[PLUG] centos/rhel 7 ttyUSB group ownership with FTDI adapter

[Galen Seitz]

Hi,

When I connect a Prolific-based USB serial adapter to my CentOS 7 
machine, the corresponding ttyUSB device has dialout group ownership.

[root at toto ~]# ls -l /dev/ttyUSB*
crw-rw----. 1 root dialout 188, 0 Nov 26 14:15 /dev/ttyUSB0

However, when I connect an FTDI-based serial adapter, the device has 
root group ownership.

[root at toto ~]# ls -l /dev/ttyUSB*
crw-rw----. 1 root dialout 188, 0 Nov 26 14:15 /dev/ttyUSB0
crw-rw----+ 1 root root    188, 1 Nov 26 14:16 /dev/ttyUSB1

Note the trailing '+' on the permissions.  It appears something is 
setting up an ACL, but only for the FTDI.

[root at toto ~]# getfacl /dev/ttyUSB1
getfacl: Removing leading '/' from absolute path names
# file: dev/ttyUSB1
# owner: root
# group: root
user::rw-
user:galens:rw-
group::rw-
mask::rw-
other::---

The ACL suggests that I should have rw access, but kermit can't open the 
port.

Note that I removed all of my custom udev rules and ran udevadm control 
--reload-rules before performing this test.

I can sudo to workaround the problem, but I shouldn't have to.  Any 
ideas as to what is going on?


thanks,
galen
-- 
Galen Seitz
galens at seitzassoc.com