---
- branch: MAIN
  date: Mon Mar 28 12:33:50 UTC 2022
  files:
  - new: '1.41'
    old: '1.40'
    path: src/sys/kern/subr_devsw.c
    pathrev: src/sys/kern/subr_devsw.c@1.41
    type: modified
  - new: '1.156'
    old: '1.155'
    path: src/sys/sys/conf.h
    pathrev: src/sys/sys/conf.h@1.156
    type: modified
  id: 20220328T123350Z.ebb60d1bd928d6c46fc30afcfbbe2f3b0a7ecb3e
  log: |
    driver(9): New devsw members d_cfdriver, d_devtounit.

    If set, then bdev_open/cdev_open will use d_devtounit to map the
    dev_t to an autoconf instance (e.g., /dev/wd0a -> wd0) and hold a
    reference with device_lookup_acquire across the call to d_open.

    This guarantees that the autoconf instance cannot be detached while
    the devsw's d_open function is trying to open it (and also that the
    autoconf instance has finished *_attach before anyone can open it).

    Of course, if the underlying hardware has gone away, there will be
    I/O errors, but this avoids software synchronization bugs between
    open and detach for drivers that opt into it.  It's up to the driver
    and bus to figure out how to deal with I/O errors from operations on
    hardware that has gone away while the software hasn't finished
    notifying everything that it's gone yet.

    XXX kernel ABI change to struct bdevsw/cdevsw requires bump
  module: src
  subject: 'CVS commit: src/sys'
  unixtime: '1648470830'
  user: riastradh