diff options
Diffstat (limited to 'sound/xen/xen_snd_front.c')
| -rw-r--r-- | sound/xen/xen_snd_front.c | 196 |
1 files changed, 196 insertions, 0 deletions
diff --git a/sound/xen/xen_snd_front.c b/sound/xen/xen_snd_front.c new file mode 100644 index 000000000000..bbbe2767b565 --- /dev/null +++ b/sound/xen/xen_snd_front.c @@ -0,0 +1,196 @@ +// 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}}"); |