LinuxQuestions.org
Welcome to the most active Linux Forum on the web.
Go Back   LinuxQuestions.org > Forums > Linux Forums > Linux - Newbie
User Name
Password
Linux - Newbie This Linux forum is for members that are new to Linux.
Just starting out and have a question? If it is not in the man pages or the how-to's this is the place!

Notices


Reply
  Search this Thread
Old 06-21-2009, 07:40 AM   #1
arunlfc
LQ Newbie
 
Registered: Jan 2009
Posts: 21

Rep: Reputation: 15
usb devices in linux


Im using debian.
When i connect my usb stick to the computer, it is detected automatically and mounted as an scsi device(sda0). Why is that and what is the purpose of the various usb files in the device files' folder, like usbdev1.3_ep00 ?
Thanks,
Arun J.
 
Old 06-22-2009, 12:39 AM   #2
okos
Member
 
Registered: May 2007
Location: California
Distribution: Slackware/Ubuntu
Posts: 609

Rep: Reputation: 37
http://www.linux-usb.org/FAQ.html
 
Old 06-22-2009, 12:42 AM   #3
GrapefruiTgirl
LQ Guru
 
Registered: Dec 2006
Location: underground
Distribution: Slackware64
Posts: 7,594

Rep: Reputation: 551Reputation: 551Reputation: 551Reputation: 551Reputation: 551Reputation: 551
Without getting into great detail:

Many new(er) drives, like HDDs and CDROM drives and whatnot, are known as 'ATAPI' devices. ATAPI is a standard protocol, for lack of a better word at the moment, by which the computer communicates with the device. It's a standard which tries to allow for different manufacturers to all have their hardware communicate happily with each other.

Older stuff, simpler stuff, like old CD drives, scanners, old external hard disks, etc., used the SCSI protocol, which has been around longer.

However: ATAPI is actually a 'wrapper' for SCSI commands; in other words, deep down inside the hardware, ATAPI commands get translated into SCSI commands anyways.

I'm not sure in technical terms why stuff like USB devices and some CDROMs (even brand new ones) still use the SCSI protocol, rather than the ATAPI one, but I suppose that since USB is literally 'Universal Serial Bus' and SCSI was created when a fairly long time ago when external hardware was connected to serial and parallel ports, it still uses SCSI for that reason. The USB system is not like PATA/IDE or SATA, it's just a modern day serial port, and because of that, as far as USB goes, adding an ATAPI wrapper/layer onto it would be overkill, cumbersome, and unnecessary.

As for all the nodes and endpoints in /dev, well, everything in the machine pretty much, gets at least ONE node by which software and hardware can locate it, communicate with it, query it, etc. So when you plug in a USB device, a bunch of nodes get created, like for the device itself, the port it's plugged into, the hub that controls the port, the controller that controls the hub, etc.. It's a hierarchy of devices, each one getting its own identifying node.

Last edited by GrapefruiTgirl; 06-22-2009 at 12:49 AM.
 
Old 06-22-2009, 03:00 AM   #4
arunlfc
LQ Newbie
 
Registered: Jan 2009
Posts: 21

Original Poster
Rep: Reputation: 15
Thanks for the elaborate explanation grapefruit girl.
 
  


Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off



Similar Threads
Thread Thread Starter Forum Replies Last Post
Hotplugging USB devices in Linux jobless Programming 2 10-16-2008 08:34 PM
Can you use any USB devices in Linux? royeo Linux - Newbie 5 06-10-2006 09:35 PM
subforum for use of linux on usb devices darkRoom LQ Suggestions & Feedback 4 03-27-2004 06:36 AM
USB Devices in Linux not working bluedude2288 Linux - Hardware 3 11-02-2003 10:34 AM
Linux and USB devices jaycee999 Linux - Newbie 5 03-20-2002 09:47 PM


All times are GMT -5. The time now is 04:24 PM.

Main Menu
Advertisement
My LQ
Write for LQ
LinuxQuestions.org is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
Syndicate
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
Facebook: linuxquestions Google+: linuxquestions
Open Source Consulting | Domain Registration