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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>
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Mauro Carvalho Chehab
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8db8acee4b
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@ -1,3 +1,6 @@
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:orphan:
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===============
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Console Drivers
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===============
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@ -17,25 +20,26 @@ of driver occupying the consoles.) They can only take over the console that is
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occupied by the system driver. In the same token, if the modular driver is
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released by the console, the system driver will take over.
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Modular drivers, from the programmer's point of view, have to call:
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Modular drivers, from the programmer's point of view, have to call::
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do_take_over_console() - load and bind driver to console layer
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give_up_console() - unload driver; it will only work if driver
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is fully unbound
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In newer kernels, the following are also available:
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In newer kernels, the following are also available::
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do_register_con_driver()
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do_unregister_con_driver()
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If sysfs is enabled, the contents of /sys/class/vtconsole can be
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examined. This shows the console backends currently registered by the
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system which are named vtcon<n> where <n> is an integer from 0 to 15. Thus:
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system which are named vtcon<n> where <n> is an integer from 0 to 15.
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Thus::
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ls /sys/class/vtconsole
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. .. vtcon0 vtcon1
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Each directory in /sys/class/vtconsole has 3 files:
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Each directory in /sys/class/vtconsole has 3 files::
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ls /sys/class/vtconsole/vtcon0
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. .. bind name uevent
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@ -46,27 +50,29 @@ What do these files signify?
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read, or acts to bind or unbind the driver to the virtual consoles
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when written to. The possible values are:
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0 - means the driver is not bound and if echo'ed, commands the driver
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0
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- means the driver is not bound and if echo'ed, commands the driver
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to unbind
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1 - means the driver is bound and if echo'ed, commands the driver to
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1
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- means the driver is bound and if echo'ed, commands the driver to
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bind
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2. name - read-only file. Shows the name of the driver in this format:
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2. name - read-only file. Shows the name of the driver in this format::
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cat /sys/class/vtconsole/vtcon0/name
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(S) VGA+
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cat /sys/class/vtconsole/vtcon0/name
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(S) VGA+
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'(S)' stands for a (S)ystem driver, i.e., it cannot be directly
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commanded to bind or unbind
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'(S)' stands for a (S)ystem driver, i.e., it cannot be directly
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commanded to bind or unbind
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'VGA+' is the name of the driver
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'VGA+' is the name of the driver
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cat /sys/class/vtconsole/vtcon1/name
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(M) frame buffer device
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cat /sys/class/vtconsole/vtcon1/name
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(M) frame buffer device
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In this case, '(M)' stands for a (M)odular driver, one that can be
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directly commanded to bind or unbind.
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In this case, '(M)' stands for a (M)odular driver, one that can be
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directly commanded to bind or unbind.
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3. uevent - ignore this file
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@ -75,14 +81,17 @@ driver takes over the consoles vacated by the driver. Binding, on the other
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hand, will bind the driver to the consoles that are currently occupied by a
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system driver.
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NOTE1: Binding and unbinding must be selected in Kconfig. It's under:
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NOTE1:
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Binding and unbinding must be selected in Kconfig. It's under::
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Device Drivers -> Character devices -> Support for binding and unbinding
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console drivers
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Device Drivers ->
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Character devices ->
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Support for binding and unbinding console drivers
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NOTE2: If any of the virtual consoles are in KD_GRAPHICS mode, then binding or
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unbinding will not succeed. An example of an application that sets the console
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to KD_GRAPHICS is X.
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NOTE2:
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If any of the virtual consoles are in KD_GRAPHICS mode, then binding or
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unbinding will not succeed. An example of an application that sets the
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console to KD_GRAPHICS is X.
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How useful is this feature? This is very useful for console driver
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developers. By unbinding the driver from the console layer, one can unload the
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@ -92,10 +101,10 @@ framebuffer console to VGA console and vice versa, this feature also makes
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this possible. (NOTE NOTE NOTE: Please read fbcon.txt under Documentation/fb
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for more details.)
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Notes for developers:
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=====================
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Notes for developers
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====================
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do_take_over_console() is now broken up into:
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do_take_over_console() is now broken up into::
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do_register_con_driver()
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do_bind_con_driver() - private function
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@ -104,7 +113,7 @@ give_up_console() is a wrapper to do_unregister_con_driver(), and a driver must
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be fully unbound for this call to succeed. con_is_bound() will check if the
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driver is bound or not.
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Guidelines for console driver writers:
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Guidelines for console driver writers
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=====================================
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In order for binding to and unbinding from the console to properly work,
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@ -140,6 +149,4 @@ The current crop of console drivers should still work correctly, but binding
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and unbinding them may cause problems. With minimal fixes, these drivers can
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be made to work correctly.
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==========================
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Antonino Daplas <adaplas@pol.net>
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@ -187,7 +187,7 @@ the hardware. Thus, in a VGA console::
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Assuming the VGA driver can be unloaded, one must first unbind the VGA driver
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from the console layer before unloading the driver. The VGA driver cannot be
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unloaded if it is still bound to the console layer. (See
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Documentation/console/console.txt for more information).
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Documentation/console/console.rst for more information).
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This is more complicated in the case of the framebuffer console (fbcon),
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because fbcon is an intermediate layer between the console and the drivers::
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@ -204,7 +204,7 @@ fbcon. Thus, there is no need to explicitly unbind the fbdev drivers from
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fbcon.
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So, how do we unbind fbcon from the console? Part of the answer is in
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Documentation/console/console.txt. To summarize:
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Documentation/console/console.rst. To summarize:
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Echo a value to the bind file that represents the framebuffer console
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driver. So assuming vtcon1 represents fbcon, then::
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@ -93,7 +93,7 @@ config VT_HW_CONSOLE_BINDING
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select the console driver that will serve as the backend for the
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virtual terminals.
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See <file:Documentation/console/console.txt> for more
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See <file:Documentation/console/console.rst> for more
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information. For framebuffer console users, please refer to
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<file:Documentation/fb/fbcon.rst>.
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