linux.git/include/linux/console.h, branch v5.11-rc2

Merge tag 'printk-for-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

2020-12-16T18:45:11+00:00

Pull printk updates from Petr Mladek:

 - Finally allow parallel writes and reads into/from the lockless
   ringbuffer. But it is not a complete solution. Readers are still
   serialized against each other. And nested writes are still prevented
   by printk_safe per-CPU buffers.

 - Use ttynull as the ultimate fallback for /dev/console.

 - Officially allow disabling console output by using console="" or
   console=null

 - A few code cleanups

* tag 'printk-for-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
  printk: remove logbuf_lock writer-protection of ringbuffer
  printk: inline log_output(),log_store() in vprintk_store()
  printk: remove obsolete dead assignment
  printk/console: Allow to disable console output by using console="" or console=null
  init/console: Use ttynull as a fallback when there is no console
  printk: ringbuffer: Reference text_data_ring directly in callees.

init/console: Use ttynull as a fallback when there is no console

2020-11-20T11:23:50+00:00

stdin, stdout, and stderr standard I/O stream are created for the init
process. They are not available when there is no console registered
for /dev/console. It might lead to a crash when the init process
tries to use them, see the commit 48021f98130880dd742 ("printk: handle
blank console arguments passed in.").

Normally, ttySX and ttyX consoles are used as a fallback when no consoles
are defined via the command line, device tree, or SPCR. But there
will be no console registered when an invalid console name is configured
or when the configured consoles do not exist on the system.

Users even try to avoid the console intentionally, for example,
by using console="" or console=null. It is used on production
systems where the serial port or terminal are not visible to
users. Pushing messages to these consoles would just unnecessary
slowdown the system.

Make sure that stdin, stdout, stderr, and /dev/console are always
available by a fallback to the existing ttynull driver. It has
been implemented for exactly this purpose but it was used only
when explicitly configured.

Reviewed-by: Greg Kroah-Hartman 
Reviewed-by: Guenter Roeck 
Tested-by: Guenter Roeck 
Acked-by: Sergey Senozhatsky 
Signed-off-by: Petr Mladek 
Link: https://lore.kernel.org/r/20201111135450.11214-2-pmladek@suse.com

console: Delete unused con_font_copy() callback implementations

2020-11-16T15:27:03+00:00

Recently in commit 3c4e0dff2095 ("vt: Disable KD_FONT_OP_COPY") we
disabled the KD_FONT_OP_COPY ioctl() option. Delete all the
con_font_copy() callbacks, since we no longer use them.

Mark KD_FONT_OP_COPY as "obsolete" in include/uapi/linux/kd.h, just like
what we have done for PPPIOCDETACH in commit af8d3c7c001a ("ppp: remove
the PPPIOCDETACH ioctl").

Signed-off-by: Peilin Ye 
Reviewed-by: Greg Kroah-Hartman 
Signed-off-by: Daniel Vetter 
Link: https://patchwork.freedesktop.org/patch/msgid/c8d28007edf50de4387e1532eb3eb736db716f73.1605169912.git.yepeilin.cs@gmail.com

vt: make vc_data pointers const in selection.h

2020-08-18T11:45:20+00:00

There are many functions declared in selection.h which only read from
struct vc_data passed as a parameter. Make all those uses const to hint
the compiler a bit.

Signed-off-by: Jiri Slaby 
Link: https://lore.kernel.org/r/20200818085706.12163-1-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman

vt: get rid of VT10.ID macros

2020-06-24T15:08:31+00:00

VT100ID is unused, but defined twice. Kill it.

VT102ID is used only in respond_ID. Define there a variable with proper
type and use that instead. Then drop both defines of VT102ID too.

Signed-off-by: Jiri Slaby 
Link: https://lore.kernel.org/r/20200615074910.19267-9-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman

vc: switch state to bool

2020-06-24T15:08:31+00:00

The code currently uses bitfields to store true-false values. Switch all
of that to bools. Apart from the cleanup, it saves 20B of code as many
shifts, ANDs, and ORs became simple movzb's.

Signed-off-by: Jiri Slaby 
Link: https://lore.kernel.org/r/20200615074910.19267-3-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman

vt: introduce enum vc_intensity for intensity

2020-06-24T15:08:31+00:00

Introduce names (en enum) for 0, 1, and 2 constants. We now have
VCI_HALF_BRIGHT, VCI_NORMAL, and VCI_BOLD instead.

Apart from the cleanup,
1) the enum allows for better type checking, and
2) this saves some code. No more fiddling with bits is needed in
   assembly now. (OTOH, the structure is larger.)

Signed-off-by: Jiri Slaby 
Link: https://lore.kernel.org/r/20200615074910.19267-2-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman

Merge branch 'for-5.8' into for-linus

2020-06-01T08:15:16+00:00

Merge branch 'for-5.7-console-exit' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk into tty-next

2020-03-17T14:26:43+00:00

We need the console patches in here as well for futher work from Andy.

* 'for-5.7-console-exit' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk:
  console: Introduce ->exit() callback
  console: Don't notify user space when unregister non-listed console
  console: Avoid positive return code from unregister_console()
  console: Drop misleading comment
  console: Use for_each_console() helper in unregister_console()
  console: Drop double check for console_drivers being non-NULL
  console: Don't perform test for CON_BRL flag

Signed-off-by: Greg Kroah-Hartman

printk: Correctly set CON_CONSDEV even when preferred console was not registered

2020-02-18T08:35:24+00:00

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 
[pmladek@suse.com: Correct reasoning in the commit message, comment update.]
Reviewed-by: Petr Mladek 
Reviewed-by: Sergey Senozhatsky 
Signed-off-by: Petr Mladek