linux/include/linux/console.h

233 lines
7.3 KiB

[PATCH] VT binding: Add binding/unbinding support for the VT console The framebuffer console is now able to dynamically bind and unbind from the VT console layer. Due to the way the VT console layer works, the drivers themselves decide when to bind or unbind. However, it was decided that binding must be controlled, not by the drivers themselves, but by the VT console layer. With this, dynamic binding is possible for all VT console drivers, not just fbcon. Thus, the VT console layer will impose the following to all VT console drivers: - all registered VT console drivers will be entered in a private list - drivers can register themselves to the VT console layer, but they cannot decide when to bind or unbind. (Exception: To maintain backwards compatibility, take_over_console() will automatically bind the driver after registration.) - drivers can remove themselves from the list by unregistering from the VT console layer. A prerequisite for unregistration is that the driver must not be bound. The following functions are new in the vt.c: register_con_driver() - public function, this function adds the VT console driver to an internal list maintained by the VT console bind_con_driver() - private function, it binds the driver to the console take_over_console() is changed to call register_con_driver() followed by a bind_con_driver(). This is the only time drivers can decide when to bind to the VT layer. This is to maintain backwards compatibility. unbind_con_driver() - private function, it unbinds the driver from its console. The vacated consoles will be taken over by the default boot console driver. unregister_con_driver() - public function, removes the driver from the internal list maintained by the VT console. It will only succeed if the driver is currently unbound. con_is_bound() checks if the driver is currently bound or not give_up_console() is just a wrapper to unregister_con_driver(). There are also 3 additional functions meant to be called only by the tty layer for sysfs control: vt_bind() - calls bind_con_driver() vt_unbind() - calls unbind_con_driver() vt_show_drivers() - shows the list of registered drivers Most VT console drivers will continue to work as is, but might have problems when unbinding or binding which should be fixable with minimal changes. Signed-off-by: Antonino Daplas <adaplas@pol.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-26 00:27:08 -07:00
printk: Correctly set CON_CONSDEV even when preferred console was not registered CON_CONSDEV flag was historically used to put/keep the preferred console first in console_drivers list. Where the preferred console is the last on the command line. The ordering is important only when opening /dev/console: + tty_kopen() + tty_lookup_driver() + console_device() The flag was originally an implementation detail. But it was later made accessible from userspace via /proc/consoles. It was used, for example, by the tool "showconsole" to show the real tty accessible via /dev/console, see https://github.com/bitstreamout/showconsole Now, the current code sets CON_CONSDEV only for the preferred console or when a fallback console is added. The flag is not set when the preferred console is defined on the command line but it is not registered from some reasons. Simple solution is to set CON_CONSDEV flag for the first registered console. It will work most of the time because: + Most real consoles have console->device defined. + Boot consoles are removed in printk_late_init(). + unregister_console() moves CON_CONSDEV flag to the next console. Clean solution would require checking con->device when the preferred console is registered and in unregister_console(). Conclusion: Use the simple solution for now. It is better than the current state and good enough. The clean solution is not worth it. It would complicate the already complicated code without too much gain. Instead the code would deserve a complete rewrite. Link: https://lore.kernel.org/r/20200213095133.23176-4-pmladek@suse.com Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> [pmladek@suse.com: Correct reasoning in the commit message, comment update.] Reviewed-by: Petr Mladek <pmladek@suse.com> Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Petr Mladek <pmladek@suse.com>
2020-02-13 10:51:33 +01:00
printk: implement support for extended console drivers printk log_buf keeps various metadata for each message including its sequence number and timestamp. The metadata is currently available only through /dev/kmsg and stripped out before passed onto console drivers. We want this metadata to be available to console drivers too so that console consumers can get full information including the metadata and dictionary, which among other things can be used to detect whether messages got lost in transit. This patch implements support for extended console drivers. Consoles can indicate that they want extended messages by setting the new CON_EXTENDED flag and they'll be fed messages formatted the same way as /dev/kmsg. "<level>,<sequnum>,<timestamp>,<contflag>;<message text>\n" If extended consoles exist, in-kernel fragment assembly is disabled. This ensures that all messages emitted to consoles have full metadata including sequence number. The contflag carries enough information to reassemble the fragments from the reader side trivially. Note that this only affects /dev/kmsg. Regular console and /proc/kmsg outputs are not affected by this change. * Extended message formatting for console drivers is enabled iff there are registered extended consoles. * Comment describing /dev/kmsg message format updated to add missing contflag field and help distinguishing variable from verbatim terms. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: David Miller <davem@davemloft.net> Cc: Kay Sievers <kay@vrfy.org> Reviewed-by: Petr Mladek <pmladek@suse.cz> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-06-25 15:01:30 -07:00