Unlike virtio-pci, virtio-ccw is currently always a transitional driver (i.e. it always includes support for legacy devices.) The differences between legacy and virtio-1+ virtio-ccw devices are not that big (the most interesting things are in common virtio code anyway.) It might be beneficial to make support for legacy virtio generally configurable, in case we want to remove it completely in a future where we all have flying cars. As a prereq, we need to make it configurable for virtio-ccw. Patch 1 introduces a parameter; now that I look at it, it's probably not that useful (not even for testing), so I'm inclined to drop it again. Patch 2 adds a new config symbol for generic legacy virtio support, which currently does not do anything but being selected by the legacy options for virtio-pci and virtio-ccw. A virtio-ccw driver without legacy support will require a revision of 1 or higher to be supported by the device. A virtio-ccw driver with legacy turned off works well for me with transitional devices and fails onlining gracefully for legacy devices (max_revision=0 in QEMU). (I also have some code that allows to make devices non-transitional in QEMU, but I haven't yet found time to polish the patches.) Cornelia Huck (2): virtio/s390: add parameter for minimum revision virtio/s390: make legacy support configurable arch/s390/Kconfig | 11 ++ drivers/s390/virtio/Makefile | 1 + drivers/s390/virtio/virtio_ccw.c | 179 ++++++++---------------- drivers/s390/virtio/virtio_ccw_common.h | 113 +++++++++++++++ drivers/s390/virtio/virtio_ccw_legacy.c | 138 ++++++++++++++++++ drivers/virtio/Kconfig | 8 ++ 6 files changed, 330 insertions(+), 120 deletions(-) create mode 100644 drivers/s390/virtio/virtio_ccw_common.h create mode 100644 drivers/s390/virtio/virtio_ccw_legacy.c base-commit: cf6acb8bdb1d829b85a4daa2944bf9e71c93f4b9 -- 2.26.2
