On Fri, Jul 15, 2016 at 10:42:37AM +0900, Greg Kroah-Hartman wrote: > On Thu, Jul 14, 2016 at 08:53:06PM -0400, Rich Felker wrote: > > mmap of uio devices does not seem to work without further > > nommu-specific support, but interrupt handling already works, and > > userspace drivers for nommu systems can simply use physical mmio > > addresses from userspace directly anyway without mmap. > > > > Signed-off-by: Rich Felker <dal...@libc.org> > > --- > > > > I don't particularly expect this to be accepted upstream as-is, but > > since we're actually trying to use the UIO subsystem on nommu (J2), > > I'd like to start a discussion of what an acceptable patch would > > entail. > > > > The uio_pdrv_genirq driver was tested on J2 with this patch and > > interrupt handling works as expected. > > > > drivers/uio/Kconfig | 1 - > > 1 file changed, 1 deletion(-) > > > > diff --git a/drivers/uio/Kconfig b/drivers/uio/Kconfig > > index 52c98ce..387b2bb 100644 > > --- a/drivers/uio/Kconfig > > +++ b/drivers/uio/Kconfig > > @@ -1,6 +1,5 @@ > > menuconfig UIO > > tristate "Userspace I/O drivers" > > - depends on MMU > > This doesn't seem to do much, don't you need to modify uio-specific > drivers? Or given that the core uio code doesn't rely on mmu, is this > safe?
As noted above, mmap of the device does not work (returns error); I don't understand why. But select/read/write for interrupt handling works fine, and the uio system is fully usable if you just do mmio via the raw addresses from userspace (this is nommu after all). I tested it with uio_pdrv_genirq bound to a fake DT node for the J2 IPI interrupt, disabling SMP and generating IPI interrupts manually to check that it worked. Rich
