a8b5267a629f21c30d4e94ec82be193009803ddd
On Tue, Sep 21, 2004 at 07:17:34PM +0200, Kay Sievers wrote: > During the integration of HAL into the linux hotplug system, we dicover > every week a new signaling path that fails cause of the delayed > population of the sysfs files, which are connected by symlinks and > appear in something like a random order in userspace. > > It's pretty complicated to understand the connection between all these > files for all the different subsystems with all the exceptions, so most > of the users simply sleep a few seconds, but that is not acceptable for > our integration work. > > Here I try to get all the special knowledge about that behavior together > and place that in a simple binary. That program _must_ run first of all > other hotplug processsing and every later script, udev or HAL all can get > rid of the wild guesses about the right time sysfs is ready. > > It will not only wait for the "dev"-file events we handle with udev, also > for every /device-device with the corresponding bus link. > > It is provided as a patch against the current udev tree and a "install" will > place the new program in the hotplug.d directory: > > [kay@pim ~]$ tree /etc/hotplug.d/ > /etc/hotplug.d/ > `-- default > |-- 00-wait_for_sysfs.hotplug -> /sbin/wait_for_sysfs > |-- 10-udev.hotplug -> /sbin/udevsend > |-- 20-hal.hotplug -> /usr/libexec/hal.hotplug > |-- default.hotplug > `-- log.hotplug > > > For now, it logs the result of the waiting to syslog, to catch any > device, that needs special treatment. All newly discovered delay problems, > device black/whitelist updates should go into that program and we may remove > that kind of specialisation from all the other hotplug programs. > > Any patches, reports, testing is more than welcome. > > Sample debug: > Sep 21 18:44:07 localhost kernel: usb 3-2: new full speed USB device using address 12 > Sep 21 18:44:07 localhost kernel: hub 3-2:1.0: USB hub found > Sep 21 18:44:07 localhost kernel: hub 3-2:1.0: 2 ports detected > Sep 21 18:44:07 localhost 00-wait_for_sysfs.hotplug: result: waiting for sysfs successful '/devices/pci0000:00/0000:00:1d.1/usb3/3-2' > Sep 21 18:44:07 localhost 00-wait_for_sysfs.hotplug: result: waiting for sysfs successful '/devices/pci0000:00/0000:00:1d.1/usb3/3-2/3-2:1.0' > Sep 21 18:44:08 localhost kernel: usb 3-2.1: new full speed USB device using address 13 > Sep 21 18:44:08 localhost 00-wait_for_sysfs.hotplug: result: waiting for sysfs successful '/class/usb/lp0' > Sep 21 18:44:08 localhost kernel: drivers/usb/class/usblp.c: usblp0: USB Bidirectional printer dev 13 if 0 alt 1 proto 2 vid 0x067B pid 0x2305 > Sep 21 18:44:08 localhost 00-wait_for_sysfs.hotplug: result: waiting for sysfs successful '/devices/pci0000:00/0000:00:1d.1/usb3/3-2/3-2.1/3-2.1:1.0' > Sep 21 18:44:08 localhost 00-wait_for_sysfs.hotplug: result: waiting for sysfs successful '/devices/pci0000:00/0000:00:1d.1/usb3/3-2/3-2.1' > Sep 21 18:44:08 localhost udev: configured rule in '/etc/udev/rules.d/50-udev.rules' at line 29 applied, 'lp0' becomes 'usb/%k' > Sep 21 18:44:08 localhost udev: creating device node '/udev/usb/lp0' > Sep 21 18:44:09 localhost kernel: usb 3-2.2: new full speed USB device using address 14 > Sep 21 18:44:09 localhost kernel: pl2303 3-2.2:1.0: PL-2303 converter detected > Sep 21 18:44:09 localhost kernel: usb 3-2.2: PL-2303 converter now attached to ttyUSB0 > Sep 21 18:44:09 localhost 00-wait_for_sysfs.hotplug: result: waiting for sysfs successful '/devices/pci0000:00/0000:00:1d.1/usb3/3-2/3-2.2' > Sep 21 18:44:09 localhost 00-wait_for_sysfs.hotplug: result: waiting for sysfs successful '/devices/pci0000:00/0000:00:1d.1/usb3/3-2/3-2.2/3-2.2:1.0' > Sep 21 18:44:09 localhost 00-wait_for_sysfs.hotplug: result: waiting for sysfs successful '/devices/pci0000:00/0000:00:1d.1/usb3/3-2/3-2.2/3-2.2:1.0/ttyUSB0' > Sep 21 18:44:09 localhost 00-wait_for_sysfs.hotplug: result: waiting for sysfs successful '/class/tty/ttyUSB0' > Sep 21 18:44:09 localhost udev: creating device node '/udev/ttyUSB0' New version with more devices excluded from /device-link saerch and a better maching for device names.
udev - a userspace implementation of devfs
For more information on the design, and structure of this project, see the
files in the docs/ directory.
To use:
- You must be running a 2.6 version of the Linux kernel.
- Your 2.6 kernel must have had CONFIG_HOTPLUG enabled when it was built.
- Make sure sysfs is mounted. udev will figure out where sysfs is mounted, but
the traditional place for it is at /sys. You can mount it by hand by running:
mount -t sysfs none /sys
- Make sure you have the latest version of the linux-hotplug scripts. They are
available at linux-hotplug.sf.net or from your local kernel.org mirror at:
kernel.org/pub/linux/utils/kernel/hotplug/
They are required in order for udev to work properly.
If for some reason you do not install the hotplug scripts, you must tell the
kernel to point the hotplug binary at wherever you install udev at. This can
be done by:
echo "/sbin/udev" > /proc/sys/kernel/hotplug
- Build the project:
make
Note:
There are a number of different flags that you can use when building
udev. They are as follows:
prefix
set this to the default root that you want udev to be
installed into. This works just like the 'configure --prefix'
script does. Default value is ''. Only override this if you
really know what you are doing.
USE_KLIBC
if set to 'true', udev is built and linked against the
included version of klibc. Default value is 'false'.
USE_LOG
if set to 'true', udev will emit messages to the syslog when
it creates or removes device nodes. This is helpful to see
what udev is doing. This is enabled by default. Note, if you
are building udev against klibc it is recommended that you
disable this option (due to klibc's syslog implementation.)
DEBUG
if set to 'true', debugging messages will be sent to the syslog
as udev is run. Default value is 'false'.
KERNEL_DIR
If this is not set it will default to /lib/modules/`uname -r`/build
This is used if USE_KLIBC=true to find the kernel include
directory that klibc needs to build against. This must be set
if you are not building udev while running a 2.6 kernel.
So, if you want to build udev using klibc with debugging messages, you
would do:
make USE_KLIBC=true DEBUG=true
- Install the project:
make install
This will put the udev binary in /sbin, create the /udev and /etc/udev
directories, and place the udev configuration files in /etc/udev. You
will probably want to edit the namedev.* files to create custom naming
rules. More info on how the config files are set up are contained in
comments in the files, and is located in the documentation.
- Add and remove devices from the system and marvel as nodes are created
and removed in /udev/ based on the device types.
- If you later get sick of it, uninstall it:
make uninstall
Things are still quite rough, but it should work properly. If nothing
seems to happen, make sure your build worked properly by running the
udev-test.pl script as root in the test/ subdirectory of the udev source
tree.
Development and documentation help is very much appreciated, see the TODO
file for a list of things left to be done.
Any comment/questions/concerns please let me and the other udev developers
know by sending a message to the linux-hotplug-devel mailing list at:
linux-hotplug-devel@lists.sourceforge.net
greg k-h
greg@kroah.com
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