On Tue, Oct 01, 2013 at 08:35:56PM -0600, Alex Williamson wrote: > On Wed, 2013-10-02 at 02:53 +0100, Christoffer Dall wrote: > > On Tue, Oct 01, 2013 at 05:02:44PM -0500, Kim Phillips wrote: > > > On Tue, 1 Oct 2013 13:00:54 -0700 > > > Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > > > On Tue, Oct 01, 2013 at 01:38:31PM -0500, Kim Phillips wrote: > > > > > Hi, > > > > > > > > > > Santosh and I are having a problem figuring out how to enable binding > > > > > (and re-binding) platform devices to a platform VFIO driver (see > > > > > Antonis' WIP: [1]) in an upstream-acceptable manner. > > > > > > > > > > Binding platform drivers currently depends on a string match in the > > > > > device node's compatible entry. On an arndale, one can currently > > > > > rebind the same device to the same driver like so: > > > > > > > > > > echo 12ce0000.i2c > /sys/bus/platform/drivers/s3c-i2c/12ce0000.i2c/driver/unbind > > > > > echo 12ce0000.i2c > /sys/bus/platform/drivers/s3c-i2c/bind > > > > > > > > > > And one can bind it to the vfio-dt driver, as Antonis instructs, by > > > > > appending a 'vfio-dt' string to the device tree compatible entry for > > > > > the device. Then this would work: > > > > > > > > > > echo 12ce0000.i2c > /sys/bus/platform/drivers/s3c-i2c/12ce0000.i2c/driver/unbind > > > > > echo 12ce0000.i2c > /sys/bus/platform/drivers/vfio-dt/bind > > > > > > > > > > Consequently, the hack patch below [2] allows any platform device to be > > > > > bound to the vfio-dt driver, without making changes to the device > > > > > tree. It's a hack because I don't see having any driver name specific > > > > > code in drivers/base/bus.c being upstream acceptable. > > > > > > > > You are correct. > > > > > > > > What is wrong with just doing the above unbind/bind things through > > > > sysfs, that is what it is there for, right? > > > > > > The bind fails because the compatible string in the device tree doesn't > > > match that of the VFIO platform driver, so driver_match_device always > > > returns false. > > > > > It sounds like this is not going to be pretty almost no matter what > > we'll end up doing: Inherently VFIO is going to bind to a device without > > the device tree entry for that device ever saying anything about VFIO. > > > > How is this solved for PCI? Can we use some analogy from that work to > > construct the missing piece? > > PCI supports a dynamic ID table for driver/device matching, see > pci_add_dynid(). The problem is that this gets a little sloppy for the > period where you have multiple drivers that can claim the same device, > especially in the presence of hotplug. Thus the desire to improve the > situation with some kind of direct binding interface. Thanks, > So that's called on the vfio pci driver? Wouldn't a sysfs file to add compatibility strings to the vfio-platform driver make driver_match_device return true and make everyone happy? There would be an issue of binding priority to solve, I guess similar to the PCI problem, but then at least the two device types would share a common orthogonal challenge. -Christoffer -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
