console: Add a console buffer

It is useful to be able to record console output and provide console input
via a buffer. This provides sandbox with the ability to run a command and
check its output. If the console is set to silent then no visible output
is generated.

This also provides a means to fix the problem where tests produce unwanted
output, such as errors or warnings. This can be confusing. We can instead
set the console to silent and record this output. It can be checked later
in the test if required.

It is possible that this may prove useful for non-test situations. For
example the console output may be suppressed for normal operations, but
recorded and stored for access by the OS. That feature is not implemented
at present.

Signed-off-by: Simon Glass <sjg@chromium.org>

include/asm-generic/global_data.h

@@ -21,6 +21,7 @@
  */
 
 #ifndef __ASSEMBLY__
+#include <membuff.h>
 #include <linux/list.h>
 
 typedef struct global_data {
@@ -103,6 +104,10 @@ typedef struct global_data {
 #endif
 	struct udevice *cur_serial_dev;	/* current serial device */
 	struct arch_global_data arch;	/* architecture-specific data */
+#ifdef CONFIG_CONSOLE_RECORD
+	struct membuff console_out;	/* console output */
+	struct membuff console_in;	/* console input */
+#endif
 } gd_t;
 #endif
 
@@ -121,5 +126,6 @@ typedef struct global_data {
 #define GD_FLG_FULL_MALLOC_INIT	0x00200	/* Full malloc() is ready	   */
 #define GD_FLG_SPL_INIT		0x00400	/* spl_init() has been called	   */
 #define GD_FLG_SKIP_RELOC	0x00800	/* Don't relocate */
+#define GD_FLG_RECORD		0x01000	/* Record console */
 
 #endif /* __ASM_GENERIC_GBL_DATA_H */