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, 74 insertions, 0 deletions

diff --git a/include/cli.h b/include/cli.h
index ba5b8ebd36..c777c90313 100644
--- a/include/cli.h
+++ b/include/cli.h
@@ -7,6 +7,23 @@
 #ifndef __CLI_H
 #define __CLI_H
 
+#include <stdbool.h>
+
+/**
+ * struct cli_ch_state - state information for reading cmdline characters
+ *
+ * @esc_len: Number of escape characters read so far
+ * @esc_save: Escape characters collected so far
+ * @emit_upto: Next index to emit from esc_save
+ * @emitting: true if emitting from esc_save
+ */
+struct cli_ch_state {
+	int esc_len;
+	char esc_save[8];
+	int emit_upto;
+	bool emitting;
+};
+
 /**
  * Go into the command loop
  *
@@ -154,5 +171,62 @@ void cli_loop(void);
 void cli_init(void);
 
 #define endtick(seconds) (get_ticks() + (uint64_t)(seconds) * get_tbclk())
+#define CTL_CH(c)		((c) - 'a' + 1)
+
+/**
+ * cli_ch_init() - Set up the initial state to process input characters
+ *
+ * @cch: State to set up
+ */
+void cli_ch_init(struct cli_ch_state *cch);
+
+/**
+ * cli_ch_process() - Process an input character
+ *
+ * When @ichar is 0, this function returns any characters from an invalid escape
+ * sequence which are still pending in the buffer
+ *
+ * Otherwise it processes the input character. If it is an escape character,
+ * then an escape sequence is started and the function returns 0. If we are in
+ * the middle of an escape sequence, the character is processed and may result
+ * in returning 0 (if more characters are needed) or a valid character (if
+ * @ichar finishes the sequence).
+ *
+ * If @ichar is a valid character and there is no escape sequence in progress,
+ * then it is returned as is.
+ *
+ * If the Enter key is pressed, '\n' is returned.
+ *
+ * Usage should be like this::
+ *
+ *    struct cli_ch_state cch;
+ *
+ *    cli_ch_init(cch);
+ *    do
+ *       {
+ *       int ichar, ch;
+ *
+ *       ichar = cli_ch_process(cch, 0);
+ *       if (!ichar) {
+ *          ch = getchar();
+ *          ichar = cli_ch_process(cch, ch);
+ *       }
+ *       (handle the ichar character)
+ *    } while (!done)
+ *
+ * If tstc() is used to look for keypresses, this function can be called with
+ * @ichar set to -ETIMEDOUT if there is no character after 5-10ms. This allows
+ * the ambgiuity between the Escape key and the arrow keys (which generate an
+ * escape character followed by other characters) to be resolved.
+ *
+ * @cch: Current state
+ * @ichar: Input character to process, or 0 if none, or -ETIMEDOUT if no
+ * character has been received within a small number of milliseconds (this
+ * cancels any existing escape sequence and allows pressing the Escape key to
+ * work)
+ * Returns: Resulting input character after processing, 0 if none, '\e' if
+ * an existing escape sequence was cancelled
+ */
+int cli_ch_process(struct cli_ch_state *cch, int ichar);
 
 #endif