diff options
author | Rusty Russell <rusty@rustcorp.com.au> | 2008-05-02 21:50:50 -0500 |
---|---|---|
committer | Rusty Russell <rusty@rustcorp.com.au> | 2008-05-02 21:50:50 +1000 |
commit | c45a6816c19dee67b8f725e6646d428901a6dc24 (patch) | |
tree | 096e3263fd14e140685bcc3082394ff15f5aeddb /include/linux/virtio.h | |
parent | 72e61eb40b55dd57031ec5971e810649f82b0259 (diff) | |
download | linux-stable-c45a6816c19dee67b8f725e6646d428901a6dc24.tar.gz linux-stable-c45a6816c19dee67b8f725e6646d428901a6dc24.tar.bz2 linux-stable-c45a6816c19dee67b8f725e6646d428901a6dc24.zip |
virtio: explicit advertisement of driver features
A recent proposed feature addition to the virtio block driver revealed
some flaws in the API: in particular, we assume that feature
negotiation is complete once a driver's probe function returns.
There is nothing in the API to require this, however, and even I
didn't notice when it was violated.
So instead, we require the driver to specify what features it supports
in a table, we can then move the feature negotiation into the virtio
core. The intersection of device and driver features are presented in
a new 'features' bitmap in the struct virtio_device.
Note that this highlights the difference between Linux unsigned-long
bitmaps where each unsigned long is in native endian, and a
straight-forward little-endian array of bytes.
Drivers can still remove feature bits in their probe routine if they
really have to.
API changes:
- dev->config->feature() no longer gets and acks a feature.
- drivers should advertise their features in the 'feature_table' field
- use virtio_has_feature() for extra sanity when checking feature bits
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Diffstat (limited to 'include/linux/virtio.h')
-rw-r--r-- | include/linux/virtio.h | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/include/linux/virtio.h b/include/linux/virtio.h index e7d10845b3c1..06005fa9e982 100644 --- a/include/linux/virtio.h +++ b/include/linux/virtio.h @@ -76,6 +76,7 @@ struct virtqueue_ops { * @dev: underlying device. * @id: the device type identification (used to match it with a driver). * @config: the configuration ops for this device. + * @features: the features supported by both driver and device. * @priv: private pointer for the driver's use. */ struct virtio_device @@ -84,6 +85,8 @@ struct virtio_device struct device dev; struct virtio_device_id id; struct virtio_config_ops *config; + /* Note that this is a Linux set_bit-style bitmap. */ + unsigned long features[1]; void *priv; }; @@ -94,6 +97,8 @@ void unregister_virtio_device(struct virtio_device *dev); * virtio_driver - operations for a virtio I/O driver * @driver: underlying device driver (populate name and owner). * @id_table: the ids serviced by this driver. + * @feature_table: an array of feature numbers supported by this device. + * @feature_table_size: number of entries in the feature table array. * @probe: the function to call when a device is found. Returns a token for * remove, or PTR_ERR(). * @remove: the function when a device is removed. @@ -103,6 +108,8 @@ void unregister_virtio_device(struct virtio_device *dev); struct virtio_driver { struct device_driver driver; const struct virtio_device_id *id_table; + const unsigned int *feature_table; + unsigned int feature_table_size; int (*probe)(struct virtio_device *dev); void (*remove)(struct virtio_device *dev); void (*config_changed)(struct virtio_device *dev); |