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I have yet to plug a USB device into any of our Ubuntu machines and have the computer immediately recognize it and put up an icon. I would like to ...
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- 12-02-2006 #1
- Join Date
- Jun 2006
Reluctant USB devices
I would like to better understand what is happening within Linux with USB devices. If one gives the terminal command lsusb -v , a lot of information comes up (example quoted from such output for 'Bus 001 Device 001...below) but I am unsure what much of it means. I assume that some of it refers to the bus whether something is plugged in or not, and other of it refers to the device that is plugged in.
I assume that at bootup Linux first sets up some sort of communications with the USB ports so that if anything gets plugged in, the presence of the device is recognized.
Then presumeably Linux tries to figure out what it is, and if successful, somehow allow user accessability/use of the device.
So if a user wants to confirm that Linux:
-is aware of the device presence, and
-has or has not identified the device
regardless of whether the device is a flash memory (thumbdrive sort of thing), hard disk drive, CD or DVD reader or reader-writer:
what are the various things going on inside Linux so that these things can be consistently determined?
So is anyone able to explain in relatively simple terms what goes on from bootup differentiating between bus and device, especially including any commands that lead one to the information?
Resource referral is welcome, but most of what I have googled up is in pretty deep technical language and I am looking for something more oriented toward newbies. TIA.
From lsusb -v :
Bus 001 Device 001: ID 0000:0000 Device Descriptor: bLength 18 bDescriptorType 1 bcdUSB 1.10 bDeviceClass 9 Hub bDeviceSubClass 0 Unused bDeviceProtocol 0 bMaxPacketSize0 8 idVendor 0x0000 idProduct 0x0000 bcdDevice 2.06 iManufacturer 3 iProduct 2 iSerial 1 bNumConfigurations 1 Configuration Descriptor: bLength 9 bDescriptorType 2 wTotalLength 25 bNumInterfaces 1 bConfigurationValue 1 iConfiguration 0 bmAttributes 0xe0 Self Powered Remote Wakeup MaxPower 0mA Interface Descriptor: bLength 9 bDescriptorType 4 bInterfaceNumber 0 bAlternateSetting 0 bNumEndpoints 1 bInterfaceClass 9 Hub bInterfaceSubClass 0 Unused bInterfaceProtocol 0 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 0x0002 1x 2 bytes Self Powered Remote Wakeup MaxPower 0mA Interface Descriptor: bLength 9 bDescriptorType 4 bInterfaceNumber 0 bAlternateSetting 0 bNumEndpoints 1 bInterfaceClass 9 Hub bInterfaceSubClass 0 Unused bInterfaceProtocol 0 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 0x0002 1x 2 bytes bInterval 255
- 12-04-2006 #2
- Join Date
- Jun 2006
To further refine my question, I assume that all distros operate the same way, but please advise if not. I am using Ubuntu 6.06.
First is the layer of hardware that the USB ports are connected to. Does Linux always use the same directory to place files that "connect" the motherboard to these ports? If so, which directory? If possible to say, what files?
Then when a USB device is plugged in, Linux must record the event. Where? In what files?
Assuming that it recognizes the device, Linux must make a file or record in a file the details of the device. Where and how does one see it?