* Cornelia Huck (cohuck@xxxxxxxxxx) wrote: > On Tue, 7 May 2019 15:18:26 -0600 > Alex Williamson <alex.williamson@xxxxxxxxxx> wrote: > > > On Sun, 5 May 2019 21:49:04 -0400 > > Yan Zhao <yan.y.zhao@xxxxxxxxx> wrote: > > > > + Errno: > > > + If vendor driver wants to claim a mdev device incompatible to all other mdev > > > + devices, it should not register version attribute for this mdev device. But if > > > + a vendor driver has already registered version attribute and it wants to claim > > > + a mdev device incompatible to all other mdev devices, it needs to return > > > + -ENODEV on access to this mdev device's version attribute. > > > + If a mdev device is only incompatible to certain mdev devices, write of > > > + incompatible mdev devices's version strings to its version attribute should > > > + return -EINVAL; > > > > I think it's best not to define the specific errno returned for a > > specific situation, let the vendor driver decide, userspace simply > > needs to know that an errno on read indicates the device does not > > support migration version comparison and that an errno on write > > indicates the devices are incompatible or the target doesn't support > > migration versions. > > I think I have to disagree here: It's probably valuable to have an > agreed error for 'cannot migrate at all' vs 'cannot migrate between > those two particular devices'. Userspace might want to do different > things (e.g. trying with different device pairs). Trying to stuff these things down an errno seems a bad idea; we can't get much information that way. Dave -- Dr. David Alan Gilbert / dgilbert@xxxxxxxxxx / Manchester, UK
