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vt: document vc_data by example 

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@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jiri Slaby 2016-06-23 13:34:24 +02:00 committed by Greg Kroah-Hartman
parent 1b0ec88ac1
commit a4bedd019e
1 changed files with 32 additions and 0 deletions
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32
include/linux/console_struct.h
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@ -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 */