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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 <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell 2008-07-25 12:06:07 -05:00
parent faeba830b0
commit dd7c7bc462
2 changed files with 11 additions and 0 deletions
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5
drivers/virtio/virtio.c
View File

@ -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);

6
include/linux/virtio_config.h
View File

@ -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