Merge branch '2022-01-16-bootstd-updates'

To quote the author:
So far standard boot lacks a boot menu, although it is possible to create
a rudimentary one using the existing 'bootmenu' command.

Even then, this text-based menu offer only basic functionality and does
not take full advantage of the displays which are common on many devices.

This series provides a 'bootflow menu' command which allows the user to
select from the available bootflows. An attempt is made to show the name
of the available operating systems, by reading more information into the
bootflow. A logo can be read also, where supported, so that this can be
presented to the user when an option is highlighted.

Full use is made of TrueType fonts, if enabled. For cases where only a
serial console is available, it falls back to a simple text-based menu.

All of this is implementing using a new 'expo' construct, a collection of
scenes (like menu screens) which can be navigated by the user to view
information and select options. This is fairly general and should be able
to cope with a wider array of use cases, with less hacking of the menu
code, such as is currently needed for CMD_BOOTEFI_BOOTMGR.

Of course it would be possible to enhance the existing menu rather than
creating a new setup. Instead it seems better to make the existing menu
use expo, if code space permits. It avoids the event-loop problem and
should be more extensible, given its loosely coupled components and use of
IDs instead of pointers. Further motivation is provided in the
documentation.

For now the CLI keypress-decoding code is split out to be used by the new
menu. The key codes defined by menu.h are reused also.

This is of course just a starting point. Some ideas for future work are
included in the documentation.

1 files changed, 208 insertions, 0 deletions

diff --git a/common/cli_getch.c b/common/cli_getch.c
new file mode 100644
index 00000000000..87c23edcf4b
--- /dev/null
+++ b/common/cli_getch.c
@@ -0,0 +1,208 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * (C) Copyright 2000
+ * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
+ *
+ * Copyright 2022 Google LLC
+ */
+
+#include <common.h>
+#include <cli.h>
+
+/**
+ * enum cli_esc_state_t - indicates what to do with an escape character
+ *
+ * @ESC_REJECT: Invalid escape sequence, so the esc_save[] characters are
+ *	returned from each subsequent call to cli_ch_esc()
+ * @ESC_SAVE: Character should be saved in esc_save until we have another one
+ * @ESC_CONVERTED: Escape sequence has been completed and the resulting
+ *	character is available
+ */
+enum cli_esc_state_t {
+	ESC_REJECT,
+	ESC_SAVE,
+	ESC_CONVERTED
+};
+
+void cli_ch_init(struct cli_ch_state *cch)
+{
+	memset(cch, '\0', sizeof(*cch));
+}
+
+/**
+ * cli_ch_esc() - Process a character in an ongoing escape sequence
+ *
+ * @cch: State information
+ * @ichar: Character to process
+ * @actp: Returns the action to take
+ * Returns: Output character if *actp is ESC_CONVERTED, else 0
+ */
+static int cli_ch_esc(struct cli_ch_state *cch, int ichar,
+		      enum cli_esc_state_t *actp)
+{
+	enum cli_esc_state_t act = ESC_REJECT;
+
+	switch (cch->esc_len) {
+	case 1:
+		if (ichar == '[' || ichar == 'O')
+			act = ESC_SAVE;
+		break;
+	case 2:
+		switch (ichar) {
+		case 'D':	/* <- key */
+			ichar = CTL_CH('b');
+			act = ESC_CONVERTED;
+			break;	/* pass off to ^B handler */
+		case 'C':	/* -> key */
+			ichar = CTL_CH('f');
+			act = ESC_CONVERTED;
+			break;	/* pass off to ^F handler */
+		case 'H':	/* Home key */
+			ichar = CTL_CH('a');
+			act = ESC_CONVERTED;
+			break;	/* pass off to ^A handler */
+		case 'F':	/* End key */
+			ichar = CTL_CH('e');
+			act = ESC_CONVERTED;
+			break;	/* pass off to ^E handler */
+		case 'A':	/* up arrow */
+			ichar = CTL_CH('p');
+			act = ESC_CONVERTED;
+			break;	/* pass off to ^P handler */
+		case 'B':	/* down arrow */
+			ichar = CTL_CH('n');
+			act = ESC_CONVERTED;
+			break;	/* pass off to ^N handler */
+		case '1':
+		case '2':
+		case '3':
+		case '4':
+		case '7':
+		case '8':
+			if (cch->esc_save[1] == '[') {
+				/* see if next character is ~ */
+				act = ESC_SAVE;
+			}
+			break;
+		}
+		break;
+	case 3:
+		switch (ichar) {
+		case '~':
+			switch (cch->esc_save[2]) {
+			case '3':	/* Delete key */
+				ichar = CTL_CH('d');
+				act = ESC_CONVERTED;
+				break;	/* pass to ^D handler */
+			case '1':	/* Home key */
+			case '7':
+				ichar = CTL_CH('a');
+				act = ESC_CONVERTED;
+				break;	/* pass to ^A handler */
+			case '4':	/* End key */
+			case '8':
+				ichar = CTL_CH('e');
+				act = ESC_CONVERTED;
+				break;	/* pass to ^E handler */
+			}
+			break;
+		case '0':
+			if (cch->esc_save[2] == '2')
+				act = ESC_SAVE;
+			break;
+		}
+		break;
+	case 4:
+		switch (ichar) {
+		case '0':
+		case '1':
+			act = ESC_SAVE;
+			break;		/* bracketed paste */
+		}
+		break;
+	case 5:
+		if (ichar == '~') {	/* bracketed paste */
+			ichar = 0;
+			act = ESC_CONVERTED;
+		}
+	}
+
+	*actp = act;
+
+	return act == ESC_CONVERTED ? ichar : 0;
+}
+
+int cli_ch_process(struct cli_ch_state *cch, int ichar)
+{
+	/*
+	 * ichar=0x0 when error occurs in U-Boot getchar() or when the caller
+	 * wants to check if there are more characters saved in the escape
+	 * sequence
+	 */
+	if (!ichar) {
+		if (cch->emitting) {
+			if (cch->emit_upto < cch->esc_len)
+				return cch->esc_save[cch->emit_upto++];
+			cch->emit_upto = 0;
+			cch->emitting = false;
+		}
+		return 0;
+	} else if (ichar == -ETIMEDOUT) {
+		/*
+		 * If we are in an escape sequence but nothing has followed the
+		 * Escape character, then the user probably just pressed the
+		 * Escape key. Return it and clear the sequence.
+		 */
+		if (cch->esc_len) {
+			cch->esc_len = 0;
+			return '\e';
+		}
+
+		/* Otherwise there is nothing to return */
+		return 0;
+	}
+
+	if (ichar == '\n' || ichar == '\r')
+		return '\n';
+
+	/* handle standard linux xterm esc sequences for arrow key, etc. */
+	if (cch->esc_len != 0) {
+		enum cli_esc_state_t act;
+
+		ichar = cli_ch_esc(cch, ichar, &act);
+
+		switch (act) {
+		case ESC_SAVE:
+			/* save this character and return nothing */
+			cch->esc_save[cch->esc_len++] = ichar;
+			ichar = 0;
+			break;
+		case ESC_REJECT:
+			/*
+			 * invalid escape sequence, start returning the
+			 * characters in it
+			 */
+			cch->esc_save[cch->esc_len++] = ichar;
+			ichar = cch->esc_save[cch->emit_upto++];
+			cch->emitting = true;
+			break;
+		case ESC_CONVERTED:
+			/* valid escape sequence, return the resulting char */
+			cch->esc_len = 0;
+			break;
+		}
+	}
+
+	if (ichar == '\e') {
+		if (!cch->esc_len) {
+			cch->esc_save[cch->esc_len] = ichar;
+			cch->esc_len = 1;
+		} else {
+			puts("impossible condition #876\n");
+			cch->esc_len = 0;
+		}
+		return 0;
+	}
+
+	return ichar;
+}