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* ALSA: xen-front: remove redundant error check on retColin Ian King2018-05-281-2/+0
| | | | | | | | | | | | | The error for a -ve value in ret is redundant as all previous assignments to ret have an associated -ve check and hence it is impossible for ret to be less that zero at the point of the check. Remove this redundant error check. Detected by CoveritScan, CID#1469407 ("Logically Dead code") Signed-off-by: Colin Ian King <colin.king@canonical.com> Reviewed-by: Takashi Sakamoto <o-takashi@sakamocchi.jp> Signed-off-by: Takashi Iwai <tiwai@suse.de>
* ALSA: xen-front: Implement ALSA virtual sound driverOleksandr Andrushchenko2018-05-161-1/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Implement essential initialization of the sound driver: - introduce required data structures - handle driver registration - handle sound card registration - register sound driver on backend connection - remove sound driver on backend disconnect Initialize virtual sound card with streams according to the Xen store configuration. Implement ALSA driver operations including: - manage frontend/backend shared buffers - manage Xen bus event channel states Implement requests from front to back for ALSA PCM operations. - report ALSA period elapsed event: handle XENSND_EVT_CUR_POS notifications from the backend when stream position advances during playback/capture. The event carries a value of how many octets were played/captured at the time of the event. - implement explicit stream parameter negotiation between backend and frontend: handle XENSND_OP_HW_PARAM_QUERY request to read/update configuration space for the parameter given: request passes desired parameter interval and the response to this request returns min/max interval for the parameter to be used. Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
* ALSA: xen-front: Implement Xen event channel handlingOleksandr Andrushchenko2018-05-161-0/+494
Handle Xen event channels: - create for all configured streams and publish corresponding ring references and event channels in Xen store, so backend can connect - implement event channels interrupt handlers - create and destroy event channels with respect to Xen bus state Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>