On mer., 2014-05-21 at 13:50 -0400, Alan Stern wrote:
> On Wed, 21 May 2014, Mildred Ki'Lya wrote:
>
> > Hi,
> >
> > I have a problem with a USB device (4255:1000), running various kernels
> > from 3.12.6 (Fedora) up to 2.14.4 (ArchLinux). When I connect the
> > device, it appears all right. But after a few seconds of idle, it
> > disconnects itself.
...
>
> It's possible that the device can't handle Link Power Management.
> You can test this by writing 0 to the usb2_hardware_lpm file in the
> device's sysfs power directory:
>
> echo 0 >/sys/bus/usb/device/1-6/power/usb2_hardware_lpm
>
Thank you for your answer. I didn't have the opportunity to test until
today, and unfortunately I couldn't try this. There is no file
usb2_hardware_lpm for that device. It's possible the device doesn't
support this feature.
Do you have an idea of what else could go wrong with this device?
Here is the complete lsusb -v output for that device, it may help:
Bus 003 Device 032: ID 4255:1000
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.00
bDeviceClass 0 (Defined at Interface level)
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 64
idVendor 0x4255
idProduct 0x1000
bcdDevice 0.00
iManufacturer 1 Ambarella
iProduct 2 Storage
iSerial 3 123456789ABC
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 32
bNumInterfaces 1
bConfigurationValue 1
iConfiguration 0
bmAttributes 0xc0
Self Powered
MaxPower 4mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 2
bInterfaceClass 8 Mass Storage
bInterfaceSubClass 6 SCSI
bInterfaceProtocol 80 Bulk-Only
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x01 EP 1 OUT
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0200 1x 512 bytes
bInterval 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0200 1x 512 bytes
bInterval 0
Device Qualifier (for other device speed):
bLength 10
bDescriptorType 6
bcdUSB 2.00
bDeviceClass 0 (Defined at Interface level)
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 64
bNumConfigurations 1
Device Status: 0x0001
Self Powered
Many thanks,
Mildred
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