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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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c45a6816c1
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>
117 lines
4.1 KiB
C
117 lines
4.1 KiB
C
#ifndef _LINUX_VIRTIO_CONFIG_H
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#define _LINUX_VIRTIO_CONFIG_H
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/* Virtio devices use a standardized configuration space to define their
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* features and pass configuration information, but each implementation can
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* store and access that space differently. */
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#include <linux/types.h>
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/* Status byte for guest to report progress, and synchronize features. */
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/* We have seen device and processed generic fields (VIRTIO_CONFIG_F_VIRTIO) */
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#define VIRTIO_CONFIG_S_ACKNOWLEDGE 1
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/* We have found a driver for the device. */
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#define VIRTIO_CONFIG_S_DRIVER 2
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/* Driver has used its parts of the config, and is happy */
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#define VIRTIO_CONFIG_S_DRIVER_OK 4
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/* We've given up on this device. */
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#define VIRTIO_CONFIG_S_FAILED 0x80
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#ifdef __KERNEL__
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#include <linux/virtio.h>
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/**
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* virtio_config_ops - operations for configuring a virtio device
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* @get: read the value of a configuration field
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* vdev: the virtio_device
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* offset: the offset of the configuration field
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* buf: the buffer to write the field value into.
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* len: the length of the buffer
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* @set: write the value of a configuration field
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* vdev: the virtio_device
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* offset: the offset of the configuration field
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* buf: the buffer to read the field value from.
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* len: the length of the buffer
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* @get_status: read the status byte
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* vdev: the virtio_device
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* Returns the status byte
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* @set_status: write the status byte
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* vdev: the virtio_device
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* status: the new status byte
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* @reset: reset the device
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* vdev: the virtio device
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* After this, status and feature negotiation must be done again
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* @find_vq: find a virtqueue and instantiate it.
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* vdev: the virtio_device
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* index: the 0-based virtqueue number in case there's more than one.
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* callback: the virqtueue callback
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* Returns the new virtqueue or ERR_PTR() (eg. -ENOENT).
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* @del_vq: free a virtqueue found by find_vq().
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* @get_features: get the array of feature bits for this device.
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* vdev: the virtio_device
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* Returns the first 32 feature bits (all we currently need).
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* @set_features: confirm what device features we'll be using.
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* vdev: the virtio_device
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* feature: the first 32 feature bits
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*/
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struct virtio_config_ops
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{
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void (*get)(struct virtio_device *vdev, unsigned offset,
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void *buf, unsigned len);
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void (*set)(struct virtio_device *vdev, unsigned offset,
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const void *buf, unsigned len);
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u8 (*get_status)(struct virtio_device *vdev);
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void (*set_status)(struct virtio_device *vdev, u8 status);
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void (*reset)(struct virtio_device *vdev);
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struct virtqueue *(*find_vq)(struct virtio_device *vdev,
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unsigned index,
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void (*callback)(struct virtqueue *));
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void (*del_vq)(struct virtqueue *vq);
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u32 (*get_features)(struct virtio_device *vdev);
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void (*set_features)(struct virtio_device *vdev, u32 features);
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};
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/* If driver didn't advertise the feature, it will never appear. */
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void virtio_check_driver_offered_feature(const struct virtio_device *vdev,
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unsigned int fbit);
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/**
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* virtio_has_feature - helper to determine if this device has this feature.
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* @vdev: the device
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* @fbit: the feature bit
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*/
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static inline bool virtio_has_feature(const struct virtio_device *vdev,
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unsigned int fbit)
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{
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/* Did you forget to fix assumptions on max features? */
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if (__builtin_constant_p(fbit))
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BUILD_BUG_ON(fbit >= 32);
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virtio_check_driver_offered_feature(vdev, fbit);
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return test_bit(fbit, vdev->features);
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}
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/**
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* virtio_config_val - look for a feature and get a virtio config entry.
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* @vdev: the virtio device
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* @fbit: the feature bit
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* @offset: the type to search for.
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* @val: a pointer to the value to fill in.
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*
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* The return value is -ENOENT if the feature doesn't exist. Otherwise
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* the config value is copied into whatever is pointed to by v. */
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#define virtio_config_val(vdev, fbit, offset, v) \
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virtio_config_buf((vdev), (fbit), (offset), (v), sizeof(v))
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static inline int virtio_config_buf(struct virtio_device *vdev,
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unsigned int fbit,
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unsigned int offset,
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void *buf, unsigned len)
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{
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if (!virtio_has_feature(vdev, fbit))
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return -ENOENT;
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vdev->config->get(vdev, offset, buf, len);
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return 0;
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}
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#endif /* __KERNEL__ */
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#endif /* _LINUX_VIRTIO_CONFIG_H */
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