devices.txt: improve entry for comedi (char major 98)

Describe how the comedi minor device numbers are split across comedi
devices and comedi subdevices.

Replace the current, long dead URL with an official URL for the Comedi
project.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Ian Abbott 2019-09-11 17:39:41 +01:00 committed by Jonathan Corbet
parent e62be10350
commit d62e8055a5

View File

@ -1647,8 +1647,17 @@
0 = /dev/comedi0 First comedi device
1 = /dev/comedi1 Second comedi device
...
47 = /dev/comedi47 48th comedi device
See http://stm.lbl.gov/comedi.
Minors 48 to 255 are reserved for comedi subdevices with
pathnames of the form "/dev/comediX_subdY", where "X" is the
minor number of the associated comedi device and "Y" is the
subdevice number. These subdevice minors are assigned
dynamically, so there is no fixed mapping from subdevice
pathnames to minor numbers.
See http://www.comedi.org/ for information about the Comedi
project.
98 block User-mode virtual block device
0 = /dev/ubda First user-mode block device