Am Fri, 16 Jan 2009 22:30:21 -0600 (CST) schrieb Mike Isely <[email protected]>:
> > Carsten: > > I just learned something interesting that you'll want to know. The > serial number *is* in fact already available in the USB configuration > data. Thus you can do what Mauro is suggesting to identify the > device: Use the bus_info field to find the udev-populated device node > in /sys and then walk that to find the serial number. > > The reason I had never considered this is because the device's serial > number is stored in its ROM, encoded in a format that is specific to > Hauppauge and has nothing to do with USB. The pvrusb2 driver reads > this by using the tveeprom module to parse the data. Since the > pvrusb2 driver then never does anything with the result except to use > it as the root node in its own sysfs interface, I had concluded that > it wasn't available any other way. > > However it is in fact present in the USB configuration data. Just > run the usbview generic tool and you'll see it. You'll see a field > labeled "Serial Number:" and its value will be of the form > "mmmm-xx-yyyyyyyy". The "mmmm" appears to match the model type, but > the "yyyyyyyy" is an 8 digit hex number that when converted to > decimal will match the number that the pvrusb2 driver puts in its > sysfs interface. (The "xx" part appears to just be a pair of > constant zeroes.) > > Why is this? Well I can't prove it, but I can think of two > possibilities for how the serial number could have found its way into > the USB configuration data without any help from the pvrusb2 driver: > > First the USB config data is also in that ROM - this is where the > manufacturer and device ID are initially coded of course. But that's > a different part of the ROM, formatted in a manner that the FX2 > processor's factory ROM initialization can directly read, i.e. this > part is not specific to Hauppauge. So it's possible that the serial > number is actually written in two places. > > A second possibility is that the FX2 is able to directly reinitialize > its USB interface as it comes up. It can write its own configuration > data. So it's theoretically possible that the Hauppauge-supplied FX2 > firmware is itself accessing the nearby Hauppauge ROM, extracting the > serial number, and then stuffing it in to the USB configuration > data. However until now I've never seen any actual evidence that the > FX2 firmware will directly read that ROM (rather, the host driver > reads it). > > But either way that would explain things. > > -Mike > Hi, I'm now diving into sysfs and found the info you mentioned in "/sys/bus/usb/devices/7-2/" for a bus_info-string of "usb 7-2 address 6" The "address 6" part is found in "/sys/bus/usb/devices/7-2/devnum" and is the part which causes the trouble with my simple bus_info-approach because it always changes. Some questions about now two possible approaches:: Approach #1: Direct mapping of card and bus_info to config data (my original idea): - To make the simple bus_info approach work, just the address 6 has to be removed from the bus_info-string. Is it neccessary to identify the device in sysfs? (should it really be there?) Approach #2: Use bus_info-string to locate device-information in sysfs and read infos like serial from there: - How does the canonical usb-bus_info-string look like which has been suggested by Mauro on the linux-media-list? - How to make my app work with PCI-devices? (because I have to look in "/sys/bus/usb/" for USB-devices) How to distingish USB- and PCI-devices from v4l2? Of course, both approaches could be combined if bus_info would return something like "USB-7-2" which doesn't change and is suitable for finding the serial via sysfs. Sorry for all those questions. I know you are a driver-developer, not my personal teacher, but you know about the problem I have ;) I already read the sysfs-reference at http://www.kernel.org/pub/linux/kernel/people/mochel/doc/papers/ols-2005/ but it doesn't contain much information for my case. Regards, Carsten _______________________________________________ pvrusb2 mailing list [email protected] http://www.isely.net/cgi-bin/mailman/listinfo/pvrusb2
