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1 swift 1.1 <?xml version='1.0' encoding="UTF-8"?>
2 swift 1.20 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/usb-guide.xml,v 1.19 2009/11/30 07:29:20 nightmorph Exp $ -->
3 swift 1.1 <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
4    
5 swift 1.20 <guide>
6 swift 1.1 <title>Gentoo Linux USB Guide</title>
7    
8     <author title="Author">
9 fox2mike 1.4 <mail link="fox2mike@gentoo.org">Shyam Mani</mail>
10 swift 1.1 </author>
11    
12     <abstract>
13     This document helps a user setup USB on a Gentoo system and configure various
14     USB devices as well.
15     </abstract>
16    
17     <!-- The content of this document is licensed under the CC-BY-SA license -->
18 fox2mike 1.5 <!-- See http://creativecommons.org/licenses/by-sa/2.5 -->
19 swift 1.1 <license/>
20    
21 nightmorph 1.19 <version>1.15</version>
22     <date>2009-11-29</date>
23 swift 1.1
24     <chapter>
25     <title>Introduction</title>
26     <section>
27     <title>What is USB?</title>
28     <body>
29    
30     <p>
31 neysx 1.3 USB stands for Universal Serial Bus and is basically an external interface
32     standard that enables communication between the computer and various other
33     peripherals. Some of the most commonly used USB devices today are keyboards,
34     mice, pen drives, digital cameras, external CD &amp; DVD writers, printers etc.
35 swift 1.1 </p>
36    
37     <p>
38 neysx 1.3 There are currently two versions of USB in use, i.e. USB 1.1 and USB 2.0.
39     Since USB has always been backward compatible with its previous versions,
40     USB 2.0 is backwards compatible with USB 1.1. The latest USB devices are
41     typically USB 2.0 compatible. USB 2.0 supports a maximum data transmission
42     speed of 480 Mbps or 60 MBps and this is the major difference between the two
43     standards. Another advantage with USB is that the devices are all
44     <e>hot-pluggable</e>, which means that you do not have to restart your system
45 swift 1.1 in order for you to be able to use these devices.
46     </p>
47    
48     </body>
49     </section>
50     <section>
51     <title>A Technical Perspective</title>
52     <body>
53    
54     <p>
55 neysx 1.3 Before we go onto the exact configuration options in the kernel, it would
56     be apt to look at USB in a little more detail. If you're in a hurry or want
57 swift 1.17 to skip this section, please go to <uri link="#kernel">Kernel
58     Configuration</uri>.
59 swift 1.1 </p>
60    
61     <p>
62 neysx 1.3 A USB system has a host controller, hubs, a <e>root hub</e> amongst others
63     and can support up to 127 USB devices including the hubs. The host controller
64     is nothing but the hardware interface between the USB device and the
65     operating system. There are a couple of HCI (Host Controller Interface)
66     in use today and they are the OHCI (Open HCI) by Compaq, UHCI (Universal HCI)
67     and EHCI (Enhanced HCI), both from Intel. The OHCI/UHCI are the two industry
68 swift 1.1 standard USB 1.1 interfaces whereas the EHCI is for USB 2.0.
69     </p>
70    
71     <p>
72 neysx 1.3 The hardware vendor provides an interface for the programmer that allows
73     the system to interact with the hardware and this is called the HCD or Host
74     Controller Device. It is through this HCD that the device interacts with the
75 swift 1.1 system software. The following diagram should make things easier to comprehend.
76     </p>
77    
78     <pre caption="General USB Architecture">
79 neysx 1.3 <comment>(Software consists of other components as well like the device driver, but
80     for the sake of simplicity, they are not shown)</comment>
81 swift 1.1
82 neysx 1.3 + ---- Hardware ---- + ---- Software ---- +
83 swift 1.1 | | |
84 neysx 1.3 | [USB Dev] -+-> {EHCI} -+---> ( EHCD ) |
85 swift 1.1 | | | | User
86     | `-> {UHCI} -+---> ( UHCD ) |
87     | | |
88     + ---- Hardware ---- + ---- Software ---- +
89 neysx 1.3 </pre>
90 swift 1.1
91     <p>
92 neysx 1.3 A USB device can either use a custom driver or use one already present in
93     the system and this is based on the concept of a device <e>class</e>. This
94     means that if a device belongs to a certain <e>class</e>, then other devices
95     belonging to the same <e>class</e> can make use of the same device driver.
96     Some of these <e>classes</e> are the USB HID (Human Interface Devices) class
97     which covers input devices like keyboards and mice, the USB Mass Storage
98     devices class which covers devices like pen drives, digital cameras, audio
99     players etc and the USB CDC (Communication Devices Class) which essentially
100 swift 1.1 covers USB modems and similar devices.
101     </p>
102    
103     </body>
104     </section>
105 fox2mike 1.5 <section>
106 swift 1.1 <title>What's on your machine?</title>
107     <body>
108    
109     <p>
110     It is very simple to find out whether your machine has USB 2.0 support or not.
111     We make use of the <c>lspci</c> command for this purpose.
112     </p>
113    
114     <note>
115 neysx 1.3 The <c>lspci</c> tool is a part of the <c>sys-apps/pciutils</c> package. If
116     you do not have this installed, please <c>emerge pciutils</c>. Please note
117 swift 1.1 that you have to be root while running the <c>lspci</c> command.
118     </note>
119    
120     <pre caption="Various lspci outputs">
121     <comment>(In system that is USB 1.1 compliant, note the UHCI only)</comment>
122    
123     # <i>lspci -v | grep USB</i>
124     0000:00:04.2 USB Controller: Intel Corp. 82371AB/EB/MB PIIX4 USB (rev 01) (prog-if 00 [UHCI])
125    
126     <comment>(A system that is USB 2.0 compliant, note the EHCI and UHCI)</comment>
127    
128     00:1d.0 USB Controller: Intel Corp. 82801DB USB (Hub #1) (rev 01) (prog-if 00 [UHCI])
129     00:1d.1 USB Controller: Intel Corp. 82801DB USB (Hub #2) (rev 01) (prog-if 00 [UHCI])
130     00:1d.2 USB Controller: Intel Corp. 82801DB USB (Hub #3) (rev 01) (prog-if 00 [UHCI])
131     00:1d.7 USB Controller: Intel Corp. 82801DB USB EHCI Controller (rev 01) (prog-if 20 [EHCI])
132     </pre>
133    
134     <p>
135 neysx 1.3 So using the <c>lspci</c> command, we can find out if the system supports
136     USB 2.0. This is useful as we will be enabling the corresponding options in
137 swift 1.1 the kernel.
138     </p>
139    
140     </body>
141     </section>
142     </chapter>
143    
144     <chapter id="kernel">
145     <title>Kernel Configuration</title>
146     <section>
147     <title>Getting the kernel</title>
148     <body>
149    
150     <p>
151 neysx 1.3 First emerge the kernel sources of your choice. Here we'll use the
152 swift 1.6 <c>gentoo-sources</c>. For more information on the various kernel sources
153 neysx 1.3 available on Portage, please look up the <uri
154     link="/doc/en/gentoo-kernel.xml">Gentoo Linux Kernel Guide</uri>.
155 swift 1.1 </p>
156    
157     <pre caption="Getting the kernel sources">
158 neysx 1.3 # <i>emerge gentoo-sources</i>
159 swift 1.1 </pre>
160    
161     <p>
162     Now, lets get on with the task of configuring the kernel.
163     </p>
164    
165     <pre caption="Heading over to the source">
166 neysx 1.3 # <i>cd /usr/src/linux</i>
167     # <i>make menuconfig</i>
168 swift 1.1 </pre>
169    
170     <note>
171 neysx 1.3 The above example assumes that <path>/usr/src/linux</path> symlink points to
172 swift 1.1 the kernel sources you want to use. Please ensure the same before proceeding.
173     </note>
174    
175     </body>
176     </section>
177 nightmorph 1.18 <section>
178     <title>Config options for the kernel</title>
179 swift 1.1 <body>
180    
181     <p>
182 nightmorph 1.18 Now we will look at some of the options we will have to enable in the kernel to
183     ensure proper USB support for our devices.
184 swift 1.1 </p>
185    
186     <note>
187 neysx 1.3 Examples in this document will show configuration options for basic USB
188     support as well as those needed commonly, for example a USB mass storage
189     device (most cameras and USB pen drives). If you have a specific USB device
190     that needs to be configured, please look up your device's manual or search
191     online to see if that device has support built-in into the kernel or custom
192     drivers that you can use. Please note that for the sake of ease, all examples
193     have the options compiled into the kernel. If you would like to have a modular
194     kernel, ensure that you note down the various modules and adjust your config
195 swift 1.1 files accordingly.
196     </note>
197    
198 nightmorph 1.18 <pre caption="make menuconfig options">
199 swift 1.1 Device Drivers ---&gt;
200     SCSI device support ---&gt;
201    
202 neysx 1.3 <comment>(Although SCSI will be enabled automatically when selecting USB Mass Storage,
203     we need to enable disk support.)</comment>
204 swift 1.1 --- SCSI support type (disk, tape, CD-ROM)
205     &lt;*&gt; SCSI disk support
206    
207     <comment>(Then move back a level and go into USB support)</comment>
208     USB support ---&gt;
209    
210 neysx 1.3 <comment>(This is the root hub and is required for USB support.
211     If you'd like to compile this as a module, it will be called usbcore.)</comment>
212     &lt;*&gt; Support for Host-side USB
213 swift 1.1
214     <comment>(Select at least one of the HCDs. If you are unsure, picking all is fine.)</comment>
215 neysx 1.3 --- USB Host Controller Drivers
216 swift 1.1 &lt;*&gt; EHCI HCD (USB 2.0) support
217     &lt; &gt; OHCI HCD support
218     &lt;*&gt; UHCI HCD (most Intel and VIA) support
219    
220     <comment>(Moving a little further down, we come to CDC and mass storage.)</comment>
221     &lt; &gt; USB Modem (CDC ACM) support
222     &lt;*&gt; USB Printer support
223     &lt;*&gt; USB Mass Storage support
224    
225     <comment>(If you have a USB Network Card like the RTL8150, you'll need this)</comment>
226     USB Network Adapters --->
227     &lt;*&gt; USB RTL8150 based ethernet device support (EXPERIMENTAL)
228    
229     <comment>(If you have a serial to USB converter like the Prolific 2303, you'll need this)</comment>
230     USB Serial Converter support --->
231     &lt;*&gt; USB Serial Converter support
232 neysx 1.3 &lt;*&gt; USB Prolific 2303 Single Port Serial Driver (NEW)
233 swift 1.1 </pre>
234    
235     <p>
236 nightmorph 1.18 If you have a USB keyboard, mouse, joystick, or any other input device, you need
237     to enable HID support. Go back one level to "Device drivers" and enable HID
238     support as shown:
239 swift 1.1 </p>
240 neysx 1.3
241 nightmorph 1.18 <pre caption="Enabling HID support">
242     Device Drivers ---&gt;
243     [*] HID Devices ---&gt;
244     &lt;*&gt; USB Human Interface Device (full HID) support
245 swift 1.1 </pre>
246    
247     <p>
248 nightmorph 1.18 Now that your options are set, you can (re)compile the kernel and USB support
249     should be functional once you reboot into the new kernel. You can now proceed
250     to <uri link="#postkern">Seeing USB at work</uri> and see if everything is
251     working as it should.
252 swift 1.1 </p>
253 neysx 1.3
254 swift 1.1 </body>
255     </section>
256     </chapter>
257    
258     <chapter id="postkern">
259     <title>Seeing USB at work</title>
260     <section>
261     <title>dmesg is your friend!</title>
262     <body>
263    
264     <p>
265 neysx 1.3 The time has finally come to play with those USB devices :) So let's get
266     started. In this chapter, we'll see how the system responds to various USB
267     devices. We'll start by plugging in a USB 512 MB Memory Stick/Pen Drive. You
268     could use some other similar mass storage device. We will primarily use
269     <c>dmesg</c> to see what is happening and how the system responds to the
270 swift 1.1 device.
271     </p>
272    
273     <note>
274 neysx 1.3 <c>dmesg</c> will generally give a lot of output up front before coming to the
275 swift 1.1 info we need, as it reads the kernel ring buffer that has all the boot up
276 neysx 1.3 messages as well. The output in the following examples have only the relevant
277     portion(s) and extra spaces in between to enable better readability. If needed
278     please use a <c>dmesg | more</c> or <c>dmesg | less</c> to see the output
279 yoswink 1.2 better in your system.
280 swift 1.1 </note>
281    
282     <pre caption="dmesg output for Memory Stick">
283     <comment>(Plug in Memory Stick into available USB port and then..)</comment>
284 yoswink 1.2 # <i>dmesg | less</i>
285 swift 1.1
286 neysx 1.3 <comment>(The device is picked up as a USB 1.1 and allocated an address.
287     Also says what HCD it is using.)</comment>
288 swift 1.1 usb 1-1: new full speed USB device using uhci_hcd and address 2
289    
290     <comment>(SCSI emulation automatically kicks in)</comment>
291     scsi0 : SCSI emulation for USB Mass Storage devices
292     usb-storage: device found at 2
293    
294     <comment>(Now the device information including model number is retrieved)</comment>
295     usb-storage: waiting for device to settle before scanning
296     Vendor: JetFlash Model: TS512MJF2A Rev: 1.00
297     Type: Direct-Access ANSI SCSI revision: 02
298     SCSI device sda: 1003600 512-byte hdwr sectors (514 MB)
299    
300     <comment>(The write-protect sense is EXPERIMENTAL code in the later kernels)</comment>
301     sda: Write Protect is off
302     sda: Mode Sense: 0b 00 00 08
303     sda: assuming drive cache: write through
304     SCSI device sda: 1003600 512-byte hdwr sectors (514 MB)
305     /dev/scsi/host0/bus0/target0/lun0: p1
306     Attached scsi removable disk sda at scsi0, channel 0, id 0, lun 0
307     Attached scsi generic sg0 at scsi0, channel 0, id 0, lun 0, type 0
308     usb-storage: device scan complete
309     <comment>(At this point, the device is generally accessible by mounting /dev/sda1)</comment>
310    
311     <comment>(When the device is disconnected, the system acknowledges the same)</comment>
312     usb 1-1: USB disconnect, address 2
313     </pre>
314    
315     <p>
316 neysx 1.3 Once the device is connected and mounted, you can access it like a normal hard
317 swift 1.6 disk. Usual operations like <c>cp</c>, <c>mv</c>, <c>rm</c>, etc work fine. You
318 swift 1.1 could also create a filesystem on the USB stick/format it.
319     </p>
320    
321     <pre caption="Accessing the Memory Stick">
322     # <i>mount /dev/sda1 /mnt/usb</i>
323     # <i>df -h</i>
324     Filesystem Size Used Avail Use% Mounted on
325     /dev/hda8 9.4G 7.5G 1.9G 80% /
326     /dev/hda9 11G 8.1G 2.4G 78% /usr
327     none 189M 0 189M 0% /dev/shm
328     /dev/sda1 490M 34M 457M 7% /mnt/usb
329     </pre>
330    
331     <note>
332 neysx 1.3 Digital cameras can be accessed the same way as memory sticks. I have a Nikon
333 fox2mike 1.7 Coolpix 5200 and this is the way I access it. Cameras these days usually have
334     two modes to transfer pictures; USB mass storage and PTP (Picture Transfer
335     Protocol). The camera is set to USB mass storage mode and hence the procedure is
336     exactly the same as that of accessing a memory stick because of which I have not
337     explained in detail about it. Please note that this may NOT work in all cases
338     and with all digital cameras that have USB support.
339 swift 1.1 </note>
340    
341     <p>
342 neysx 1.3 How would a USB mouse show up in case you had one? It will show up as an HID
343 swift 1.1 device.
344     </p>
345    
346     <pre caption="USB Optical Mouse">
347     # <i>dmesg | grep USB</i>
348     drivers/usb/input/hid-core.c: v2.0:USB HID core driver
349     usb 1-1: new low speed USB device using address 2
350     input: USB HID v1.10 Mouse [Logitech USB-PS/2 Optical Mouse] on usb-0000:00:07.2-1
351     </pre>
352    
353     <p>
354 neysx 1.3 Another nifty command you can use to see the status of your USB ports is
355     <c>lsusb</c>. This is part of <c>sys-apps/usbutils</c> and will be covered in
356 swift 1.1 the next chapter.
357     </p>
358    
359     </body>
360     </section>
361     </chapter>
362    
363     <chapter>
364     <title>Userspace USB</title>
365     <section>
366     <title>Nifty tools</title>
367     <body>
368    
369     <p>
370 neysx 1.3 So far we've seen how much support exists on the kernel/system side for USB on
371     Linux. Now we'll take a peek into what kind of support is provided by Gentoo
372 swift 1.1 for USB in the userspace.
373     </p>
374    
375     <p>
376 neysx 1.3 One of the most useful tools around is <c>lsusb</c>. This lists all the usb
377 swift 1.1 devices connected to the system. Installing it is a breeze.
378     </p>
379    
380     <pre caption="Installing usbutils">
381     # <i>emerge usbutils</i>
382     </pre>
383    
384     <p>
385 neysx 1.3 Once installed, you can just run <c>lsusb</c> to get simple info on the USB
386 swift 1.1 devices attached to the machine.
387     </p>
388    
389     <note>
390     You have to be root in most cases to run <c>lsusb</c>.
391     </note>
392    
393     <warn>
394 neysx 1.3 <c>lsusb</c> reads the information for the USB devices from
395     <path>/proc/bus/usb</path>. If you have not enabled that in your kernel,
396     chances are that <c>lsusb</c> may not work at all. Please ensure you have
397 swift 1.1 <path>/proc</path> filesystem support enabled in your kernel and that
398     <c>usbfs</c> is mounted at <path>/proc/bus/usb</path> (which should happen
399     automatically).
400     </warn>
401    
402     <pre caption="lsusb at work">
403     # <i>lsusb</i>
404     <comment>(This is the 512 MB Memory Stick from Transcend)</comment>
405     Bus 001 Device 003: ID 0c76:0005 JMTek, LLC. USBdisk
406     <comment>(This is the Optical Mouse)</comment>
407     Bus 001 Device 002: ID 046d:c00e Logitech, Inc. Optical Mouse
408     <comment>(This is the root hub)</comment>
409     Bus 001 Device 001: ID 0000:0000
410     </pre>
411    
412     <p>
413 neysx 1.3 If you are one of those types who love to see lots of information, you have
414     the option of running <c>lsusb -v</c>. Try that and see the amount of info it
415     gives out. Another good option is that <c>lsusb</c> dumps the current physical
416     USB hierarchy as a tree and thus makes it easier to understand the exact
417 swift 1.1 device map. The command is <c>lsusb -t</c>. For example,
418     </p>
419    
420     <pre caption="lsusb showing USB hierarchy">
421     # <i>lsusb -t</i>
422     Bus# 1
423     `-Dev# 1 Vendor 0x0000 Product 0x0000
424     |-Dev# 2 Vendor 0x046d Product 0xc00e
425     `-Dev# 3 Vendor 0x0c76 Product 0x0005
426     </pre>
427    
428     <p>
429 neysx 1.3 You can easily correlate the outputs of <c>lsusb</c> and <c>lsusb -t</c>,
430 swift 1.1 which helps debugging as well as understanding how USB works.
431     </p>
432    
433     </body>
434     </section>
435     </chapter>
436    
437     <chapter>
438     <title>And thanks to...</title>
439     <section>
440     <title>References</title>
441     <body>
442    
443     <p>
444 swift 1.6 A good number of online documents helped me during the development of this
445 swift 1.17 document and there are some that are highly technical but truly interesting.
446 swift 1.6 I thought they all deserve some credit, so here we go!
447 swift 1.1 </p>
448 neysx 1.3
449     <ul>
450     <li><uri link="http://www.usb.org">The Official USB Website</uri></li>
451 swift 1.8 <li><uri link="http://www.usb.org/about/faq">The USB FAQ</uri></li>
452 neysx 1.3 <li>
453     <uri
454     link="http://h18000.www1.hp.com/productinfo/development/openhci.html">Compaq's
455     OHCI Standard</uri>
456     </li>
457     <li>
458     <uri link="http://developer.intel.com/technology/usb/uhci11d.htm">Intel's
459     UHCI Standard</uri>
460     </li>
461     <li>
462     <uri link="http://www.intel.com/technology/usb/ehcispec.htm">Intel's EHCI
463     Standard</uri>
464     </li>
465 fox2mike 1.10 </ul>
466    
467     </body>
468     </section>
469     <section>
470     <title>Other Interesting Links</title>
471     <body>
472    
473     <ul>
474 swift 1.17 <li><uri link="/doc/en/liveusb.xml">Gentoo Linux LiveUSB HOWTO</uri></li>
475 neysx 1.3 </ul>
476 swift 1.1
477     </body>
478     </section>
479     </chapter>
480     </guide>

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