virtio: Formally reserve bits 24-31 to be 'transport' features. We assign feature bits as required, but it makes sense to reserve some for the particular transport, rather than the particular device. Signed-off-by: Rusty Russell --- drivers/virtio/virtio.c | 5 +++++ include/linux/virtio_config.h | 7 +++++++ 2 files changed, 12 insertions(+) diff -r 8b365338fbbf drivers/virtio/virtio.c --- a/drivers/virtio/virtio.c Tue Apr 22 13:21:34 2008 +1000 +++ b/drivers/virtio/virtio.c Tue Apr 22 13:48:58 2008 +1000 @@ -117,6 +117,11 @@ static int virtio_dev_probe(struct devic set_bit(f, dev->features); } + /* Transport features are always preserved to pass to set_features. */ + for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++) + if (device_features & (1 << i)) + set_bit(i, dev->features); + err = drv->probe(dev); if (err) add_status(dev, VIRTIO_CONFIG_S_FAILED); diff -r 8b365338fbbf include/linux/virtio_config.h --- a/include/linux/virtio_config.h Tue Apr 22 13:21:34 2008 +1000 +++ b/include/linux/virtio_config.h Tue Apr 22 13:48:58 2008 +1000 @@ -14,6 +14,13 @@ #define VIRTIO_CONFIG_S_DRIVER_OK 4 /* We've given up on this device. */ #define VIRTIO_CONFIG_S_FAILED 0x80 + +/* Some virtio feature bits (currently bits 24 through 31) are reserved for the + * transport being used (eg. virtio_ring), the rest are per-device feature + * bits. */ +#define VIRTIO_TRANSPORT_F_START 24 +#define VIRTIO_TRANSPORT_F_END 32 +#define VIRTIO_TRANSPORT_F_MASK 0xFF000000 #ifdef __KERNEL__ #include