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diff --git a/usbdrv/USB-ID-FAQ.txt b/usbdrv/USB-ID-FAQ.txt new file mode 100644 index 0000000..a4a6bd6 --- /dev/null +++ b/usbdrv/USB-ID-FAQ.txt @@ -0,0 +1,149 @@ +Version 2012-07-09 + +========================== +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 (now flirc.tv, Inc.). 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. |