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![Michael S. Tsirkin](/assets/img/avatar_default.png)
Add an API that tells the other side that callbacks should be delayed until a lot of work has been done. Implement using the new event_idx feature. Note: it might seem advantageous to let the drivers ask for a callback after a specific capacity has been reached. However, as a single head can free many entries in the descriptor table, we don't really have a clue about capacity until get_buf is called. The API is the simplest to implement at the moment, we'll see what kind of hints drivers can pass when there's more than one user of the feature. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
148 lines
5.4 KiB
C
148 lines
5.4 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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#include <linux/gfp.h>
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/**
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* virtqueue - a queue to register buffers for sending or receiving.
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* @list: the chain of virtqueues for this device
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* @callback: the function to call when buffers are consumed (can be NULL).
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* @name: the name of this virtqueue (mainly for debugging)
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* @vdev: the virtio device this queue was created for.
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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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struct list_head list;
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void (*callback)(struct virtqueue *vq);
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const char *name;
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struct virtio_device *vdev;
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void *priv;
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};
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/**
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* operations for virtqueue
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* virtqueue_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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* gfp: how to do memory allocations (if necessary).
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* Returns remaining capacity of queue (sg segments) or a negative error.
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* virtqueue_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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* virtqueue_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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* virtqueue_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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* virtqueue_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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* virtqueue_enable_cb_delayed: 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 but hints to the other side to delay
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* interrupts until most of the available buffers have been processed;
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* it returns "false" if there are many pending buffers in the queue,
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* to detect a possible race between the driver checking for more work,
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* and enabling callbacks.
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* virtqueue_detach_unused_buf: detach first unused buffer
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* vq: the struct virtqueue we're talking about.
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* Returns NULL or the "data" token handed to add_buf
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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 virtqueue_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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int virtqueue_add_buf_gfp(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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gfp_t gfp);
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static inline int virtqueue_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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{
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return virtqueue_add_buf_gfp(vq, sg, out_num, in_num, data, GFP_ATOMIC);
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}
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void virtqueue_kick(struct virtqueue *vq);
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void *virtqueue_get_buf(struct virtqueue *vq, unsigned int *len);
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void virtqueue_disable_cb(struct virtqueue *vq);
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bool virtqueue_enable_cb(struct virtqueue *vq);
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bool virtqueue_enable_cb_delayed(struct virtqueue *vq);
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void *virtqueue_detach_unused_buf(struct virtqueue *vq);
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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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* @vqs: the list of virtqueues 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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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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struct list_head vqs;
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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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#define dev_to_virtio(dev) container_of(dev, struct virtio_device, dev)
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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 0 or -errno.
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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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