uart_buffering: expose interface to support non-host command

UART buffer could only be accessed by host command.  For detachable
devices, we don't want to enable all host commands.  Refactor and expose
an API to support accessing UART buffer directly, host command is not
necessary.

BRANCH=none
BUG=b:70482333
TEST=tested on whiskers
TEST=tested on nocturne
Signed-off-by: Wei-Han Chen <stimim@chromium.org>

Change-Id: I8a9bbad23fbd3c02df54cd7b5d59b0e8376756ac
Reviewed-on: https://chromium-review.googlesource.com/1177094
Commit-Ready: Wei-Han Chen <stimim@chromium.org>
Tested-by: Wei-Han Chen <stimim@chromium.org>
Reviewed-by: Nicolas Boichat <drinkcat@chromium.org>

2 files changed, 96 insertions, 46 deletions

diff --git a/common/uart_buffering.c b/common/uart_buffering.c
index 1f9f57f18a..7b4b864c09 100644
--- a/common/uart_buffering.c
+++ b/common/uart_buffering.c
@@ -330,6 +330,51 @@ DECLARE_HOOK(HOOK_INIT, uart_rx_dma_init, HOOK_PRIO_DEFAULT);
 
 static int host_command_console_snapshot(struct host_cmd_handler_args *args)
 {
+	return uart_console_read_buffer_init();
+}
+DECLARE_HOST_COMMAND(EC_CMD_CONSOLE_SNAPSHOT,
+		     host_command_console_snapshot,
+		     EC_VER_MASK(0));
+
+
+static int host_command_console_read(struct host_cmd_handler_args *args)
+{
+	if (args->version == 0) {
+		/*
+		 * Prior versions of this command only support reading from
+		 * an entire snapshot, not just the output since the last
+		 * snapshot.
+		 */
+		return uart_console_read_buffer(
+				CONSOLE_READ_NEXT,
+				(char *)args->response,
+				args->response_max,
+				&args->response_size);
+#ifdef CONFIG_CONSOLE_ENABLE_READ_V1
+	} else if (args->version == 1) {
+		const struct ec_params_console_read_v1 *p;
+
+		/* Check the params to figure out where to start reading. */
+		p = args->params;
+		return uart_console_read_buffer(
+				p->subcmd,
+				(char *)args->response,
+				args->response_max,
+				&args->response_size);
+#endif
+	}
+	return EC_RES_INVALID_PARAM;
+}
+DECLARE_HOST_COMMAND(EC_CMD_CONSOLE_READ,
+		     host_command_console_read,
+		     EC_VER_MASK(0)
+#ifdef CONFIG_CONSOLE_ENABLE_READ_V1
+		     | EC_VER_MASK(1)
+#endif
+		     );
+
+int uart_console_read_buffer_init(void)
+{
 	/* Assume the whole circular buffer is full */
 	tx_snapshot_head = tx_buf_head;
 	tx_snapshot_tail = TX_BUF_NEXT(tx_snapshot_head);
@@ -355,26 +400,31 @@ static int host_command_console_snapshot(struct host_cmd_handler_args *args)
 
 	return EC_RES_SUCCESS;
 }
-DECLARE_HOST_COMMAND(EC_CMD_CONSOLE_SNAPSHOT,
-		     host_command_console_snapshot,
-		     EC_VER_MASK(0));
 
-/*
- * Common code for host_command_console_read and
- * host_command_console_read_recent.
- */
-static int console_read_helper(struct host_cmd_handler_args *args,
-			       int *tail)
+int uart_console_read_buffer(uint8_t type,
+			     char *dest,
+			     uint16_t dest_size,
+			     uint16_t *write_count)
 {
-	char *dest = (char *)args->response;
+	int *tail;
+
+	switch (type) {
+	case CONSOLE_READ_NEXT:
+		tail = &tx_snapshot_tail;
+		break;
+	case CONSOLE_READ_RECENT:
+		tail = &tx_last_snapshot_head;
+		break;
+	default:
+		return EC_RES_INVALID_PARAM;
+	}
 
 	/* If no snapshot data, return empty response */
 	if (tx_snapshot_head == *tail)
 		return EC_RES_SUCCESS;
 
 	/* Copy data to response */
-	while (*tail != tx_snapshot_head &&
-	       args->response_size < args->response_max - 1) {
+	while (*tail != tx_snapshot_head && *write_count < dest_size - 1) {
 
 		/*
 		 * Copy only non-zero bytes, so that we don't copy unused
@@ -382,7 +432,7 @@ static int console_read_helper(struct host_cmd_handler_args *args,
 		 */
 		if (tx_buf[*tail]) {
 			*(dest++) = tx_buf[*tail];
-			args->response_size++;
+			(*write_count)++;
 		}
 
 		*tail = TX_BUF_NEXT(*tail);
@@ -390,39 +440,7 @@ static int console_read_helper(struct host_cmd_handler_args *args,
 
 	/* Null-terminate */
 	*(dest++) = '\0';
-	args->response_size++;
+	(*write_count)++;
 
 	return EC_RES_SUCCESS;
 }
-
-static int host_command_console_read(struct host_cmd_handler_args *args)
-{
-	if (args->version == 0) {
-		/*
-		 * Prior versions of this command only support reading from
-		 * an entire snapshot, not just the output since the last
-		 * snapshot.
-		 */
-		return console_read_helper(args, &tx_snapshot_tail);
-#ifdef CONFIG_CONSOLE_ENABLE_READ_V1
-	} else if (args->version == 1) {
-		const struct ec_params_console_read_v1 *p;
-
-		/* Check the params to figure out where to start reading. */
-		p = args->params;
-		if (p->subcmd == CONSOLE_READ_NEXT)
-			return console_read_helper(args, &tx_snapshot_tail);
-		else if (p->subcmd == CONSOLE_READ_RECENT)
-			return console_read_helper(args,
-						   &tx_last_snapshot_head);
-#endif
-	}
-	return EC_RES_INVALID_PARAM;
-}
-DECLARE_HOST_COMMAND(EC_CMD_CONSOLE_READ,
-		     host_command_console_read,
-		     EC_VER_MASK(0)
-#ifdef CONFIG_CONSOLE_ENABLE_READ_V1
-		     | EC_VER_MASK(1)
-#endif
-		     );
diff --git a/include/uart.h b/include/uart.h
index d17b161ae5..e40b0e866f 100644
--- a/include/uart.h
+++ b/include/uart.h
@@ -300,4 +300,36 @@ int uart_alt_pad_write_read(uint8_t *tx, int tx_len, uint8_t *rx, int rx_len,
  */
 void uart_default_pad_rx_interrupt(enum gpio_signal signal);
 
+/**
+ * Prepare for following `uart_console_read_buffer()` call.  It will create a
+ * snapshot of current uart buffer.
+ *
+ * @return result status (EC_RES_*)
+ */
+int uart_console_read_buffer_init(void);
+
+/**
+ * Read from uart buffer.
+ *
+ * `uart_console_read_buffer_init()` must be called first.
+ *
+ * If `type` is CONSOLE_READ_NEXT, this will return data starting from the
+ * beginning of the last snapshot created by `uart_console_read_buffer_init()`.
+ *
+ * If `type` is CONSOLE_READ_RECENT, this will start from the end of the
+ * previous snapshot (so if current snapshot and previous snapshot has overlaps,
+ * only new content will be returned).
+ *
+ * @param type		an ec_console_read_subcmd value.
+ * @param dest		output buffer, it will be a null-terminated string.
+ * @param dest_size	size of output buffer.
+ * @param write_count	number of bytes written (including '\0').
+ *
+ * @return result status (EC_RES_*)
+ */
+int uart_console_read_buffer(uint8_t type,
+			     char *dest,
+			     uint16_t dest_size,
+			     uint16_t *write_count);
+
 #endif  /* __CROS_EC_UART_H */