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This commit uses the ack() callback to determine when a buffer has been updated, then exposes it to guest. The current mechanism splits a dma buffer into descriptors that are exposed to the device. This dma buffer is shared with the user application. When the device consumes a buffer, the driver moves the request from the used ring to available ring. The driver exposes the buffer to the device without knowing if the content has been updated from the user. The section 2.8.21.1 of the virtio spec states that: "The device MAY access the descriptor chains the driver created and the memory they refer to immediately". If the device picks up buffers from the available ring just after it is notified, it happens that the content may be old. When the ack() callback is invoked, the driver exposes only the buffers that have already been updated, i.e., enqueued in the available ring. Thus, the device always picks up a buffer that is updated. For capturing, the driver starts by exposing all the available buffers to device. After device updates the content of a buffer, it enqueues it in the used ring. It is only after the ack() for capturing is issued that the driver re-enqueues the buffer in the available ring. Co-developed-by: Anton Yakovlev <anton.yakovlev@opensynergy.com> Signed-off-by: Anton Yakovlev <anton.yakovlev@opensynergy.com> Signed-off-by: Matias Ezequiel Vara Larsen <mvaralar@redhat.com> Link: https://lore.kernel.org/r/ZTjkn1YAFz67yfqx@fedora Signed-off-by: Takashi Iwai <tiwai@suse.de> |
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| .. | ||
| Kconfig | ||
| Makefile | ||
| virtio_card.c | ||
| virtio_card.h | ||
| virtio_chmap.c | ||
| virtio_ctl_msg.c | ||
| virtio_ctl_msg.h | ||
| virtio_jack.c | ||
| virtio_pcm_msg.c | ||
| virtio_pcm_ops.c | ||
| virtio_pcm.c | ||
| virtio_pcm.h | ||