virtio: simplify config mechanism.
Previously we used a type/len pair within the config space, but this
seems overkill. We now simply define a structure which represents the
layout in the config space: the config space can now only be extended
at the end.
The main driver-visible changes:
1) We indicate what fields are present with an explicit feature bit.
2) Virtqueues are explicitly numbered, and not in the config space.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index bcc0188..70bb260 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -5,7 +5,7 @@
* store and access that space differently. */
#include <linux/types.h>
-/* Status byte for guest to report progress, and synchronize config. */
+/* Status byte for guest to report progress, and synchronize features. */
/* We have seen device and processed generic fields (VIRTIO_CONFIG_F_VIRTIO) */
#define VIRTIO_CONFIG_S_ACKNOWLEDGE 1
/* We have found a driver for the device. */
@@ -15,34 +15,27 @@
/* We've given up on this device. */
#define VIRTIO_CONFIG_S_FAILED 0x80
-/* Feature byte (actually 7 bits availabe): */
-/* Requirements/features of the virtio implementation. */
-#define VIRTIO_CONFIG_F_VIRTIO 1
-/* Requirements/features of the virtqueue (may have more than one). */
-#define VIRTIO_CONFIG_F_VIRTQUEUE 2
-
#ifdef __KERNEL__
struct virtio_device;
/**
* virtio_config_ops - operations for configuring a virtio device
- * @find: search for the next configuration field of the given type.
+ * @feature: search for a feature in this config
* vdev: the virtio_device
- * type: the feature type
- * len: the (returned) length of the field if found.
- * Returns a token if found, or NULL. Never returnes the same field twice
- * (ie. it's used up).
- * @get: read the value of a configuration field after find().
+ * bit: the feature bit
+ * Returns true if the feature is supported. Acknowledges the feature
+ * so the host can see it.
+ * @get: read the value of a configuration field
* vdev: the virtio_device
- * token: the token returned from find().
+ * offset: the offset of the configuration field
* buf: the buffer to write the field value into.
- * len: the length of the buffer (given by find()).
+ * len: the length of the buffer
* Note that contents are conventionally little-endian.
- * @set: write the value of a configuration field after find().
+ * @set: write the value of a configuration field
* vdev: the virtio_device
- * token: the token returned from find().
+ * offset: the offset of the configuration field
* buf: the buffer to read the field value from.
- * len: the length of the buffer (given by find()).
+ * len: the length of the buffer
* Note that contents are conventionally little-endian.
* @get_status: read the status byte
* vdev: the virtio_device
@@ -50,62 +43,63 @@
* @set_status: write the status byte
* vdev: the virtio_device
* status: the new status byte
- * @find_vq: find the first VIRTIO_CONFIG_F_VIRTQUEUE and create a virtqueue.
+ * @find_vq: find a virtqueue and instantiate it.
* vdev: the virtio_device
+ * index: the 0-based virtqueue number in case there's more than one.
* callback: the virqtueue callback
- * Returns the new virtqueue or ERR_PTR().
+ * Returns the new virtqueue or ERR_PTR() (eg. -ENOENT).
* @del_vq: free a virtqueue found by find_vq().
*/
struct virtio_config_ops
{
- void *(*find)(struct virtio_device *vdev, u8 type, unsigned *len);
- void (*get)(struct virtio_device *vdev, void *token,
+ bool (*feature)(struct virtio_device *vdev, unsigned bit);
+ void (*get)(struct virtio_device *vdev, unsigned offset,
void *buf, unsigned len);
- void (*set)(struct virtio_device *vdev, void *token,
+ void (*set)(struct virtio_device *vdev, unsigned offset,
const void *buf, unsigned len);
u8 (*get_status)(struct virtio_device *vdev);
void (*set_status)(struct virtio_device *vdev, u8 status);
struct virtqueue *(*find_vq)(struct virtio_device *vdev,
+ unsigned index,
bool (*callback)(struct virtqueue *));
void (*del_vq)(struct virtqueue *vq);
};
/**
- * virtio_config_val - get a single virtio config and mark it used.
- * @config: the virtio config space
- * @type: the type to search for.
+ * virtio_config_val - look for a feature and get a single virtio config.
+ * @vdev: the virtio device
+ * @fbit: the feature bit
+ * @offset: the type to search for.
* @val: a pointer to the value to fill in.
*
- * Once used, the config type is marked with VIRTIO_CONFIG_F_USED so it can't
- * be found again. This version does endian conversion. */
-#define virtio_config_val(vdev, type, v) ({ \
- int _err = __virtio_config_val((vdev),(type),(v),sizeof(*(v))); \
- \
- BUILD_BUG_ON(sizeof(*(v)) != 1 && sizeof(*(v)) != 2 \
- && sizeof(*(v)) != 4 && sizeof(*(v)) != 8); \
- if (!_err) { \
- switch (sizeof(*(v))) { \
- case 2: le16_to_cpus((__u16 *) v); break; \
- case 4: le32_to_cpus((__u32 *) v); break; \
- case 8: le64_to_cpus((__u64 *) v); break; \
- } \
- } \
+ * The return value is -ENOENT if the feature doesn't exist. Otherwise
+ * the value is endian-corrected and returned in v. */
+#define virtio_config_val(vdev, fbit, offset, v) ({ \
+ int _err; \
+ if ((vdev)->config->feature((vdev), (fbit))) { \
+ __virtio_config_val((vdev), (offset), (v)); \
+ _err = 0; \
+ } else \
+ _err = -ENOENT; \
_err; \
})
-int __virtio_config_val(struct virtio_device *dev,
- u8 type, void *val, size_t size);
-
/**
- * virtio_use_bit - helper to use a feature bit in a bitfield value.
- * @dev: the virtio device
- * @token: the token as returned from vdev->config->find().
- * @len: the length of the field.
- * @bitnum: the bit to test.
+ * __virtio_config_val - get a single virtio config without feature check.
+ * @vdev: the virtio device
+ * @offset: the type to search for.
+ * @val: a pointer to the value to fill in.
*
- * If handed a NULL token, it returns false, otherwise returns bit status.
- * If it's one, it sets the mirroring acknowledgement bit. */
-int virtio_use_bit(struct virtio_device *vdev,
- void *token, unsigned int len, unsigned int bitnum);
+ * The value is endian-corrected and returned in v. */
+#define __virtio_config_val(vdev, offset, v) do { \
+ BUILD_BUG_ON(sizeof(*(v)) != 1 && sizeof(*(v)) != 2 \
+ && sizeof(*(v)) != 4 && sizeof(*(v)) != 8); \
+ (vdev)->config->get((vdev), (offset), (v), sizeof(*(v))); \
+ switch (sizeof(*(v))) { \
+ case 2: le16_to_cpus((__u16 *) v); break; \
+ case 4: le32_to_cpus((__u32 *) v); break; \
+ case 8: le64_to_cpus((__u64 *) v); break; \
+ } \
+} while(0)
#endif /* __KERNEL__ */
#endif /* _LINUX_VIRTIO_CONFIG_H */