On Sat, 27 Aug 2005, Singh, Brijeshkumar wrote:

> Hi Alan,
> 
> Now I have test the below cases on IBM R51 laptop which comes with two
> external USB ports (side top and bottom). I am using here one pendrives
> (Texas 1GB and IBM 512MB) and a Mouse.

Part of your confusion is caused by the fact that a single physical port
can be mapped to two different buses: high-speed and full/low-speed.  The
port will thus have a different number depending on the speed of the
device plugged into it.  In this case, your high-speed bus is Bus 4 and
your full/low-speed bus is Bus 2.  I don't know what Bus 1 and Bus 3 are
doing here; probably they are controllers present on the motherboard but
not actually connected to anything at all.

Another part of your confusion is that you made a mistake in step 3 below
when preparing your email message.

I'm going to cut out all the unimportant lines from your listings here.

> 1- Plug Texas memory key on top and usb mouse on the bottom port.
> 
> tux usb_20 # lsusb
> Bus 004 Device 016: ID 0451:625f Texas Instruments, Inc.
> Bus 002 Device 016: ID 04b4:0001 Cypress Semiconductor Corp. Mouse
> 
> T:  Bus=04 Lev=01 Prnt=01 Port=03 Cnt=01 Dev#= 16 Spd=480 MxCh= 0
> ----------------------------^
> I:  If#= 0 Alt= 0 #EPs= 2 Cls=08(stor.) Sub=06 Prot=50 Driver=usb-storage
> T:  Bus=02 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#= 16 Spd=1.5 MxCh= 0
> -----------------------------^
> I:  If#= 0 Alt= 0 #EPs= 1 Cls=03(HID  ) Sub=01 Prot=02 Driver=usbhid

This shows that the top connector on bus 4 is port 4 (3+1) and the bottom
connector on bus 2 is port 1 (0+1).  (If you're wondering why there should
be a port number 4 when the computer has only two connectors, the answer
is that the controller's inputs corresponding to ports 1, 2, 5, and 6
aren't connected to anything.  No doubt those inputs are mapped to the 
same non-existent locations as the inputs for Bus 1 and Bus 3.)

> 2- Plug IBM key on side top port
> 
> tux usb_20 # lsusb
> Bus 002 Device 017: ID 08ec:0011 M-Systems Flash Disk Pioneers
> Bus 002 Device 016: ID 04b4:0001 Cypress Semiconductor Corp. Mouse
> 
> T:  Bus=02 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#= 16 Spd=1.5 MxCh= 0
> -----------------------------^
> I:  If#= 0 Alt= 0 #EPs= 1 Cls=03(HID  ) Sub=01 Prot=02 Driver=usbhid
> T:  Bus=02 Lev=01 Prnt=01 Port=01 Cnt=02 Dev#= 17 Spd=12  MxCh= 0
> ------------------------------^
> I:  If#= 0 Alt= 0 #EPs= 2 Cls=08(stor.) Sub=06 Prot=50 Driver=usb-storage

This shows that the top connector on bus 2 is port 2 (1+1).  The bottom 
connector on bus 2 is still port 1.

> 3- Plug Texas on top side and IBM key on bottom

No.  You plugged the Texas Instruments device into the bottom connector
and kept the IBM key plugged into the top connector.

> tux usb_20 # lsusb
> Bus 004 Device 021: ID 0451:625f Texas Instruments, Inc.
> Bus 002 Device 019: ID 08ec:0011 M-Systems Flash Disk Pioneers
> 
> T:  Bus=04 Lev=01 Prnt=01 Port=02 Cnt=01 Dev#= 21 Spd=480 MxCh= 0
> -------------------------------^
> I:  If#= 0 Alt= 0 #EPs= 2 Cls=08(stor.) Sub=06 Prot=50 Driver=usb-storage
> T:  Bus=02 Lev=01 Prnt=01 Port=01 Cnt=01 Dev#= 19 Spd=12  MxCh= 0
> -------------------------------^
> I:  If#= 0 Alt= 0 #EPs= 2 Cls=08(stor.) Sub=06 Prot=50 Driver=usb-storage

This shows that the bottom connector on bus 4 is port 3 (2+1) and the top 
connector on bus 2 is still port 2.

> I am not able to conclude on which port the device is connected using
> USB toplogy section. I googled to understand this information which did
> not find exact method of doing so. Each method chanages once I plug a
> new device or reboot the system.

I have just shown you how to figure this out.

> I nut i need the below information from proc interface
>  
> a) One which device node (/dev/sd[a-z]) the storage device is detected.
> b) Whether the connected storage device is CD-ROM/FLOPPY/MEMORY KEY
> c) On which port the device is connected.

I believe you already know the answer to a).  b) is essentially impossible 
to figure out -- you can tell the difference between a CD and 
direct-access device easily enough, but there's no reliable way of telling 
whether a device is a floppy drive.  And I've just given you the answer 
for c).

Alan Stern



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