> This is a good example. The kernel prints a warning message in the log
> when it sees an unpowered hub plugged into another unpowered hub. The
> fact that the warning isn't present in your log means that the hubs lie
> to the kernel: They don't tell it they are unpowered. Another way to
> see this is that the log doesn't include any messages about "hub
> controller current requirement"; these messages are skipped when the
> hub claims to be self-powered.
>
> You should be able to see this in the "lsusb -v" output for those hubs.
>
Ya with lsusb -v , hubs do claim to be sef powered .
lsusb -v log is attached .
1) But by lying to the kernel , what advantage do bus - powered hubs get ?
can we conclude that such hubs design is not proper ?
Thanx for the reply .
Regards
Amit Nagal
Bus 001 Device 002: ID 05e3:0608 Genesys Logic, Inc. USB-2.0 4-Port HUB
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.00
bDeviceClass 9 Hub
bDeviceSubClass 0 Unused
bDeviceProtocol 1 Single TT
bMaxPacketSize0 64
idVendor 0x05e3 Genesys Logic, Inc.
idProduct 0x0608 USB-2.0 4-Port HUB
bcdDevice 9.01
iManufacturer 0
iProduct 1 USB2.0 Hub
iSerial 0
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 25
bNumInterfaces 1
bConfigurationValue 1
iConfiguration 0
bmAttributes 0xe0
Self Powered
Remote Wakeup
MaxPower 100mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 1
bInterfaceClass 9 Hub
bInterfaceSubClass 0 Unused
bInterfaceProtocol 0 Full speed (or root) hub
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 3
Transfer Type Interrupt
Synch Type None
Usage Type Data
wMaxPacketSize 0x0001 1x 1 bytes
bInterval 12
Hub Descriptor:
bLength 9
bDescriptorType 41
nNbrPorts 4
wHubCharacteristic 0x00e0
Ganged power switching
Ganged overcurrent protection
TT think time 32 FS bits
Port indicators
bPwrOn2PwrGood 50 * 2 milli seconds
bHubContrCurrent 100 milli Ampere
DeviceRemovable 0x00
PortPwrCtrlMask 0xff
Hub Port Status:
Port 1: 0000.0100 power
Port 2: 0000.0100 power
Port 3: 0000.0100 power
Port 4: 0000.0100 power
Device Qualifier (for other device speed):
bLength 10
bDescriptorType 6
bcdUSB 2.00
bDeviceClass 9 Hub
bDeviceSubClass 0 Unused
bDeviceProtocol 0 Full speed (or root) hub
bMaxPacketSize0 64
bNumConfigurations 1
Device Status: 0x0001
Self Powered
