[U-Boot] [PATCH 1/2] usb: kbd: allow multibyte sequences to be put into ring buffer

[Heinrich Schuchardt]

The USB keyboard driver provides a ring buffer for key strokes.

Function keys cannot be encoded as single bytes. Instead xterm control
sequences have to be put into the ring buffer.

This preparatory patch changes function usb_kbd_put_queue() to allow adding
multiple characters at once. If the buffer cannot accommodate the whole
sequence, it is rejected completely.

Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
---
 common/usb_kbd.c | 42 +++++++++++++++++++++++++-----------------
 1 file changed, 25 insertions(+), 17 deletions(-)

diff --git a/common/usb_kbd.c b/common/usb_kbd.c
index 8cbdba6ac2..706cc350a6 100644
--- a/common/usb_kbd.c
+++ b/common/usb_kbd.c
@@ -125,24 +125,32 @@ extern int __maybe_unused net_busy_flag;
 /* The period of time between two calls of usb_kbd_testc(). */
 static unsigned long __maybe_unused kbd_testc_tms;
 
-/* Puts character in the queue and sets up the in and out pointer. */
-static void usb_kbd_put_queue(struct usb_kbd_pdata *data, char c)
+/*
+ * Put characters into ring buffer.
+ *
+ * @data:	private data
+ * @buf		buffer with data to be queued
+ * @count:	number of characters to be queued
+ */
+static void usb_kbd_put_queue(struct usb_kbd_pdata *data,
+			      uint8_t *buf, int count)
 {
-	if (data->usb_in_pointer == USB_KBD_BUFFER_LEN - 1) {
-		/* Check for buffer full. */
-		if (data->usb_out_pointer == 0)
-			return;
-
-		data->usb_in_pointer = 0;
-	} else {
-		/* Check for buffer full. */
-		if (data->usb_in_pointer == data->usb_out_pointer - 1)
-			return;
-
-		data->usb_in_pointer++;
+	int i, used;
+
+	/* Check if buffer holds at least 'count' free slots */
+	used = data->usb_in_pointer - data->usb_out_pointer;
+	if (used < 0)
+		used += USB_KBD_BUFFER_LEN;
+	if (used + count >= USB_KBD_BUFFER_LEN)
+		return;
+
+	/* Copy to buffer */
+	for (i = 0; i < count; ++i) {
+		++data->usb_in_pointer;
+		if (data->usb_in_pointer == USB_KBD_BUFFER_LEN)
+			data->usb_in_pointer = 0;
+		data->usb_kbd_buffer[data->usb_in_pointer] = buf[i];
 	}
-
-	data->usb_kbd_buffer[data->usb_in_pointer] = c;
 }
 
 /*
@@ -237,7 +245,7 @@ static int usb_kbd_translate(struct usb_kbd_pdata *data, unsigned char scancode,
 	/* Report keycode if any */
 	if (keycode) {
 		debug("%c", keycode);
-		usb_kbd_put_queue(data, keycode);
+		usb_kbd_put_queue(data, &keycode, 1);
 	}
 
 	return 0;
-- 
2.14.2