Commit cc3196ae authored by Oleksandr Andrushchenko's avatar Oleksandr Andrushchenko Committed by Takashi Iwai

ALSA: xen-front: Introduce Xen para-virtualized sound frontend driver

Introduce skeleton of the para-virtualized Xen sound
frontend driver.

Initial handling for Xen bus states: implement
Xen bus state machine for the frontend driver according to
the state diagram and recovery flow from sound para-virtualized
protocol: xen/interface/io/sndif.h.
Signed-off-by: 's avatarOleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Reviewed-by: 's avatarJuergen Gross <jgross@suse.com>
Signed-off-by: 's avatarTakashi Iwai <tiwai@suse.de>
parent 6d08b06e
......@@ -96,6 +96,8 @@ source "sound/x86/Kconfig"
source "sound/synth/Kconfig"
source "sound/xen/Kconfig"
endif # SND
endif # !UML
......
......@@ -5,7 +5,7 @@
obj-$(CONFIG_SOUND) += soundcore.o
obj-$(CONFIG_DMASOUND) += oss/dmasound/
obj-$(CONFIG_SND) += core/ i2c/ drivers/ isa/ pci/ ppc/ arm/ sh/ synth/ usb/ \
firewire/ sparc/ spi/ parisc/ pcmcia/ mips/ soc/ atmel/ hda/ x86/
firewire/ sparc/ spi/ parisc/ pcmcia/ mips/ soc/ atmel/ hda/ x86/ xen/
obj-$(CONFIG_SND_AOA) += aoa/
# This one must be compilable even if sound is configured out
......
# ALSA Xen drivers
config SND_XEN_FRONTEND
tristate "Xen para-virtualized sound frontend driver"
depends on XEN
select SND_PCM
select XEN_XENBUS_FRONTEND
help
Choose this option if you want to enable a para-virtualized
frontend sound driver for Xen guest OSes.
# SPDX-License-Identifier: GPL-2.0 OR MIT
snd_xen_front-objs := xen_snd_front.o
obj-$(CONFIG_SND_XEN_FRONTEND) += snd_xen_front.o
// SPDX-License-Identifier: GPL-2.0 OR MIT
/*
* Xen para-virtual sound device
*
* Copyright (C) 2016-2018 EPAM Systems Inc.
*
* Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
*/
#include <linux/delay.h>
#include <linux/module.h>
#include <xen/platform_pci.h>
#include <xen/xen.h>
#include <xen/xenbus.h>
#include <xen/interface/io/sndif.h>
#include "xen_snd_front.h"
static void xen_snd_drv_fini(struct xen_snd_front_info *front_info)
{
}
static int sndback_initwait(struct xen_snd_front_info *front_info)
{
return 0;
}
static int sndback_connect(struct xen_snd_front_info *front_info)
{
return 0;
}
static void sndback_disconnect(struct xen_snd_front_info *front_info)
{
xen_snd_drv_fini(front_info);
xenbus_switch_state(front_info->xb_dev, XenbusStateInitialising);
}
static void sndback_changed(struct xenbus_device *xb_dev,
enum xenbus_state backend_state)
{
struct xen_snd_front_info *front_info = dev_get_drvdata(&xb_dev->dev);
int ret;
dev_dbg(&xb_dev->dev, "Backend state is %s, front is %s\n",
xenbus_strstate(backend_state),
xenbus_strstate(xb_dev->state));
switch (backend_state) {
case XenbusStateReconfiguring:
/* fall through */
case XenbusStateReconfigured:
/* fall through */
case XenbusStateInitialised:
/* fall through */
break;
case XenbusStateInitialising:
/* Recovering after backend unexpected closure. */
sndback_disconnect(front_info);
break;
case XenbusStateInitWait:
/* Recovering after backend unexpected closure. */
sndback_disconnect(front_info);
ret = sndback_initwait(front_info);
if (ret < 0)
xenbus_dev_fatal(xb_dev, ret, "initializing frontend");
else
xenbus_switch_state(xb_dev, XenbusStateInitialised);
break;
case XenbusStateConnected:
if (xb_dev->state != XenbusStateInitialised)
break;
ret = sndback_connect(front_info);
if (ret < 0)
xenbus_dev_fatal(xb_dev, ret, "initializing frontend");
else
xenbus_switch_state(xb_dev, XenbusStateConnected);
break;
case XenbusStateClosing:
/*
* In this state backend starts freeing resources,
* so let it go into closed state first, so we can also
* remove ours.
*/
break;
case XenbusStateUnknown:
/* fall through */
case XenbusStateClosed:
if (xb_dev->state == XenbusStateClosed)
break;
sndback_disconnect(front_info);
break;
}
}
static int xen_drv_probe(struct xenbus_device *xb_dev,
const struct xenbus_device_id *id)
{
struct xen_snd_front_info *front_info;
front_info = devm_kzalloc(&xb_dev->dev,
sizeof(*front_info), GFP_KERNEL);
if (!front_info)
return -ENOMEM;
front_info->xb_dev = xb_dev;
dev_set_drvdata(&xb_dev->dev, front_info);
return xenbus_switch_state(xb_dev, XenbusStateInitialising);
}
static int xen_drv_remove(struct xenbus_device *dev)
{
struct xen_snd_front_info *front_info = dev_get_drvdata(&dev->dev);
int to = 100;
xenbus_switch_state(dev, XenbusStateClosing);
/*
* On driver removal it is disconnected from XenBus,
* so no backend state change events come via .otherend_changed
* callback. This prevents us from exiting gracefully, e.g.
* signaling the backend to free event channels, waiting for its
* state to change to XenbusStateClosed and cleaning at our end.
* Normally when front driver removed backend will finally go into
* XenbusStateInitWait state.
*
* Workaround: read backend's state manually and wait with time-out.
*/
while ((xenbus_read_unsigned(front_info->xb_dev->otherend, "state",
XenbusStateUnknown) != XenbusStateInitWait) &&
to--)
msleep(10);
if (!to) {
unsigned int state;
state = xenbus_read_unsigned(front_info->xb_dev->otherend,
"state", XenbusStateUnknown);
pr_err("Backend state is %s while removing driver\n",
xenbus_strstate(state));
}
xen_snd_drv_fini(front_info);
xenbus_frontend_closed(dev);
return 0;
}
static const struct xenbus_device_id xen_drv_ids[] = {
{ XENSND_DRIVER_NAME },
{ "" }
};
static struct xenbus_driver xen_driver = {
.ids = xen_drv_ids,
.probe = xen_drv_probe,
.remove = xen_drv_remove,
.otherend_changed = sndback_changed,
};
static int __init xen_drv_init(void)
{
if (!xen_domain())
return -ENODEV;
if (!xen_has_pv_devices())
return -ENODEV;
pr_info("Initialising Xen " XENSND_DRIVER_NAME " frontend driver\n");
return xenbus_register_frontend(&xen_driver);
}
static void __exit xen_drv_fini(void)
{
pr_info("Unregistering Xen " XENSND_DRIVER_NAME " frontend driver\n");
xenbus_unregister_driver(&xen_driver);
}
module_init(xen_drv_init);
module_exit(xen_drv_fini);
MODULE_DESCRIPTION("Xen virtual sound device frontend");
MODULE_LICENSE("GPL");
MODULE_ALIAS("xen:" XENSND_DRIVER_NAME);
MODULE_SUPPORTED_DEVICE("{{ALSA,Virtual soundcard}}");
/* SPDX-License-Identifier: GPL-2.0 OR MIT */
/*
* Xen para-virtual sound device
*
* Copyright (C) 2016-2018 EPAM Systems Inc.
*
* Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
*/
#ifndef __XEN_SND_FRONT_H
#define __XEN_SND_FRONT_H
struct xen_snd_front_info {
struct xenbus_device *xb_dev;
};
#endif /* __XEN_SND_FRONT_H */
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