linux-kernel - Re: [linux-usb-devel] why was MODALIAS removed from usb kernel events? [u]

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Date:	Tue, 21 Aug 2007 10:39:58 +0200
From:	"Andreas Jellinghaus [c]" <aj@...hirelabs.com>
To:	Greg KH <greg@...ah.com>
Cc:	Kay Sievers <kay.sievers@...y.org>, linux-kernel@...r.kernel.org,
	linux-usb-devel@...ts.sourceforge.net
Subject: Re: [linux-usb-devel] why was MODALIAS removed from usb kernel events? [u]

Am Dienstag, 21. August 2007 schrieb Greg KH:
> On Fri, Aug 17, 2007 at 04:22:04PM +0200, Andreas Jellinghaus [c] wrote:
> > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit
> >diff;h=9f8b17e643fe6aa505629658445849397bda4e4f
> >
> > removes MODALIAS from one of the events,
>
> Which event?

here is the event with kernel 2.6.21:
UEVENT[1187683991.583384] 
add      /devices/pci0000:00/0000:00:1d.1/usb2/2-1/2-1.7/2-1.7:1.0 (usb)
ACTION=add
DEVPATH=/devices/pci0000:00/0000:00:1d.1/usb2/2-1/2-1.7/2-1.7:1.0
SUBSYSTEM=usb
SEQNUM=3070
PHYSDEVBUS=usb
DEVICE=/proc/bus/usb/002/006
PRODUCT=8e6/3438/100
TYPE=0/0/0
INTERFACE=11/0/0
MODALIAS=usb:v08E6p3438d0100dc00dsc00dp00ic0Bisc00ip00

note: it has both - MODALIAS and DEVICE.

here is the event with kernel 2.6.22 (with CONFIG_USB_DEVICE_CLASS):
UEVENT[1187684539.588975] 
add      /devices/pci0000:00/0000:00:1d.1/usb2/2-1/2-1.7/2-1.7:1.0 (usb)
ACTION=add
DEVPATH=/devices/pci0000:00/0000:00:1d.1/usb2/2-1/2-1.7/2-1.7:1.0
SUBSYSTEM=usb
SEQNUM=3029
DEVTYPE=usb_interface
PHYSDEVBUS=usb
INTERFACE=11/0/0
MODALIAS=usb:v08E6p3438d0100dc00dsc00dp00ic0Bisc00ip00

you see, it is missing DEVICE and PRODUCT and TYPE

and here is the event with kernel 2.6.22 with alans patch and 
CONFIG_USB_DEVICE_CLASS:

UEVENT[1187684125.860105] 
add      /devices/pci0000:00/0000:00:1d.1/usb2/2-1/2-1.7/2-1.7:1.0 (usb)
ACTION=add
DEVPATH=/devices/pci0000:00/0000:00:1d.1/usb2/2-1/2-1.7/2-1.7:1.0
SUBSYSTEM=usb
SEQNUM=3029
DEVTYPE=usb_interface
PHYSDEVBUS=usb
DEVICE=/proc/bus/usb/002/006
BUSNUM=002
DEVNUM=006
INTERFACE=11/0/0
MODALIAS=usb:v08E6p3438d0100dc00dsc00dp00ic0Bisc00ip00

it still misses PRODUCT and TYPE, for real compatibility those should be added 
too. (I can work around that, as the PRODUCT information is part of MODALIAS 
and I don't use TYPE.)

> If you enable CONFIG_USB_DEVICE_CLASS, does everything work the same
> again?

both with CONFIG_USB_DEVICE_CLASS. would it change anything here?

> What specific udev rule are you matching against here that is now
> broken?

still trying to get it to work, so far I try:

SUBSYSTEM!="usb", GOTO="openct_usb_rules_end"
ACTION!="add", GOTO="openct_usb_rules_end"
ENV{MODALIAS}=="usb:v0973p0001*", RUN+="/lib/udev/openct_usb"
ENV{MODALIAS}=="usb:*ic0Bisc00*", RUN+="/lib/udev/openct_usb"
LABEL="openct_usb_rules_end"

this should work?

> > The text does not mention MODALIAS nor the reason for it's removal.
>
> The reason is we don't need the usb_device class anymore, but we still
> provide for the compatibility if you have an old distro with old udev
> rules that is expecting it (only rule we ran into was the one for the
> usbfs /dev nodes, but there might be more.)

I'm no udev expert, but old kernels provide an event with all three 
informations I care about: MODALIAS, DEVICE and PRODUCT. this is changed,
and I don't understand what it has to do with usb_device class.

but I can say that without any event that has all three (or at least the first 
two - I can create PRODUCT from MODALIAS i think), I would need to redesign
how openct finds out if new devices are plugged in. long term I might need
to do so anyway, but right now people complain "it doesn't work" to me, and 
the culprit seems to be the kernel to me - 2.6.21 works, 2.6.22 does not.

Now I'm working on getting openct udev rules and handling script fixed so
they work at least with alans patch and work around missing PRODUCT.

Regards, Andreas
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