[3587f7f] | 1 | Version 2009-08-22
|
---|
| 2 |
|
---|
| 3 | ==========================
|
---|
| 4 | WHY DO WE NEED THESE IDs?
|
---|
| 5 | ==========================
|
---|
| 6 |
|
---|
| 7 | USB is more than a low level protocol for data transport. It also defines a
|
---|
| 8 | common set of requests which must be understood by all devices. And as part
|
---|
| 9 | of these common requests, the specification defines data structures, the
|
---|
| 10 | USB Descriptors, which are used to describe the properties of the device.
|
---|
| 11 |
|
---|
| 12 | From the perspective of an operating system, it is therefore possible to find
|
---|
| 13 | out basic properties of a device (such as e.g. the manufacturer and the name
|
---|
| 14 | of the device) without a device-specific driver. This is essential because
|
---|
| 15 | the operating system can choose a driver to load based on this information
|
---|
| 16 | (Plug-And-Play).
|
---|
| 17 |
|
---|
| 18 | Among the most important properties in the Device Descriptor are the USB
|
---|
| 19 | Vendor- and Product-ID. Both are 16 bit integers. The most simple form of
|
---|
| 20 | driver matching is based on these IDs. The driver announces the Vendor- and
|
---|
| 21 | Product-IDs of the devices it can handle and the operating system loads the
|
---|
| 22 | appropriate driver when the device is connected.
|
---|
| 23 |
|
---|
| 24 | It is obvious that this technique only works if the pair Vendor- plus
|
---|
| 25 | Product-ID is unique: Only devices which require the same driver can have the
|
---|
| 26 | same pair of IDs.
|
---|
| 27 |
|
---|
| 28 |
|
---|
| 29 | =====================================================
|
---|
| 30 | HOW DOES THE USB STANDARD ENSURE THAT IDs ARE UNIQUE?
|
---|
| 31 | =====================================================
|
---|
| 32 |
|
---|
| 33 | Since it is so important that USB IDs are unique, the USB Implementers Forum,
|
---|
| 34 | Inc. (usb.org) needs a way to enforce this legally. It is not forbidden by
|
---|
| 35 | law to build a device and assign it any random numbers as IDs. Usb.org
|
---|
| 36 | therefore needs an agreement to regulate the use of USB IDs. The agreement
|
---|
| 37 | binds only parties who agreed to it, of course. Everybody else is free to use
|
---|
| 38 | any numbers for their IDs.
|
---|
| 39 |
|
---|
| 40 | So how can usb.org ensure that every manufacturer of USB devices enters into
|
---|
| 41 | an agreement with them? They do it via trademark licensing. Usb.org has
|
---|
| 42 | registered the trademark "USB", all associated logos and related terms. If
|
---|
| 43 | you want to put an USB logo on your product or claim that it is USB
|
---|
| 44 | compliant, you must license these trademarks from usb.org. And this is where
|
---|
| 45 | you enter into an agreement. See the "USB-IF Trademark License Agreement and
|
---|
| 46 | Usage Guidelines for the USB-IF Logo" at
|
---|
| 47 | http://www.usb.org/developers/logo_license/.
|
---|
| 48 |
|
---|
| 49 | Licensing the USB trademarks requires that you buy a USB Vendor-ID from
|
---|
| 50 | usb.org (one-time fee of ca. 2,000 USD), that you become a member of usb.org
|
---|
| 51 | (yearly fee of ca. 4,000 USD) and that you meet all the technical
|
---|
| 52 | specifications from the USB spec.
|
---|
| 53 |
|
---|
| 54 | This means that most hobbyists and small companies will never be able to
|
---|
| 55 | become USB compliant, just because membership is so expensive. And you can't
|
---|
| 56 | be compliant with a driver based on V-USB anyway, because the AVR's port pins
|
---|
| 57 | don't meet the electrical specifications for USB. So, in principle, all
|
---|
| 58 | hobbyists and small companies are free to choose any random numbers for their
|
---|
| 59 | IDs. They have nothing to lose...
|
---|
| 60 |
|
---|
| 61 | There is one exception worth noting, though: If you use a sub-component which
|
---|
| 62 | implements USB, the vendor of the sub-components may guarantee USB
|
---|
| 63 | compliance. This might apply to some or all of FTDI's solutions.
|
---|
| 64 |
|
---|
| 65 |
|
---|
| 66 | =======================================================================
|
---|
| 67 | WHY SHOULD YOU OBTAIN USB IDs EVEN IF YOU DON'T LICENSE USB TRADEMARKS?
|
---|
| 68 | =======================================================================
|
---|
| 69 |
|
---|
| 70 | You have learned in the previous section that you are free to choose any
|
---|
| 71 | numbers for your IDs anyway. So why not do exactly this? There is still the
|
---|
| 72 | technical issue. If you choose IDs which are already in use by somebody else,
|
---|
| 73 | operating systems will load the wrong drivers and your device won't work.
|
---|
| 74 | Even if you choose IDs which are not currently in use, they may be in use in
|
---|
| 75 | the next version of the operating system or even after an automatic update.
|
---|
| 76 |
|
---|
| 77 | So what you need is a pair of Vendor- and Product-IDs for which you have the
|
---|
| 78 | guarantee that no USB compliant product uses them. This implies that no
|
---|
| 79 | operating system will ever ship with drivers responsible for these IDs.
|
---|
| 80 |
|
---|
| 81 |
|
---|
| 82 | ==============================================
|
---|
| 83 | HOW DOES OBJECTIVE DEVELOPMENT HANDLE USB IDs?
|
---|
| 84 | ==============================================
|
---|
| 85 |
|
---|
| 86 | Objective Development gives away pairs of USB-IDs with their V-USB licenses.
|
---|
| 87 | In order to ensure that these IDs are unique, Objective Development has an
|
---|
| 88 | agreement with the company/person who has bought the USB Vendor-ID from
|
---|
| 89 | usb.org. This agreement ensures that a range of USB Product-IDs is reserved
|
---|
| 90 | for assignment by Objective Development and that the owner of the Vendor-ID
|
---|
| 91 | won't give it to anybody else.
|
---|
| 92 |
|
---|
| 93 | This means that you have to trust three parties to ensure uniqueness of
|
---|
| 94 | your IDs:
|
---|
| 95 |
|
---|
| 96 | - Objective Development, that they don't give the same PID to more than
|
---|
| 97 | one person.
|
---|
| 98 | - The owner of the Vendor-ID that they don't assign PIDs from the range
|
---|
| 99 | assigned to Objective Development to anybody else.
|
---|
| 100 | - Usb.org that they don't assign the same Vendor-ID a second time.
|
---|
| 101 |
|
---|
| 102 |
|
---|
| 103 | ==================================
|
---|
| 104 | WHO IS THE OWNER OF THE VENDOR-ID?
|
---|
| 105 | ==================================
|
---|
| 106 |
|
---|
| 107 | Objective Development has obtained ranges of USB Product-IDs under two
|
---|
| 108 | Vendor-IDs: Under Vendor-ID 5824 from Wouter van Ooijen (Van Ooijen
|
---|
| 109 | Technische Informatica, www.voti.nl) and under Vendor-ID 8352 from Jason
|
---|
| 110 | Kotzin (Clay Logic, www.claylogic.com). Both VID owners have received their
|
---|
| 111 | Vendor-ID directly from usb.org.
|
---|
| 112 |
|
---|
| 113 |
|
---|
| 114 | =========================================================================
|
---|
| 115 | CAN I USE USB-IDs FROM OBJECTIVE DEVELOPMENT WITH OTHER DRIVERS/HARDWARE?
|
---|
| 116 | =========================================================================
|
---|
| 117 |
|
---|
| 118 | The short answer is: Yes. All you get is a guarantee that the IDs are never
|
---|
| 119 | assigned to anybody else. What more do you need?
|
---|
| 120 |
|
---|
| 121 |
|
---|
| 122 | ============================
|
---|
| 123 | WHAT ABOUT SHARED ID PAIRS?
|
---|
| 124 | ============================
|
---|
| 125 |
|
---|
| 126 | Objective Development has reserved some PID/VID pairs for shared use. You
|
---|
| 127 | have no guarantee of uniqueness for them, except that no USB compliant device
|
---|
| 128 | uses them. In order to avoid technical problems, we must ensure that all
|
---|
| 129 | devices with the same pair of IDs use the same driver on kernel level. For
|
---|
| 130 | details, see the file USB-IDs-for-free.txt.
|
---|
| 131 |
|
---|
| 132 |
|
---|
| 133 | ======================================================
|
---|
| 134 | I HAVE HEARD THAT SUB-LICENSING OF USB-IDs IS ILLEGAL?
|
---|
| 135 | ======================================================
|
---|
| 136 |
|
---|
| 137 | A 16 bit integer number cannot be protected by copyright laws. It is not
|
---|
| 138 | sufficiently complex. And since none of the parties involved entered into the
|
---|
| 139 | USB-IF Trademark License Agreement, we are not bound by this agreement. So
|
---|
| 140 | there is no reason why it should be illegal to sub-license USB-IDs.
|
---|
| 141 |
|
---|
| 142 |
|
---|
| 143 | =============================================
|
---|
| 144 | WHO IS LIABLE IF THERE ARE INCOMPATIBILITIES?
|
---|
| 145 | =============================================
|
---|
| 146 |
|
---|
| 147 | Objective Development disclaims all liabilities which might arise from the
|
---|
| 148 | assignment of IDs. If you guarantee product features to your customers
|
---|
| 149 | without proper disclaimer, YOU are liable for that.
|
---|