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: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com> Reviewed-by: Juergen Gross <jgross@suse.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Oleksandr Andrushchenko
Takashi Iwai
parent
6d08b06e67
commit
cc3196ae19
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@ -96,6 +96,8 @@ source "sound/x86/Kconfig"
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source "sound/synth/Kconfig"
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source "sound/xen/Kconfig"
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endif # SND
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endif # !UML
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@ -5,7 +5,7 @@
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obj-$(CONFIG_SOUND) += soundcore.o
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obj-$(CONFIG_DMASOUND) += oss/dmasound/
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obj-$(CONFIG_SND) += core/ i2c/ drivers/ isa/ pci/ ppc/ arm/ sh/ synth/ usb/ \
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firewire/ sparc/ spi/ parisc/ pcmcia/ mips/ soc/ atmel/ hda/ x86/
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firewire/ sparc/ spi/ parisc/ pcmcia/ mips/ soc/ atmel/ hda/ x86/ xen/
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obj-$(CONFIG_SND_AOA) += aoa/
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# This one must be compilable even if sound is configured out
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@ -0,0 +1,10 @@
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# ALSA Xen drivers
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config SND_XEN_FRONTEND
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tristate "Xen para-virtualized sound frontend driver"
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depends on XEN
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select SND_PCM
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select XEN_XENBUS_FRONTEND
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help
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Choose this option if you want to enable a para-virtualized
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frontend sound driver for Xen guest OSes.
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@ -0,0 +1,5 @@
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# SPDX-License-Identifier: GPL-2.0 OR MIT
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snd_xen_front-objs := xen_snd_front.o
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obj-$(CONFIG_SND_XEN_FRONTEND) += snd_xen_front.o
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@ -0,0 +1,196 @@
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// SPDX-License-Identifier: GPL-2.0 OR MIT
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/*
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* Xen para-virtual sound device
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*
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* Copyright (C) 2016-2018 EPAM Systems Inc.
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*
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* Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
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*/
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#include <linux/delay.h>
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#include <linux/module.h>
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#include <xen/platform_pci.h>
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#include <xen/xen.h>
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#include <xen/xenbus.h>
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#include <xen/interface/io/sndif.h>
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#include "xen_snd_front.h"
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static void xen_snd_drv_fini(struct xen_snd_front_info *front_info)
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{
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}
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static int sndback_initwait(struct xen_snd_front_info *front_info)
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{
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return 0;
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}
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static int sndback_connect(struct xen_snd_front_info *front_info)
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{
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return 0;
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}
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static void sndback_disconnect(struct xen_snd_front_info *front_info)
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{
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xen_snd_drv_fini(front_info);
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xenbus_switch_state(front_info->xb_dev, XenbusStateInitialising);
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}
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static void sndback_changed(struct xenbus_device *xb_dev,
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enum xenbus_state backend_state)
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{
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struct xen_snd_front_info *front_info = dev_get_drvdata(&xb_dev->dev);
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int ret;
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dev_dbg(&xb_dev->dev, "Backend state is %s, front is %s\n",
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xenbus_strstate(backend_state),
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xenbus_strstate(xb_dev->state));
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switch (backend_state) {
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case XenbusStateReconfiguring:
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/* fall through */
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case XenbusStateReconfigured:
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/* fall through */
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case XenbusStateInitialised:
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/* fall through */
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break;
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case XenbusStateInitialising:
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/* Recovering after backend unexpected closure. */
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sndback_disconnect(front_info);
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break;
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case XenbusStateInitWait:
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/* Recovering after backend unexpected closure. */
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sndback_disconnect(front_info);
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ret = sndback_initwait(front_info);
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if (ret < 0)
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xenbus_dev_fatal(xb_dev, ret, "initializing frontend");
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else
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xenbus_switch_state(xb_dev, XenbusStateInitialised);
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break;
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case XenbusStateConnected:
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if (xb_dev->state != XenbusStateInitialised)
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break;
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ret = sndback_connect(front_info);
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if (ret < 0)
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xenbus_dev_fatal(xb_dev, ret, "initializing frontend");
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else
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xenbus_switch_state(xb_dev, XenbusStateConnected);
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break;
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case XenbusStateClosing:
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/*
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* In this state backend starts freeing resources,
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* so let it go into closed state first, so we can also
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* remove ours.
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*/
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break;
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case XenbusStateUnknown:
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/* fall through */
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case XenbusStateClosed:
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if (xb_dev->state == XenbusStateClosed)
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break;
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sndback_disconnect(front_info);
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break;
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}
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}
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static int xen_drv_probe(struct xenbus_device *xb_dev,
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const struct xenbus_device_id *id)
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{
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struct xen_snd_front_info *front_info;
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front_info = devm_kzalloc(&xb_dev->dev,
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sizeof(*front_info), GFP_KERNEL);
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if (!front_info)
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return -ENOMEM;
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front_info->xb_dev = xb_dev;
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dev_set_drvdata(&xb_dev->dev, front_info);
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return xenbus_switch_state(xb_dev, XenbusStateInitialising);
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}
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static int xen_drv_remove(struct xenbus_device *dev)
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{
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struct xen_snd_front_info *front_info = dev_get_drvdata(&dev->dev);
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int to = 100;
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xenbus_switch_state(dev, XenbusStateClosing);
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/*
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* On driver removal it is disconnected from XenBus,
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* so no backend state change events come via .otherend_changed
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* callback. This prevents us from exiting gracefully, e.g.
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* signaling the backend to free event channels, waiting for its
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* state to change to XenbusStateClosed and cleaning at our end.
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* Normally when front driver removed backend will finally go into
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* XenbusStateInitWait state.
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*
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* Workaround: read backend's state manually and wait with time-out.
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*/
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while ((xenbus_read_unsigned(front_info->xb_dev->otherend, "state",
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XenbusStateUnknown) != XenbusStateInitWait) &&
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to--)
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msleep(10);
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if (!to) {
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unsigned int state;
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state = xenbus_read_unsigned(front_info->xb_dev->otherend,
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"state", XenbusStateUnknown);
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pr_err("Backend state is %s while removing driver\n",
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xenbus_strstate(state));
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}
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xen_snd_drv_fini(front_info);
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xenbus_frontend_closed(dev);
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return 0;
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}
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static const struct xenbus_device_id xen_drv_ids[] = {
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{ XENSND_DRIVER_NAME },
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{ "" }
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};
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static struct xenbus_driver xen_driver = {
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.ids = xen_drv_ids,
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.probe = xen_drv_probe,
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.remove = xen_drv_remove,
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.otherend_changed = sndback_changed,
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};
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static int __init xen_drv_init(void)
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{
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if (!xen_domain())
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return -ENODEV;
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if (!xen_has_pv_devices())
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return -ENODEV;
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pr_info("Initialising Xen " XENSND_DRIVER_NAME " frontend driver\n");
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return xenbus_register_frontend(&xen_driver);
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}
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static void __exit xen_drv_fini(void)
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{
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pr_info("Unregistering Xen " XENSND_DRIVER_NAME " frontend driver\n");
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xenbus_unregister_driver(&xen_driver);
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}
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module_init(xen_drv_init);
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module_exit(xen_drv_fini);
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MODULE_DESCRIPTION("Xen virtual sound device frontend");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS("xen:" XENSND_DRIVER_NAME);
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MODULE_SUPPORTED_DEVICE("{{ALSA,Virtual soundcard}}");
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@ -0,0 +1,18 @@
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/* SPDX-License-Identifier: GPL-2.0 OR MIT */
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/*
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* Xen para-virtual sound device
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*
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* Copyright (C) 2016-2018 EPAM Systems Inc.
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*
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* Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
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*/
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#ifndef __XEN_SND_FRONT_H
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#define __XEN_SND_FRONT_H
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struct xen_snd_front_info {
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struct xenbus_device *xb_dev;
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};
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#endif /* __XEN_SND_FRONT_H */
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