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https://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson
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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>
121 lines
4.2 KiB
C
121 lines
4.2 KiB
C
#ifndef _LINUX_VIRTIO_H
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#define _LINUX_VIRTIO_H
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/* Everything a virtio driver needs to work with any particular virtio
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* implementation. */
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#include <linux/types.h>
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#include <linux/scatterlist.h>
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#include <linux/spinlock.h>
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#include <linux/device.h>
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#include <linux/mod_devicetable.h>
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/**
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* virtqueue - a queue to register buffers for sending or receiving.
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* @callback: the function to call when buffers are consumed (can be NULL).
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* @vdev: the virtio device this queue was created for.
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* @vq_ops: the operations for this virtqueue (see below).
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* @priv: a pointer for the virtqueue implementation to use.
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*/
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struct virtqueue
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{
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void (*callback)(struct virtqueue *vq);
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struct virtio_device *vdev;
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struct virtqueue_ops *vq_ops;
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void *priv;
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};
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/**
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* virtqueue_ops - operations for virtqueue abstraction layer
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* @add_buf: expose buffer to other end
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* vq: the struct virtqueue we're talking about.
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* sg: the description of the buffer(s).
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* out_num: the number of sg readable by other side
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* in_num: the number of sg which are writable (after readable ones)
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* data: the token identifying the buffer.
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* Returns 0 or an error.
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* @kick: update after add_buf
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* vq: the struct virtqueue
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* After one or more add_buf calls, invoke this to kick the other side.
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* @get_buf: get the next used buffer
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* vq: the struct virtqueue we're talking about.
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* len: the length written into the buffer
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* Returns NULL or the "data" token handed to add_buf.
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* @disable_cb: disable callbacks
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* vq: the struct virtqueue we're talking about.
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* Note that this is not necessarily synchronous, hence unreliable and only
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* useful as an optimization.
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* @enable_cb: restart callbacks after disable_cb.
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* vq: the struct virtqueue we're talking about.
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* This re-enables callbacks; it returns "false" if there are pending
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* buffers in the queue, to detect a possible race between the driver
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* checking for more work, and enabling callbacks.
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*
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* Locking rules are straightforward: the driver is responsible for
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* locking. No two operations may be invoked simultaneously, with the exception
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* of @disable_cb.
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*
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* All operations can be called in any context.
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*/
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struct virtqueue_ops {
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int (*add_buf)(struct virtqueue *vq,
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struct scatterlist sg[],
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unsigned int out_num,
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unsigned int in_num,
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void *data);
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void (*kick)(struct virtqueue *vq);
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void *(*get_buf)(struct virtqueue *vq, unsigned int *len);
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void (*disable_cb)(struct virtqueue *vq);
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bool (*enable_cb)(struct virtqueue *vq);
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};
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/**
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* virtio_device - representation of a device using virtio
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* @index: unique position on the virtio bus
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* @dev: underlying device.
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* @id: the device type identification (used to match it with a driver).
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* @config: the configuration ops for this device.
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* @features: the features supported by both driver and device.
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* @priv: private pointer for the driver's use.
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*/
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struct virtio_device
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{
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int index;
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struct device dev;
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struct virtio_device_id id;
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struct virtio_config_ops *config;
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/* Note that this is a Linux set_bit-style bitmap. */
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unsigned long features[1];
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void *priv;
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};
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int register_virtio_device(struct virtio_device *dev);
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void unregister_virtio_device(struct virtio_device *dev);
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/**
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* virtio_driver - operations for a virtio I/O driver
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* @driver: underlying device driver (populate name and owner).
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* @id_table: the ids serviced by this driver.
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* @feature_table: an array of feature numbers supported by this device.
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* @feature_table_size: number of entries in the feature table array.
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* @probe: the function to call when a device is found. Returns a token for
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* remove, or PTR_ERR().
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* @remove: the function when a device is removed.
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* @config_changed: optional function to call when the device configuration
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* changes; may be called in interrupt context.
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*/
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struct virtio_driver {
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struct device_driver driver;
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const struct virtio_device_id *id_table;
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const unsigned int *feature_table;
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unsigned int feature_table_size;
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int (*probe)(struct virtio_device *dev);
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void (*remove)(struct virtio_device *dev);
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void (*config_changed)(struct virtio_device *dev);
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};
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int register_virtio_driver(struct virtio_driver *drv);
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void unregister_virtio_driver(struct virtio_driver *drv);
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#endif /* _LINUX_VIRTIO_H */
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