Re: [Owfs-developers] Issues with FTDI based USB-Serial dongle & DS2480B

[Paul A. <pau...@gm...>]

Ok, here is my code for mapping USB devices to tty devices. It's a script
and needs to be tested on various platforms.

-----------------------------------
#!/bin/sh

# find all directories with busnum (they are USB devices)
usbdirs=$(find /sys/devices -name "busnum" -printf "%h\n")

# look at every USB
for f in $usbdirs
do
b=$(cat $f/busnum)
d=$(cat $f/devnum)
p=$(cat $f/idProduct)
v=$(cat $f/idVendor)
 # find tty devices under each usb
t=$(find $f -name "tty[AU]*" -prune -printf "%f\n")
if [ -n "$t" ]
then
if [ $(echo $t | wc -w) == 1 ]
then
echo
echo $t
echo USB device number $d
echo $b:$d $v:$p
echo Full path: $f
fi
fi
done
-----------------------------------

On my desktop (Fedora with lots of devices:
ttyUSB6
USB device number 14
3:14 0711:0230
Full path:
/sys/devices/pci0000:00/0000:00:14.0/usb3/3-3/3-3.2/3-3.2.1/3-3.2.1.7/3-3.2.1.7.2

ttyUSB6
USB device number 12
3:12 0451:2036
Full path:
/sys/devices/pci0000:00/0000:00:14.0/usb3/3-3/3-3.2/3-3.2.1/3-3.2.1.7

ttyUSB6
USB device number 7
3:7 0409:0050
Full path: /sys/devices/pci0000:00/0000:00:14.0/usb3/3-3/3-3.2/3-3.2.1

ttyUSB0
USB device number 3
3:3 0403:6001
Full path: /sys/devices/pci0000:00/0000:00:14.0/usb3/3-4

ttyACM0
USB device number 39
1:39 04d8:f897
Full path: /sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.1

ttyUSB1
USB device number 33
1:33 0403:6001
Full path: /sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.3

ttyUSB7
USB device number 37
1:37 1a86:7523
Full path: /sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.4

I'll need to remove duplicates caused by hubs being included.
It looks like choosing either the longer path name or higher device number
can select the device and not hub.

Paul


On Tue, Sep 30, 2014 at 9:50 AM, Stefano Miccoli <mo...@ic...> wrote:

>
> On 30 Sep 2014, at 08:32, Johan Ström <jo...@st...> wrote:
>
> Hi all,
>
> picking this up again. Lets summarize the main points:
>
> * auto-detection can only be relied on for certain pure USB devices
> * auto-detection can not be relied on when "standard" serial bridge chips
> are used
> * if we can resolve /dev/ttyUSB0 to a particular USB device, we can
> potentially select a smarter (i.e. improved FTDI) code path instead of
> regular read/write from the tty device.
> * /dev/ttyUSB0 is not stable, unless explicit devd setup is done.
> * this makes alterantive OWFS device addressing interesting, by specifying
> USB serial. this would avoid devd all together.
>
>
> excellent recap. Let me add another remark.
>
> It seems that Debian, and most of the developers like to run owserver and
> companion programs as root. Personally I do not like this: on production
> systems I run owserver without root privileges, so udev/devd is still
> necessary to set appropriate permissions to /dev files.
>
> Unfortunately this means that with serial emulators some manual setup is
> needed: inspecting syslog files, noting the device serial number, modifying
> the udev/devd script. Alternatively owserver and family should drop root
> privileges after startup.
>
> Stefano
>
>
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