text: #ifndef _LINUX_VIRTIO_CONFIG_H
  #define _LINUX_VIRTIO_CONFIG_H
  /* This header, excluding the #ifdef __KERNEL__ part, is BSD licensed so
   * anyone can use the definitions to implement compatible drivers/servers.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. Neither the name of IBM nor the names of its contributors
   *    may be used to endorse or promote products derived from this software
   *    without specific prior written permission.
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED.  IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE. */
  
  /* Virtio devices use a standardized configuration space to define their
   * features and pass configuration information, but each implementation can
   * store and access that space differently. */
  #include "standard-headers/linux/types.h"
  
  /* 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. */
  #define VIRTIO_CONFIG_S_DRIVER		2
  /* Driver has used its parts of the config, and is happy */
  #define VIRTIO_CONFIG_S_DRIVER_OK	4
  /* Driver has finished configuring features */
  #define VIRTIO_CONFIG_S_FEATURES_OK	8
  /* Device entered invalid state, driver must reset it */
  #define VIRTIO_CONFIG_S_NEEDS_RESET	0x40
  /* We've given up on this device. */
  #define VIRTIO_CONFIG_S_FAILED		0x80
  
  /* Some virtio feature bits (currently bits 28 through 32) are reserved for the
   * transport being used (eg. virtio_ring), the rest are per-device feature
   * bits. */
  #define VIRTIO_TRANSPORT_F_START	28
  #define VIRTIO_TRANSPORT_F_END		34
  
  #ifndef VIRTIO_CONFIG_NO_LEGACY
  /* Do we get callbacks when the ring is completely used, even if we've
   * suppressed them? */
  #define VIRTIO_F_NOTIFY_ON_EMPTY	24
  
  /* Can the device handle any descriptor layout? */
  #define VIRTIO_F_ANY_LAYOUT		27
  #endif /* VIRTIO_CONFIG_NO_LEGACY */
  
  /* v1.0 compliant. */
  #define VIRTIO_F_VERSION_1		32
  
  /*
   * If clear - device has the IOMMU bypass quirk feature.
   * If set - use platform tools to detect the IOMMU.
   *
   * Note the reverse polarity (compared to most other features),
   * this is for compatibility with legacy systems.
   */
  #define VIRTIO_F_IOMMU_PLATFORM		33
  #endif /* _LINUX_VIRTIO_CONFIG_H */
  