From dd7c7bc46211785a1aa7d70feb15830f62682b3c Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Fri, 25 Jul 2008 12:06:07 -0500 Subject: [PATCH] virtio: Formally reserve bits 28-31 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 | 6 ++++++ 2 files changed, 11 insertions(+) diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c index fc85cba64578..baf103361e3a 100644 --- a/drivers/virtio/virtio.c +++ b/drivers/virtio/virtio.c @@ -113,6 +113,11 @@ static int virtio_dev_probe(struct device *_d) 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 --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h index 7eb4b34d13bb..5a30cfb7934b 100644 --- a/include/linux/virtio_config.h +++ b/include/linux/virtio_config.h @@ -18,6 +18,12 @@ /* We've given up on this device. */ #define VIRTIO_CONFIG_S_FAILED 0x80 +/* Some virtio feature bits (currently bits 28 through 31) are reserved for the + * transport being used (eg. virtio_ring), the rest are per-device feature + * bits. */ +#define VIRTIO_TRANSPORT_F_START 28 +#define VIRTIO_TRANSPORT_F_END 32 + /* Do we get callbacks when the ring is completely used, even if we've * suppressed them? */ #define VIRTIO_F_NOTIFY_ON_EMPTY 24