usb_update: add extra command "UPDATE_EXTRA_CMD_CONSOLE_READ_*"

Similar to corressponding host commands, we can read uart console buffer
by following ways:

A. Read from the beginning of buffer to the end of buffer:
  # 1. set snapshot before reading
  UPDATE_EXTRA_CMD_CONSOLE_READ_INIT
  while (true) {
    # 2. read 64 bytes back
    UPDATE_EXTRA_CMD_CONSOLE_READ_NEXT CONSOLE_READ_NEXT
    # 3. if (2) returns an empty string, break, otherwise, continue.
  }

B. Mimic `dmesg -w` (keep reading new messages)
  while (true) {
    # 1. set snapshot before reading
    UPDATE_EXTRA_CMD_CONSOLE_READ_INIT
    while (true) {
      # 2. read 64 bytes back
      UPDATE_EXTRA_CMD_CONSOLE_READ_NEXT CONSOLE_READ_RECENT
      # 3. if (2) returns an empty string, break, otherwise, continue.
    }
  }

Add argument `-l` to usb_updater2, which will perform (B).  Note that
the update interface will be occupied while `usb_updater2 -l` is still
running, so you can't use other updater command at the same time.

BRANCH=none
BUG=b:112877237
TEST=test on whiskers
Signed-off-by: Wei-Han Chen <stimim@chromium.org>

Change-Id: I8d2010f84602ca6b84034a0cabe42ae7441614e0
Reviewed-on: https://chromium-review.googlesource.com/1177293
Commit-Ready: Wei-Han Chen <stimim@chromium.org>
Tested-by: Wei-Han Chen <stimim@chromium.org>
Reviewed-by: Nicolas Boichat <drinkcat@chromium.org>

1 files changed, 32 insertions, 0 deletions

diff --git a/common/usb_update.c b/common/usb_update.c
index 0ab7a3e2c6..abf709ef61 100644
--- a/common/usb_update.c
+++ b/common/usb_update.c
@@ -16,6 +16,7 @@
 #include "rwsig.h"
 #include "sha256.h"
 #include "system.h"
+#include "uart.h"
 #include "update_fw.h"
 #include "usb-stream.h"
 #include "util.h"
@@ -352,6 +353,37 @@ static int try_vendor_command(struct consumer const *consumer, size_t count)
 			return 1;
 		}
 #endif
+#ifdef CONFIG_USB_CONSOLE_READ
+		/*
+		 * TODO(b/112877237): move this to a new interface, so we can
+		 * support reading log and other commands at the same time?
+		 */
+		case UPDATE_EXTRA_CMD_CONSOLE_READ_INIT:
+			response = uart_console_read_buffer_init();
+			break;
+		case UPDATE_EXTRA_CMD_CONSOLE_READ_NEXT: {
+			uint8_t *data = buffer + header_size;
+			uint8_t output[64];
+			uint16_t write_count = 0;
+
+			if (data_count != 1) {
+				response = EC_RES_INVALID_PARAM;
+				break;
+			}
+
+			response = uart_console_read_buffer(
+					data[0],
+					(char *)output,
+					MIN(sizeof(output),
+					    queue_space(&update_to_usb)),
+					&write_count);
+			if (response != EC_RES_SUCCESS || write_count == 0)
+				break;
+
+			QUEUE_ADD_UNITS(&update_to_usb, output, write_count);
+			return 1;
+		}
+#endif
 		default:
 			response = EC_RES_INVALID_COMMAND;
 		}