On Tue, 8 Jul 2003 [EMAIL PROTECTED] wrote: > Hi Alan, > > Thanks for the quick response. > > Right now I'm setting up one device per interface (using my company > name ATS) at /dev/usb/ats[0-7]. This gives me access to the base > device in the interface. I'm currently using the USB major (180) and > minors 128-135. > > How would I get a miscellaneous character device major assigned? > That seems the appropriate method, since the entire GPIB system could > support 256 peripherals. (Actually many more since there is a sub- > addressing mechanism that supports 256 logical devices at each > physical GPIB address, so 64K devices is the theoretical maximum).
See Documentation/devices.txt. But do you really need all these device numbers? Consider using devfs, which does dynamic device number assignment. > I hadn't considered using the hotplug script mechanism for > configuring the system, but it might be appropriate. The system > configuration actually changes depending on what user program is > running at the time, with some devices being ignored and other bus > addresses being reused by different devices. For example you could > disconnect a DVM (/dev/usb/dvm0) at GPIB address 17 and connect a > printer (/dev/usb/prn0) at GPIB address 17, then run the program that > understands that topology. This particular program would never > access /dev/usb/dvm0 even though that device was defined in the > overall system. That sounds confusing. Does it mean that /dev/usb/dvm0 and /dev/usb/prn0 would contain the same major/minor numbers? And wouldn't these numbers have to change every time you re-wire your GPIB bus? For that matter, how much difference does it make to your driver whether a particular device happens to be a printer rather than a DVM? Wouldn't the driver just transmit data back-and-forth the same, regardless? Maybe you should develop a user library to communicate with your driver. Then any program could easily inform the driver about the devices it's going to use, in an implementation-independent way. Maybe you could write the driver so that it uses a single major/minor combination. Have it require the user program to call a particular ioctl to select a GPIB address before it does anything else to the open file. Then keeping track of the device <-> address mapping becomes purely a userspace problem. > I'm working with the 2.4 kernel as a development platform. Since > this product will go into existing installations, I expect most of > the customers will have that version. I'm hoping I don't have to > support 2.2. Support for the 2.6 kernel will be added when it > becomes commercially available. > > Thanks very much for your help. Greatly appreciated. > > Leigh Bassett You're welcome. Alan Stern ------------------------------------------------------- This SF.Net email sponsored by: Parasoft Error proof Web apps, automate testing & more. Download & eval WebKing and get a free book. www.parasoft.com/bulletproofapps _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
