Greg Erskine wrote:
> I am curious about the remove rule. :confused:
>
> It looks like it will activate whenever *any* USB device is removed.
Yes, that's right.
When my DAC is connected, dmesg shows that it actually connects three
devices. In this example they are devices 10, 11 and 12 - a USB HUB,
the DAC, and something called DLCP, which I believe is the programming
interface.
Code:
--------------------
[170202.072564] usb 1-1.3: new full-speed USB device number 10 using
xhci_hcd
[170202.179417] usb 1-1.3: New USB device found, idVendor=0451,
idProduct=2036, bcdDevice= 1.01
[170202.179430] usb 1-1.3: New USB device strings: Mfr=0, Product=1,
SerialNumber=0
[170202.179441] usb 1-1.3: Product: General Purpose USB Hub
[170202.186528] hub 1-1.3:1.0: USB hub found
[170202.187410] hub 1-1.3:1.0: 2 ports detected
[170202.480562] usb 1-1.3.1: new full-speed USB device number 11 using
xhci_hcd
[170202.594599] usb 1-1.3.1: New USB device found, idVendor=08bb,
idProduct=2704, bcdDevice= 1.00
[170202.594611] usb 1-1.3.1: New USB device strings: Mfr=1, Product=2,
SerialNumber=0
[170202.594622] usb 1-1.3.1: Product: USB Audio DAC
[170202.594632] usb 1-1.3.1: Manufacturer: Burr-Brown from TI
[170202.631275] hid-generic 0003:08BB:2704.0005: hidraw0: USB HID v1.00
Device [Burr-Brown from TI USB Audio DAC ] on
usb-0000:01:00.0-1.3.1/input2
[170202.856569] usb 1-1.3.2: new full-speed USB device number 12 using
xhci_hcd
[170202.965778] usb 1-1.3.2: New USB device found, idVendor=04d8,
idProduct=ff89, bcdDevice= 0.01
[170202.965791] usb 1-1.3.2: New USB device strings: Mfr=1, Product=2,
SerialNumber=0
[170202.965801] usb 1-1.3.2: Product: DLCP
[170202.965811] usb 1-1.3.2: Manufacturer: Hypex BV
[170202.973646] hid-generic 0003:04D8:FF89.0006: hiddev96,hidraw1: USB HID
v1.11 Device [Hypex BV DLCP] on usb-0000:01:00.0-1.3.2/input0
--------------------
But there's plenty of information about each device, most notably the
idVendor and idProduct values, and these allow the 'add' rule to be
targeted very specifically so that it only fires for one of those three
devices.
However, when my DAC is disconnected, the only information reported by
dmesg is device number and the so-callled kernel name ($kernel), in this
case 1-1.3, 1-1.3.1 or 1-1.3.2. The idVendor and idProduct attributes
aren't available to filter the 'remove' rule.
Code:
--------------------
[183513.447152] usb 1-1.3: USB disconnect, device number 10
[183513.447171] usb 1-1.3.1: USB disconnect, device number 11
[183513.454398] usb 1-1.3.2: USB disconnect, device number 12
--------------------
Unfortunately, $kernel doesn't seem to be something that the rule can be
filtered on in the way that idVendor and idProduct are, but it CAN be
passed to the function that is called when the rule fires. So the
approach that the script takes is to record the kernel name associated
with the specific idVendor and idProduct into a file in the /tmp
directory, and then every time the 'remove' event is triggered, by
whatever USB device, the script compares the associated kernel name to
the one in the file, and only stops Squeezelite if they match. This
example from the script's log file shows it in action:
Code:
--------------------
[ 170202.63] Script parameters: restart DAC 1-1.3.1
[ 170202.64] DAC detected on 1-1.3.1
[ 170202.67] Attempting to start squeezelite
[ 170203.72] Restarting Squeezelite player...
Stopping Squeezelite player: Squeezelite...
Starting Squeezelite player: Squeezelite...
[ 183513.46] Script parameters: stop DAC 1-1.3.1:1.0
[ 183513.46] Script parameters: stop DAC 1-1.3.1:1.1
[ 183513.47] Script parameters: stop DAC 1-1.3:1.0
[ 183513.47] Script parameters: stop DAC 1-1.3.1:1.2
[ 183513.47] Script parameters: stop DAC 1-1.3.2:1.0
[ 183513.48] Script parameters: stop DAC 1-1.3.1
[ 183513.48] Script parameters: stop DAC 1-1.3.2
[ 183513.48] DAC on 1-1.3.1 removed
[ 183513.50] Stopping Squeezelite player: Squeezelite...
[ 183513.51] Script parameters: stop DAC 1-1.3
--------------------
With this approach, the script is briefly called for each of the devices
associated with the DAC, and it would be called also if I removed as USB
flash drive, but the script returns very quickly without doing anything,
except when the $kernel parameter matches the one associated with the
DAC device.
The file in the /tmp directory is created whenever the DAC is connected,
or, if it's already connected at boot, by the 'find' option, which gets
it from dmesg.
------------------------------------------------------------------------
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