All those members of vc_data are each explained in short. But it needs
an example for one to understand the whole picture.
So add an ascii art depicting the most important vc_data members.
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
include/linux/console_struct.h | 32 ++++++++++++++++++++++++++++++++
1 file changed, 32 insertions(+)
diff --git a/include/linux/console_struct.h b/include/linux/console_struct.h
index e329ee2667e1..5fa605c93428 100644
--- a/include/linux/console_struct.h
+++ b/include/linux/console_struct.h
@@ -21,6 +21,38 @@ struct uni_pagedir;
#define NPAR 16
+/*
+ * Example: vc_data of a console that was scrolled 3 lines down.
+ *
+ * Console buffer
+ * vc_screenbuf ---------> +----------------------+-.
+ * | initializing W | \
+ * | initializing X | |
+ * | initializing Y | > scroll-back area
+ * | initializing Z | |
+ * | | /
+ * vc_visible_origin ---> ^+----------------------+-:
+ * (changes by scroll) || Welcome to linux | \
+ * || | |
+ * vc_rows --->< | login: root | | visible on console
+ * || password: | > (vc_screenbuf_size is
+ * vc_origin -----------> || | | vc_size_row * vc_rows)
+ * (start when no scroll) || Last login: 12:28 | /
+ * v+----------------------+-:
+ * | Have a lot of fun... | \
+ * vc_pos -----------------|--------v | > scroll-front area
+ * | ~ # cat_ | /
+ * vc_scr_end -----------> +----------------------+-:
+ * (vc_origin + | | \ EMPTY, to be filled by
+ * vc_screenbuf_size) | | / vc_video_erase_char
+ * +----------------------+-'
+ * <---- 2 * vc_cols ----->
+ * <---- vc_size_row ----->
+ *
+ * Note that every character in the console buffer is accompanied with an
+ * attribute in the buffer right after the character. This is not depicted
+ * in the figure.
+ */
struct vc_data {
struct tty_port port; /* Upper level data */
--
2.9.0
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