xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

virtio: explicit advertisement of driver features

Browse Source 
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>
This commit is contained in:
Rusty Russell
2008-05-02 21:50:50 -05:00
parent 72e61eb40b
commit c45a6816c1
8 changed files with 138 additions and 49 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
include/linux/virtio.h
View File

@@ -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);