From 4984158b95c5a0c3922cd34940c393652d080f99 Mon Sep 17 00:00:00 2001 From: Laurent Bercot Date: Sun, 14 Jan 2018 17:54:42 +0000 Subject: New mdevd model, prepare for 0.1.0.0 - mdevd-netlink removed - mdevd listens to the netlink itself - mdevd-coldplug writes nothing to stdout, but triggers the kernel to create uevents --- doc/mdevd-netlink.html | 124 ------------------------------------------------- 1 file changed, 124 deletions(-) delete mode 100644 doc/mdevd-netlink.html (limited to 'doc/mdevd-netlink.html') diff --git a/doc/mdevd-netlink.html b/doc/mdevd-netlink.html deleted file mode 100644 index d0aa054..0000000 --- a/doc/mdevd-netlink.html +++ /dev/null @@ -1,124 +0,0 @@ - - - - - - mdevd: the mdevd-netlink program - - - - - - -

-mdevd
-Software
-skarnet.org -

- -

The `mdevd-netlink` program

- -

-mdevd-netlink listens to the netlink interface for uevents -(also called "hotplug" or "udev" events), and writes those uevents to -its standard output, using a simple format. -

- -

-mdevd expects uevents in the same -format mdevd-netlink writes them. So the -mdevd-netlink | mdevd command line will function as -a daemon reading uevents from the netlink and handling them. -

- -

Interface

- -

-     mdevd-netlink [ -d notif ] [ -v verbosity ] [ -b kbufsz ]
-

- -

mdevd-netlink binds to the netlink interface and listens for -hotplug events, as the udevd program does.
It writes event information to its stdout. The output contains -null characters, so a terminal will not display them correctly. To -properly use mdevd-netlink, it should be piped into a handler -program such as mdevd.
mdevd-netlink is a long-lived program. -When it receives a SIGTERM, it stops listening to hotplug events; -it will exit as soon as it has flushed its event queue to stdout.

- -

Options

- -

-d notif : when ready (actually -listening to the netlink), write a newline to file descriptor notif -then close it. This allows mdevd-netlink to use the -s6 mechanism to -notify readiness. notif cannot be lesser than 3. If this -option is not given, no readiness notification is sent.
-v verbosity : be more or less verbose. -Default verbosity is 1. 0 will only print fatal error messages, 3 will -print warnings every time the netlink interface sends something -unexpected.
-b kbufsz : try and reserve a kernel buffer of -kbufsz bytes for the netlink queue. Too large a buffer wastes kernel memory; -too small a buffer risks losing events. The default is 65536 (which is on -the large side).

- -

Protocol

- -

An event is a series of null-terminated strings as they are sent by -the kernel to the netlink; mdevd-netlink adds a final empty string -(i.e. an additional null character) to mark the end of the series.
The first string is a short description of the event; it normally -contains the string "@/". Other strings after the first are of the form -"VARIABLE=value", and describe the environment which a hotplug helper -for the event (registered in /proc/sys/kernel/hotplug) would be -spawned with.

Example (newlines added for clarity):

-add@/class/input/input9/mouse2\0
-ACTION=add\0
-DEVPATH=/class/input/input9/mouse2\0
-SUBSYSTEM=input\0
-SEQNUM=106\0
-PHYSDEVPATH=/devices/pci0000:00/0000:00:1d.1/usb2/22/22:1.0
-PHYSDEVBUS=usb\0
-PHYSDEVDRIVER=usbhid\0
-MAJOR=13\0
-MINOR=34\0
-\0

- -

Notes

- -

mdevd-netlink is a daemon; it should be run under a proper supervision system such -as s6.
If you are running mdevd-netlink, the program you pipe its -output into should be the only program handling uevents; that means -that /proc/sys/kernel/hotplug should be empty.
The mdevd-netlink | mdevd command line is a quick -way of running a uevent manager, but there are ways to improve it: -
- Using the -execline scripting -language, the pipeline { mdevd-netlink } mdevd command -line will avoid leaving a shell around.
- The best way to use mdevd-netlink and mdevd is with a -supervision system: -under s6 or -s6-rc, write a service -pipeline where mdevd-netlink is a producer and -mdevd is a consumer. This setup has the advantage, among -others, that you can restart the netlink listener and the event handler -separately. The examples/ subdirectory of the mdevd -package contains example configurations for such a setup.

- - - -- cgit v1.3.1

The mdevd-netlink program

Interface

Options

Protocol

Notes

The `mdevd-netlink` program