log: Add a console driver

It is useful to display log messages on the console. Add a simple driver
to handle this.

Note that this driver outputs to the console, which may be serial or
video. It does not specifically select serial output.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

common/Kconfig

@@ -474,6 +474,26 @@ config SPL_LOG_MAX_LEVEL
 	    6 - detail
 	    7 - debug
 
+config LOG_CONSOLE
+	bool "Allow log output to the console"
+	depends on LOG
+	default y
+	help
+	  Enables a log driver which writes log records to the console.
+	  Generally the console is the serial port or LCD display. Only the
+	  log message is shown - other details like level, category, file and
+	  line number are omitted.
+
+config LOG_SPL_CONSOLE
+	bool "Allow log output to the console in SPL"
+	depends on LOG_SPL
+	default y
+	help
+	  Enables a log driver which writes log records to the console.
+	  Generally the console is the serial port or LCD display. Only the
+	  log message is shown - other details like level, category, file and
+	  line number are omitted.
+
 endmenu
 
 config DEFAULT_FDT_FILE

common/Makefile

@@ -129,5 +129,6 @@ obj-$(CONFIG_FSL_DDR_INTERACTIVE) += cli_simple.o cli_readline.o
 obj-$(CONFIG_CMD_DFU) += dfu.o
 obj-y += command.o
 obj-$(CONFIG_$(SPL_)LOG) += log.o
+obj-$(CONFIG_$(SPL_)LOG_CONSOLE) += log_console.o
 obj-y += s_record.o
 obj-y += xyzModem.o

common/log_console.c

@@ -0,0 +1,23 @@
+/*
+ * Logging support
+ *
+ * Copyright (c) 2017 Google, Inc
+ * Written by Simon Glass <sjg@chromium.org>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <log.h>
+
+static int log_console_emit(struct log_device *ldev, struct log_rec *rec)
+{
+	puts(rec->msg);
+
+	return 0;
+}
+
+LOG_DRIVER(console) = {
+	.name	= "console",
+	.emit	= log_console_emit,
+};