docs: console.txt: convert docs to ReST and rename to *.rst

Convert this small file to ReST in preparation for adding it to
the driver-api book.

While this is not part of the driver-api book, mark it as
:orphan:, in order to avoid build warnings.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
This commit is contained in:
Mauro Carvalho Chehab 2019-04-14 08:44:17 -03:00
parent 01c0aa7943
commit 8db8acee4b
3 changed files with 38 additions and 31 deletions

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@ -1,3 +1,6 @@
:orphan:
===============
Console Drivers
===============
@ -17,25 +20,26 @@ of driver occupying the consoles.) They can only take over the console that is
occupied by the system driver. In the same token, if the modular driver is
released by the console, the system driver will take over.
Modular drivers, from the programmer's point of view, have to call:
Modular drivers, from the programmer's point of view, have to call::
do_take_over_console() - load and bind driver to console layer
give_up_console() - unload driver; it will only work if driver
is fully unbound
In newer kernels, the following are also available:
In newer kernels, the following are also available::
do_register_con_driver()
do_unregister_con_driver()
If sysfs is enabled, the contents of /sys/class/vtconsole can be
examined. This shows the console backends currently registered by the
system which are named vtcon<n> where <n> is an integer from 0 to 15. Thus:
system which are named vtcon<n> where <n> is an integer from 0 to 15.
Thus::
ls /sys/class/vtconsole
. .. vtcon0 vtcon1
Each directory in /sys/class/vtconsole has 3 files:
Each directory in /sys/class/vtconsole has 3 files::
ls /sys/class/vtconsole/vtcon0
. .. bind name uevent
@ -46,27 +50,29 @@ What do these files signify?
read, or acts to bind or unbind the driver to the virtual consoles
when written to. The possible values are:
0 - means the driver is not bound and if echo'ed, commands the driver
0
- means the driver is not bound and if echo'ed, commands the driver
to unbind
1 - means the driver is bound and if echo'ed, commands the driver to
1
- means the driver is bound and if echo'ed, commands the driver to
bind
2. name - read-only file. Shows the name of the driver in this format:
2. name - read-only file. Shows the name of the driver in this format::
cat /sys/class/vtconsole/vtcon0/name
(S) VGA+
cat /sys/class/vtconsole/vtcon0/name
(S) VGA+
'(S)' stands for a (S)ystem driver, i.e., it cannot be directly
commanded to bind or unbind
'(S)' stands for a (S)ystem driver, i.e., it cannot be directly
commanded to bind or unbind
'VGA+' is the name of the driver
'VGA+' is the name of the driver
cat /sys/class/vtconsole/vtcon1/name
(M) frame buffer device
cat /sys/class/vtconsole/vtcon1/name
(M) frame buffer device
In this case, '(M)' stands for a (M)odular driver, one that can be
directly commanded to bind or unbind.
In this case, '(M)' stands for a (M)odular driver, one that can be
directly commanded to bind or unbind.
3. uevent - ignore this file
@ -75,14 +81,17 @@ driver takes over the consoles vacated by the driver. Binding, on the other
hand, will bind the driver to the consoles that are currently occupied by a
system driver.
NOTE1: Binding and unbinding must be selected in Kconfig. It's under:
NOTE1:
Binding and unbinding must be selected in Kconfig. It's under::
Device Drivers -> Character devices -> Support for binding and unbinding
console drivers
Device Drivers ->
Character devices ->
Support for binding and unbinding console drivers
NOTE2: If any of the virtual consoles are in KD_GRAPHICS mode, then binding or
unbinding will not succeed. An example of an application that sets the console
to KD_GRAPHICS is X.
NOTE2:
If any of the virtual consoles are in KD_GRAPHICS mode, then binding or
unbinding will not succeed. An example of an application that sets the
console to KD_GRAPHICS is X.
How useful is this feature? This is very useful for console driver
developers. By unbinding the driver from the console layer, one can unload the
@ -92,10 +101,10 @@ framebuffer console to VGA console and vice versa, this feature also makes
this possible. (NOTE NOTE NOTE: Please read fbcon.txt under Documentation/fb
for more details.)
Notes for developers:
=====================
Notes for developers
====================
do_take_over_console() is now broken up into:
do_take_over_console() is now broken up into::
do_register_con_driver()
do_bind_con_driver() - private function
@ -104,7 +113,7 @@ give_up_console() is a wrapper to do_unregister_con_driver(), and a driver must
be fully unbound for this call to succeed. con_is_bound() will check if the
driver is bound or not.
Guidelines for console driver writers:
Guidelines for console driver writers
=====================================
In order for binding to and unbinding from the console to properly work,
@ -140,6 +149,4 @@ The current crop of console drivers should still work correctly, but binding
and unbinding them may cause problems. With minimal fixes, these drivers can
be made to work correctly.
==========================
Antonino Daplas <adaplas@pol.net>

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@ -187,7 +187,7 @@ the hardware. Thus, in a VGA console::
Assuming the VGA driver can be unloaded, one must first unbind the VGA driver
from the console layer before unloading the driver. The VGA driver cannot be
unloaded if it is still bound to the console layer. (See
Documentation/console/console.txt for more information).
Documentation/console/console.rst for more information).
This is more complicated in the case of the framebuffer console (fbcon),
because fbcon is an intermediate layer between the console and the drivers::
@ -204,7 +204,7 @@ fbcon. Thus, there is no need to explicitly unbind the fbdev drivers from
fbcon.
So, how do we unbind fbcon from the console? Part of the answer is in
Documentation/console/console.txt. To summarize:
Documentation/console/console.rst. To summarize:
Echo a value to the bind file that represents the framebuffer console
driver. So assuming vtcon1 represents fbcon, then::

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@ -93,7 +93,7 @@ config VT_HW_CONSOLE_BINDING
select the console driver that will serve as the backend for the
virtual terminals.
See <file:Documentation/console/console.txt> for more
See <file:Documentation/console/console.rst> for more
information. For framebuffer console users, please refer to
<file:Documentation/fb/fbcon.rst>.