Hi Greg, On Wed, May 13, 2015 at 08:37:40AM -0700, Greg Kroah-Hartman wrote: > On Wed, May 13, 2015 at 12:26:04PM +0100, Mark Brown wrote: > > On Tue, May 12, 2015 at 10:33:24PM +0200, Maxime Ripard wrote: > > > > > While this is nicer than the DT solution because of its accurate hardware > > > representation, it's still not perfect because you might not have access > > > to the > > > DT, or you might be driving a completely generic device (such as a > > > microcontroller) that might be used for something else in a different > > > context/board. > > > > Greg, you're copied on this because this seems to be a generic problem > > that should perhaps be solved at a driver model level - having a way to > > bind userspace access to devices that we don't otherwise have a driver > > for. The subsystem could specify the UIO driver to use when no other > > driver is available. > > That doesn't really work. I've been talking to the ACPI people about > this, and the problem is "don't otherwise have a driver for" is an > impossible thing to prove, as you never know when a driver is going to > be loaded from userspace. > > You can easily bind drivers to devices today from userspace, why not > just use the built-in functionality you have today if you "know" that > there is no driver for this hardware.
What we're really after here is that we want to have an spidev instance when we don't even have a device. And since SPI isn't really doing any kind of hotplug, the only situation that might be problematic is if we have the DT overlays registering new devices. Maxime -- Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com
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