printk: console: Per-console loglevels

v4:

- Change base to Linus' master
- Use SRCU iterators for console walks
- Override per-console loglevels on magic sysrq
- Fix htmldocs
- Fix mistaken __user annotation in sysctl callbacks
- Consistently use indexed names (eg. ttyS0 instead of ttyS)
- Remove "The loglevel for a console can be set in many places" comment
- Remove CON_LOGLEVEL flag and infer based on >0
- Open code our dev_get_drvdata console stashing
- Split out console_effective_loglevel functions per Petr's suggestion
- Make boot_delay_msec/printk_delay check if it would be emitted
- Simplify warning on SYSLOG_ACTION_CONSOLE_LEVEL
- Save/restore ignore_per_console_loglevel on SYSLOG_ACTION_CONSOLE_{ON,OFF}
- Unify min/max level checks across sysfs/proc/syslog
- Add find_and_remove_console_option to avoid affecting io/mmio options

v3:

- Update to work with John's kthread patches
- Remove force_console_loglevel, now we only have global and local levels
- Remove minimum_console_loglevel control and document how to change it
- The minimum loglevel is now only honoured on setting global/local level
- Add ignore_per_console_loglevel
- Return -EINVAL if trying to set below minimum console level
- Add parser for named console= options
- Fix docs around ignore_loglevel: it can be changed at runtime
- Fix ordering in "in order of authority" docs
- Remove duplicated default_console_loglevel doc
- Only warn once on syslog() use

v2:

- Dynamically allocate struct device*
- Document sysfs attributes in Documentation/ABI/
- Use sysfs_emit() instead of sprintf() in dev sysfs files
- Remove WARN_ON() for device_add/IS_ERR(console_class)
- Remove "soon" comment for kernel.printk
- Fix !CONFIG_PRINTK build
- Fix device_unregister() NULL dereference if called before class setup
- Add new documentation to MAINTAINERS

Chris Down (2):
  printk: Do not delay messages which aren't solicited by any console
  printk: console: Support console-specific loglevels

 Documentation/ABI/testing/sysfs-class-console |  47 ++
 Documentation/admin-guide/index.rst           |   1 +
 .../admin-guide/kernel-parameters.txt         |  28 +-
 .../admin-guide/per-console-loglevel.rst      |  92 ++++
 Documentation/admin-guide/serial-console.rst  |  17 +-
 Documentation/core-api/printk-basics.rst      |  35 +-
 Documentation/networking/netconsole.rst       |  17 +
 MAINTAINERS                                   |   3 +
 drivers/tty/sysrq.c                           |  15 +
 include/linux/console.h                       |   3 +
 include/linux/printk.h                        |   9 +
 kernel/printk/console_cmdline.h               |   2 +
 kernel/printk/printk.c                        | 415 +++++++++++++++++-
 kernel/printk/sysctl.c                        |  57 ++-
 14 files changed, 691 insertions(+), 50 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-class-console
 create mode 100644 Documentation/admin-guide/per-console-loglevel.rst


base-commit: cb0856346a60fe3eb837ba5e73588a41f81ac05f
-- 
2.40.0