Re: [PATCH RFC V3.5] leds: trigger: Introduce an USB port trigger

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On 08/25/2016 04:30 PM, Alan Stern wrote:
On Thu, 25 Aug 2016, Jacek Anaszewski wrote:

I'd see it as follows:

#cat available_ports
#1-1 1-2 2-1

#echo "1-1" > new_port

#cat observed_ports
#1-1

#echo "2-1" > new_port

#cat observed_ports
#1-1 2-1

We've already had few discussions about the sysfs designs trying
to break the one-value-per-file rule for LED class device, and
there was always strong resistance against.

This scheme has multiple values in both the available_ports and
observed_ports files.  :-(  Not that I have any better suggestions...

Right, I forgot to add a note here, that this follows space
separated list pattern similarly as in case of triggers attribute.
Of course other suggestions are welcome.

Also a description of the device connected to the port would be a nice
feature, however I am not certain about the feasibility thereof.

What kind of description do you mean? Where should it be used / where
should it appear?


Product name/symbol. Actually it should be USB subsystem responsibility
to provide the means for querying the product name by port id, if it
is possible at all.

	cat /sys/bus/usb/devices/PORT/product
	cat /sys/bus/usb/devices/PORT/manufacturer

These will work if there is a device registered under PORT.

I've found only idProduct and idVendor files. They indeed uniquely
identify the device, but the numbers are not human readable.
Is there a way to retrieve the corresponding names in kernel?
Does the lsusb command do the mapping in the user space or maybe
it takes the names from kernel?

--
Best regards,
Jacek Anaszewski
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