Re: [Linux-uvc-devel] Support for Interface Association Descriptors

[Craig N. <cr...@na...>]

    I've put together a patch demonstrating how Interface Association
Descriptors could be supported with a minimal amount of changes the
current USB stack. When a USB device is enumerated the descriptors are
parsed by the code in drivers/usb/core/config.c. A list of IADs for a
given configuration would be stored in the usb_host_config struct for
that configuration. If an interface is referenced by an IAD then a
pointer to the IAD will be stored in the usb_host_interface struct for
that interface.
    The probe entry point of a class driver could check if the interface
it's probing is referenced by an IAD. If it is then configure the driver
to handle the other associated interfaces as well. The probe function
could also check the "extra" and "extralen" fields in the
usb_host_interface struct for each interface to get the class specific
descriptors.

The code that displays descriptor information in /proc/bus/usb/devices
will show IADs in the following format:

A:  1stIf= 0 IfCount= 2 Cls=ff(vend.) Sub=03 Prot=00


With the patch the descriptors for the Logitech QuickCam Pro 5000 are
shown in /proc/bus/usb/devices as:

T:  Bus=03 Lev=01 Prnt=01 Port=04 Cnt=01 Dev#=  3 Spd=480 MxCh= 0
D:  Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=01 MxPS=64 #Cfgs=  1
P:  Vendor=046d ProdID=08c5 Rev= 0.05
C:* #Ifs= 4 Cfg#= 1 Atr=80 MxPwr=500mA
A:  1stIf= 0 IfCount= 2 Cls=ff(vend.) Sub=03 Prot=00
A:  1stIf= 2 IfCount= 2 Cls=01(audio) Sub=02 Prot=00
I:  If#= 0 Alt= 0 #EPs= 1 Cls=ff(vend.) Sub=01 Prot=00 Driver=(none)
E:  Ad=87(I) Atr=03(Int.) MxPS=  16 Ivl=16ms
I:  If#= 1 Alt= 0 #EPs= 0 Cls=ff(vend.) Sub=02 Prot=00 Driver=(none)
I:  If#= 1 Alt= 1 #EPs= 1 Cls=ff(vend.) Sub=02 Prot=00 Driver=(none)
E:  Ad=81(I) Atr=01(Isoc) MxPS= 192 Ivl=125us
I:  If#= 1 Alt= 2 #EPs= 1 Cls=ff(vend.) Sub=02 Prot=00 Driver=(none)
E:  Ad=81(I) Atr=01(Isoc) MxPS= 384 Ivl=125us
I:  If#= 1 Alt= 3 #EPs= 1 Cls=ff(vend.) Sub=02 Prot=00 Driver=(none)
E:  Ad=81(I) Atr=01(Isoc) MxPS= 512 Ivl=125us
I:  If#= 1 Alt= 4 #EPs= 1 Cls=ff(vend.) Sub=02 Prot=00 Driver=(none)
E:  Ad=81(I) Atr=01(Isoc) MxPS= 640 Ivl=125us
I:  If#= 1 Alt= 5 #EPs= 1 Cls=ff(vend.) Sub=02 Prot=00 Driver=(none)
E:  Ad=81(I) Atr=01(Isoc) MxPS= 800 Ivl=125us
I:  If#= 1 Alt= 6 #EPs= 1 Cls=ff(vend.) Sub=02 Prot=00 Driver=(none)
E:  Ad=81(I) Atr=01(Isoc) MxPS= 944 Ivl=125us
I:  If#= 1 Alt= 7 #EPs= 1 Cls=ff(vend.) Sub=02 Prot=00 Driver=(none)
E:  Ad=81(I) Atr=01(Isoc) MxPS=1280 Ivl=125us
I:  If#= 1 Alt= 8 #EPs= 1 Cls=ff(vend.) Sub=02 Prot=00 Driver=(none)
E:  Ad=81(I) Atr=01(Isoc) MxPS=1600 Ivl=125us
I:  If#= 1 Alt= 9 #EPs= 1 Cls=ff(vend.) Sub=02 Prot=00 Driver=(none)
E:  Ad=81(I) Atr=01(Isoc) MxPS=1984 Ivl=125us
I:  If#= 1 Alt=10 #EPs= 1 Cls=ff(vend.) Sub=02 Prot=00 Driver=(none)
E:  Ad=81(I) Atr=01(Isoc) MxPS=2688 Ivl=125us
I:  If#= 1 Alt=11 #EPs= 1 Cls=ff(vend.) Sub=02 Prot=00 Driver=(none)
E:  Ad=81(I) Atr=01(Isoc) MxPS=3060 Ivl=125us
I:  If#= 2 Alt= 0 #EPs= 0 Cls=01(audio) Sub=01 Prot=00 Driver=(none)
I:  If#= 3 Alt= 0 #EPs= 0 Cls=01(audio) Sub=02 Prot=00 Driver=(none)
I:  If#= 3 Alt= 1 #EPs= 1 Cls=01(audio) Sub=02 Prot=00 Driver=(none)
E:  Ad=86(I) Atr=05(Isoc) MxPS=  16 Ivl=1ms
I:  If#= 3 Alt= 2 #EPs= 1 Cls=01(audio) Sub=02 Prot=00 Driver=(none)
E:  Ad=86(I) Atr=05(Isoc) MxPS=  32 Ivl=1ms
I:  If#= 3 Alt= 3 #EPs= 1 Cls=01(audio) Sub=02 Prot=00 Driver=(none)
E:  Ad=86(I) Atr=05(Isoc) MxPS=  48 Ivl=1ms