Hello,
Like to thank Henry Gebhardt, Greg KH and Alan Stern for
helping me out with answering the USB
questions that I posed to this list. Continuing with my learning USB,
I have the following doubt...
On connecting a USB pendrive and viewing the /proc/bus/usb/devices I get
the endpoint addresses assigned as
E: Ad=01(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E: Ad=82(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
Here the OUT endpoint is address 1 and IN is address 2, this I can
understand because the endpoints have been assigned different addresses.
But on connecting another USB mass storage device, I get this
T: Bus=01 Lev=01 Prnt=01 Port=03 Cnt=02 Dev#= 6 Spd=480 MxCh= 0
D: Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs= 1
P: Vendor=0bc2 ProdID=2000 Rev= 0.00
S: Manufacturer=Seagate
S: Product=FreeAgent Go
S: SerialNumber= 5MA7YVCP
C:* #Ifs= 1 Cfg#= 1 Atr=80 MxPwr=500mA
I:* If#= 0 Alt= 0 #EPs= 2 Cls=08(stor.) Sub=06 Prot=50
Driver=usb-storage
E: Ad=01(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E: Ad=81(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
Here both OUT and IN endpoints have been assigned the address 1 !! Is
this normal behavior? When a packet is sent by the host to the device
with address 6, with just one interface, can both endpoints be assigned
the same address?
I also read that we can have a total of 16 endpoints (hard limit 30) for
a single interface. With just OUT and IN being the only endpoints a
particular interface can possibly have, what is the need for the other
14 endpoints?
Thanks in advance,
Regards,
Nicholas
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