> > Don't drag USB into this. There's no reason to specify how the
> > bus is connected to the host. The cleanest way to do this is to get a
> > GPIB major number.
> >
>
> That seems like a cleaner way to do it. Hide the USB connectivity
> from the user. But there's still the problem of hotplugging.
That's not confined to USB. These days PCI is hotpluggable as well.
> > > 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 ???
> >
> > If you wish to export all a bus's devices to user space, you might
> > just as well register 2**5 devices per GPIB bus. Could you state your
> > problem more clearly?
> >
>
> Clarity is actually the essence of the problem. Each system will be
> different, and each user will likely have many different system
> configurations, which could change many times per day. I have no
> control over the configuration. I have to support whatever the
> client chooses to define.
What do you need?
A full support of all features and devices of GPIB is about as complex
as the whole SCSI layer.
The simplest option is representing the whole bus as one device.
That's the conventional and easy solution.
It has some obvious drawbacks:
1. Essentially single user operation
2. Some devices need kernel drivers (disks, keyboards, ...)
If you can live with representing any device on the bus as a device
you can register a device for each address possible on GPIB and get
away with a thin generic layer doing TALK/LISTEN and handle SRQ
If you need to represent several kinds of devices as several kinds
of device nodes, you have a problem. You basically need to write
a GPIB subsystem, in which the driver for your physical device would
be in the same role as for example the OHCI driver is to USB in general.
> > > 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.
> >
> > Almost impossible unless you can tell GPIB adapters apart.
> >
>
> I can identify them by serial number.
Export it and leave the rest to hotplug scripts.
A few symlinks can fix the problem.
Regards
Oliver
-------------------------------------------------------
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
