Linuxusb driver debugging: This is the linuxusb driver debugging-003: A detailed page for preparation under Ubuntu. It introduces the knowledge, skills, and experience related to Linux, and some Linux source code. Preparations in Ubuntu: (1) how to view the printk output in the kernel: dmesg
Combined with the pipeline command, dmesg | head, dmesg | tail can see the content output by printk in the pipeline. This is a useful tool. (2) USB packet capture tool: usb_mon, in fact, Ubuntu has a built-in USB packet capture tool --- usb_mon [In fact, make menuconfig will let us choose] The usage method is as follows: # Mount-T debugfs NONE/sys/kernel/debug
# Modprobe usbmon
View the current USB device:
# Cat/sys/kernel/debug/USB/devices
The following output:
T: Bus = 01 lev= 01 prnt = 01 port = 00 CNT = 01 Dev # = 12 SPD = 480 mxch = 0
D: ver = 2.00 CLS = 00 (> IFC) sub = 00 prot = 00 mxps = 64 # cfgs = 1
P: Vendor = 601a ProdID = 4740 Rev = 1.00
S: Manufacturer = Ingenic
S: Product = JZ4740 USB Boot Device
C: * # Ifs = 1 Cfg # = 1 xcode = c0 MxPwr = 2mA
I: * If # = 0 Alt = 0 # EPs = 2 Cls = ff (vend.) Sub = 00 Prot = 50 Driver = skeleton
E: Ad = 01 (O) 2.2.02( Bulk) MxPS = 512 Ivl = 0 ms
E: Ad = 81 (I) 2.2.02 (Bulk) MxPS = 512 Ivl = 0 ms
How can I understand the above output? Documentation/usb/usbmon.txt
Bus = 01 means it's bus 1.
We can find the Bus number of our device through the above Vendor = 601a ProdID. Above Bus = 01. Use the following fame and fortune to listen to all USB packets on Bus01.
# Cat/sys/kernel/debug/usb/usbmon/1u
To start listening to all USB packets on all buses:
# Cat/sys/kernel/debug/usb/usbmon/0u
Once a packet exists, it is printed:
# Cat/sys/kernel/debug/USB/usbmon/1u
F07dbb80 3233986312 s co: 1: 012: 0 s 40 01 80c0 0000 0000 0
F07dbb80 3234327703 c co: 1: 012: 0 0 0
F07dbb80 3234327880 s co: 1: 012: 0 s 40 02 0000 0200 0000 0
F07dbb80 3234329561 c co: 1: 012: 0 0 0
F07dbb80 3234329625 s bi: 1: 012: 1-115 32 <
F07dbb80 3234331550 C bi: 1: 012: 1-75 32 = 00000000 00000000... For more information, see the USB mon.txt urb tag.
Timestamp: milliseconds
Event Type: S-submission, C-callback, E-submission error.
URBType: BusNo: DeviceAddr: EndPointNum
Ci Co Control input and output
Zi Zo Isochronous input and output
Ii Io Interrupt input and output
Bi Bo Bulk input and output
URB Status: 0 indicates no error. -XXX is the error code.
