| Version 2009-08-22 |
| |
| ========================== |
| WHY DO WE NEED THESE IDs? |
| ========================== |
| |
| USB is more than a low level protocol for data transport. It also defines a |
| common set of requests which must be understood by all devices. And as part |
| of these common requests, the specification defines data structures, the |
| USB Descriptors, which are used to describe the properties of the device. |
| |
| From the perspective of an operating system, it is therefore possible to find |
| out basic properties of a device (such as e.g. the manufacturer and the name |
| of the device) without a device-specific driver. This is essential because |
| the operating system can choose a driver to load based on this information |
| (Plug-And-Play). |
| |
| Among the most important properties in the Device Descriptor are the USB |
| Vendor- and Product-ID. Both are 16 bit integers. The most simple form of |
| driver matching is based on these IDs. The driver announces the Vendor- and |
| Product-IDs of the devices it can handle and the operating system loads the |
| appropriate driver when the device is connected. |
| |
| It is obvious that this technique only works if the pair Vendor- plus |
| Product-ID is unique: Only devices which require the same driver can have the |
| same pair of IDs. |
| |
| |
| ===================================================== |
| HOW DOES THE USB STANDARD ENSURE THAT IDs ARE UNIQUE? |
| ===================================================== |
| |
| Since it is so important that USB IDs are unique, the USB Implementers Forum, |
| Inc. (usb.org) needs a way to enforce this legally. It is not forbidden by |
| law to build a device and assign it any random numbers as IDs. Usb.org |
| therefore needs an agreement to regulate the use of USB IDs. The agreement |
| binds only parties who agreed to it, of course. Everybody else is free to use |
| any numbers for their IDs. |
| |
| So how can usb.org ensure that every manufacturer of USB devices enters into |
| an agreement with them? They do it via trademark licensing. Usb.org has |
| registered the trademark "USB", all associated logos and related terms. If |
| you want to put an USB logo on your product or claim that it is USB |
| compliant, you must license these trademarks from usb.org. And this is where |
| you enter into an agreement. See the "USB-IF Trademark License Agreement and |
| Usage Guidelines for the USB-IF Logo" at |
| http://www.usb.org/developers/logo_license/. |
| |
| Licensing the USB trademarks requires that you buy a USB Vendor-ID from |
| usb.org (one-time fee of ca. 2,000 USD), that you become a member of usb.org |
| (yearly fee of ca. 4,000 USD) and that you meet all the technical |
| specifications from the USB spec. |
| |
| This means that most hobbyists and small companies will never be able to |
| become USB compliant, just because membership is so expensive. And you can't |
| be compliant with a driver based on V-USB anyway, because the AVR's port pins |
| don't meet the electrical specifications for USB. So, in principle, all |
| hobbyists and small companies are free to choose any random numbers for their |
| IDs. They have nothing to lose... |
| |
| There is one exception worth noting, though: If you use a sub-component which |
| implements USB, the vendor of the sub-components may guarantee USB |
| compliance. This might apply to some or all of FTDI's solutions. |
| |
| |
| ======================================================================= |
| WHY SHOULD YOU OBTAIN USB IDs EVEN IF YOU DON'T LICENSE USB TRADEMARKS? |
| ======================================================================= |
| |
| You have learned in the previous section that you are free to choose any |
| numbers for your IDs anyway. So why not do exactly this? There is still the |
| technical issue. If you choose IDs which are already in use by somebody else, |
| operating systems will load the wrong drivers and your device won't work. |
| Even if you choose IDs which are not currently in use, they may be in use in |
| the next version of the operating system or even after an automatic update. |
| |
| So what you need is a pair of Vendor- and Product-IDs for which you have the |
| guarantee that no USB compliant product uses them. This implies that no |
| operating system will ever ship with drivers responsible for these IDs. |
| |
| |
| ============================================== |
| HOW DOES OBJECTIVE DEVELOPMENT HANDLE USB IDs? |
| ============================================== |
| |
| Objective Development gives away pairs of USB-IDs with their V-USB licenses. |
| In order to ensure that these IDs are unique, Objective Development has an |
| agreement with the company/person who has bought the USB Vendor-ID from |
| usb.org. This agreement ensures that a range of USB Product-IDs is reserved |
| for assignment by Objective Development and that the owner of the Vendor-ID |
| won't give it to anybody else. |
| |
| This means that you have to trust three parties to ensure uniqueness of |
| your IDs: |
| |
| - Objective Development, that they don't give the same PID to more than |
| one person. |
| - The owner of the Vendor-ID that they don't assign PIDs from the range |
| assigned to Objective Development to anybody else. |
| - Usb.org that they don't assign the same Vendor-ID a second time. |
| |
| |
| ================================== |
| WHO IS THE OWNER OF THE VENDOR-ID? |
| ================================== |
| |
| Objective Development has obtained ranges of USB Product-IDs under two |
| Vendor-IDs: Under Vendor-ID 5824 from Wouter van Ooijen (Van Ooijen |
| Technische Informatica, www.voti.nl) and under Vendor-ID 8352 from Jason |
| Kotzin (Clay Logic, www.claylogic.com). Both VID owners have received their |
| Vendor-ID directly from usb.org. |
| |
| |
| ========================================================================= |
| CAN I USE USB-IDs FROM OBJECTIVE DEVELOPMENT WITH OTHER DRIVERS/HARDWARE? |
| ========================================================================= |
| |
| The short answer is: Yes. All you get is a guarantee that the IDs are never |
| assigned to anybody else. What more do you need? |
| |
| |
| ============================ |
| WHAT ABOUT SHARED ID PAIRS? |
| ============================ |
| |
| Objective Development has reserved some PID/VID pairs for shared use. You |
| have no guarantee of uniqueness for them, except that no USB compliant device |
| uses them. In order to avoid technical problems, we must ensure that all |
| devices with the same pair of IDs use the same driver on kernel level. For |
| details, see the file USB-IDs-for-free.txt. |
| |
| |
| ====================================================== |
| I HAVE HEARD THAT SUB-LICENSING OF USB-IDs IS ILLEGAL? |
| ====================================================== |
| |
| A 16 bit integer number cannot be protected by copyright laws. It is not |
| sufficiently complex. And since none of the parties involved entered into the |
| USB-IF Trademark License Agreement, we are not bound by this agreement. So |
| there is no reason why it should be illegal to sub-license USB-IDs. |
| |
| |
| ============================================= |
| WHO IS LIABLE IF THERE ARE INCOMPATIBILITIES? |
| ============================================= |
| |
| Objective Development disclaims all liabilities which might arise from the |
| assignment of IDs. If you guarantee product features to your customers |
| without proper disclaimer, YOU are liable for that. |