On Wed, 2007-05-02 at 22:30 -0700, Greg KH wrote: > > Hide the config menu for userspace I/O on s390. > > Why? Who says s390 can't have userspace I/O drivers someday?
Theoretically yes, but in practice this is very unlikely to happen. Some reasons why: 1) There are only very few device drivers for s390, the few we need we'll do as kernel space drivers 2) The irq abstraction of uio is awkward. The irq handler uses a 32-bit integer. On s390 each ccw device has it's own irq and ccw devices are identified with a string "x.y.zzzz". Then there are devices that deliver external interrupts where a 16-bit number is used to identify the source. You could invent some mapping logic of a 32 bit integer to all the possible interrupt sources but it doesn't really match. 3) s390 doesn't use memory mapped i/o, you always need to execute a privileged instruction to trigger activity on the device, e.g. ssch for a ccw device, siga for qdio, nqap for crypto, ... So I have my doubts that we will ever see a uio driver for s390. If we do we can unhide the config menu again. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
