mask;
+	} else {
+		for (i = 0; i < header->length; ++i) {
+			index = (i + buf->head + 1) % buf->size;
+			data[i] = buf->buf[index];
+		}
+		buf->head = (buf->head + header->length + 1) % buf->size;
+	}
+
+	return 0;
+}