On Tue, 8 Jul 2003 [EMAIL PROTECTED] wrote: > Hello all, > > I'm setting up a device driver for a GPIB (IEEE-488) interface. GPIB > is a General-Purpose Interface Bus (hence the name) which enables > connection of arbitrary peripherals to a PC. It's used primarily to > support automated test facilities in manufacturing environments. > > Each interface can support up to 30 peripheral devices (hard limit > per the GPIB spec), which can include hard drives, keyboards, > printers, etc. My design will support up to eight interfaces > (arbitrary limit). > > I need to map peripherals to user-visible nodes like /dev/prn0 or > /dev/usb/prn0. I don't know how to register the driver for these > nodes since the configuration is defined by user software. The only > access to the driver from user space appears to be through the open() > or ioctl() functions, but the driver must already be registered for a > node before being called. Seems to be a chicken-and-egg problem ??? > > Also, these mappings must persist through unplugging and replugging > of interfaces, regardless of the order in which this is done, since > the external bus is hard-wired. > > Any help would be much appreciated. > > Leigh Bassett
While it's true that the driver has to be registered for _something_ before it can be called from userspace, that something needn't be one of the devices it controls. For example, you could create an entry under /proc or /sys (for Linux 2.5) and use that to manage the driver. You could even get a miscellaneous char device number assigned to your driver and devote that to its management. That would take care of the chicken-and-egg problem. For the mappings to persist through plugging and unplugging of interfaces, you must have some way for the driver to distinguish one interface from another. Otherwise how could you tell which mapping to install when an interface is plugged in? Under the assumption that this isn't a problem, the mapping information has to be available to a user process which can inform your driver at the appropriate times. For example, you could have a peripheral device management program which would store the configurations in a file, and a hotplug script could read and transmit the file to the driver each time an interface is attached. I hope this is the sort of thing you're looking for... 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
