Date:	Tue, 16 Jun 2015 07:45:14 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Juergen Gross <jgross@...e.com>
Cc:	linux-kernel@...r.kernel.org, xen-devel@...ts.xensource.com,
	konrad.wilk@...cle.com, david.vrabel@...rix.com,
	boris.ostrovsky@...cle.com, linux-usb@...r.kernel.org
Subject: Re: [Patch V3 2/3] usb: Introduce Xen pvUSB frontend (xen hcd)

On Tue, Jun 16, 2015 at 04:32:34PM +0200, Juergen Gross wrote:
> Introduces the Xen pvUSB frontend. With pvUSB it is possible for a Xen
> domU to communicate with a USB device assigned to that domU. The
> communication is all done via the pvUSB backend in a driver domain
> (usually Dom0) which is owner of the physical device.
> 
> The pvUSB frontend is a USB hcd for a virtual USB host connector.
> 
> The code is taken from the pvUSB implementation in Xen done by Fujitsu
> based on Linux kernel 2.6.18.
> 
> Changes from the original version are:
> - port to upstream kernel
> - put all code in just one source file
> - move module to appropriate location in kernel tree
> - adapt to Linux style guide
> - minor code modifications to increase readability
> 
> Signed-off-by: Juergen Gross <jgross@...e.com>
> ---
>  drivers/usb/host/Kconfig   |   11 +
>  drivers/usb/host/Makefile  |    1 +
>  drivers/usb/host/xen-hcd.c | 1638 ++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 1650 insertions(+)
>  create mode 100644 drivers/usb/host/xen-hcd.c
> 
> diff --git a/drivers/usb/host/Kconfig b/drivers/usb/host/Kconfig
> index 197a6a3..3361b4b 100644
> --- a/drivers/usb/host/Kconfig
> +++ b/drivers/usb/host/Kconfig
> @@ -788,3 +788,14 @@ config USB_HCD_TEST_MODE
>  	  This option is of interest only to developers who need to validate
>  	  their USB hardware designs.  It is not needed for normal use.  If
>  	  unsure, say N.
> +
> +config USB_XEN_HCD
> +	tristate "Xen usb virtual host driver"
> +	depends on XEN
> +	select XEN_XENBUS_FRONTEND
> +	help
> +	  The Xen usb virtual host driver serves as a frontend driver enabling
> +	  a Xen guest system to access USB Devices passed through to the guest
> +	  by the Xen host (usually Dom0).
> +	  Only needed if the kernel is running in a Xen guest and generic
> +	  access to a USB device is needed.
> diff --git a/drivers/usb/host/Makefile b/drivers/usb/host/Makefile
> index 65b0b6a..3779696 100644
> --- a/drivers/usb/host/Makefile
> +++ b/drivers/usb/host/Makefile
> @@ -75,3 +75,4 @@ obj-$(CONFIG_USB_HCD_SSB)	+= ssb-hcd.o
>  obj-$(CONFIG_USB_FUSBH200_HCD)	+= fusbh200-hcd.o
>  obj-$(CONFIG_USB_FOTG210_HCD)	+= fotg210-hcd.o
>  obj-$(CONFIG_USB_MAX3421_HCD)	+= max3421-hcd.o
> +obj-$(CONFIG_USB_XEN_HCD)	+= xen-hcd.o
> diff --git a/drivers/usb/host/xen-hcd.c b/drivers/usb/host/xen-hcd.c
> new file mode 100644
> index 0000000..9da2856
> --- /dev/null
> +++ b/drivers/usb/host/xen-hcd.c
> @@ -0,0 +1,1638 @@
> +/*
> + * xen-hcd.c
> + *
> + * Xen USB Virtual Host Controller driver
> + *
> + * Copyright (C) 2009, FUJITSU LABORATORIES LTD.
> + * Author: Noboru Iwamatsu <n_iwamatsu@...fujitsu.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, see <http://www.gnu.org/licenses/>.
> + *
> + * Or, by your choice:
> + *
> + * When distributed separately from the Linux kernel or incorporated into
> + * other software packages, subject to the following license:
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a copy
> + * of this software and associated documentation files (the "Software"), to
> + * deal in the Software without restriction, including without limitation the
> + * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
> + * sell copies of the Software, and to permit persons to whom the Software is
> + * furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
> + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
> + * DEALINGS IN THE SOFTWARE.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/usb.h>
> +#include <linux/list.h>
> +#include <linux/usb/hcd.h>
> +#include <linux/io.h>
> +
> +#include <xen/xen.h>
> +#include <xen/xenbus.h>
> +#include <xen/grant_table.h>
> +#include <xen/events.h>
> +#include <xen/page.h>
> +
> +#include <xen/interface/io/usbif.h>
> +
> +/* Private per-URB data */
> +struct urb_priv {
> +	struct list_head list;
> +	struct urb *urb;
> +	int req_id;		/* RING_REQUEST id for submitting */
> +	int unlink_req_id;	/* RING_REQUEST id for unlinking */
> +	int status;
> +	unsigned unlinked:1;	/* dequeued marker */
> +};
> +
> +/* virtual roothub port status */
> +struct rhport_status {
> +	__u32 status;
> +	unsigned resuming:1;		/* in resuming */
> +	unsigned c_connection:1;	/* connection changed */
> +	unsigned long timeout;
> +};
> +
> +/* status of attached device */
> +struct vdevice_status {
> +	int devnum;
> +	enum usb_device_state status;
> +	enum usb_device_speed speed;
> +};
> +
> +/* RING request shadow */
> +struct usb_shadow {
> +	struct xenusb_urb_request req;
> +	struct urb *urb;
> +};
> +
> +struct xenhcd_info {
> +	/* Virtual Host Controller has 4 urb queues */
> +	struct list_head pending_submit_list;
> +	struct list_head pending_unlink_list;
> +	struct list_head in_progress_list;
> +	struct list_head giveback_waiting_list;
> +
> +	spinlock_t lock;
> +
> +	/* timer that kick pending and giveback waiting urbs */
> +	struct timer_list watchdog;
> +	unsigned long actions;
> +
> +	/* virtual root hub */
> +	int rh_numports;
> +	struct rhport_status ports[XENUSB_MAX_PORTNR];
> +	struct vdevice_status devices[XENUSB_MAX_PORTNR];
> +
> +	/* Xen related staff */
> +	struct xenbus_device *xbdev;
> +	int urb_ring_ref;
> +	int conn_ring_ref;
> +	struct xenusb_urb_front_ring urb_ring;
> +	struct xenusb_conn_front_ring conn_ring;
> +
> +	unsigned int evtchn;
> +	unsigned int irq;
> +	struct usb_shadow shadow[XENUSB_URB_RING_SIZE];
> +	unsigned shadow_free;
> +};
> +
> +#define GRANT_INVALID_REF 0
> +
> +#define XENHCD_RING_JIFFIES (HZ/200)
> +#define XENHCD_SCAN_JIFFIES 1
> +
> +enum xenhcd_timer_action {
> +	TIMER_RING_WATCHDOG,
> +	TIMER_SCAN_PENDING_URBS,
> +};
> +
> +static struct kmem_cache *xenhcd_urbp_cachep;
> +
> +static inline struct xenhcd_info *xenhcd_hcd_to_info(struct usb_hcd *hcd)
> +{
> +	return (struct xenhcd_info *)hcd->hcd_priv;
> +}
> +
> +static inline struct usb_hcd *xenhcd_info_to_hcd(struct xenhcd_info *info)
> +{
> +	return container_of((void *)info, struct usb_hcd, hcd_priv);
> +}
> +
> +static inline void xenhcd_timer_action_done(struct xenhcd_info *info,
> +					    enum xenhcd_timer_action action)
> +{
> +	clear_bit(action, &info->actions);
> +}
> +
> +static void xenhcd_timer_action(struct xenhcd_info *info,
> +				enum xenhcd_timer_action action)
> +{
> +	if (timer_pending(&info->watchdog) &&
> +	    test_bit(TIMER_SCAN_PENDING_URBS, &info->actions))
> +		return;
> +
> +	if (!test_and_set_bit(action, &info->actions)) {
> +		unsigned long t;
> +
> +		switch (action) {
> +		case TIMER_RING_WATCHDOG:
> +			t = XENHCD_RING_JIFFIES;
> +			break;
> +		default:
> +			t = XENHCD_SCAN_JIFFIES;
> +			break;
> +		}
> +		mod_timer(&info->watchdog, t + jiffies);
> +	}
> +}
> +
> +static ssize_t xenhcd_show_statistics(struct device *dev,
> +				      struct device_attribute *attr, char *buf)
> +{
> +	struct usb_hcd *hcd;
> +	struct xenhcd_info *info;
> +	unsigned long flags;
> +	unsigned size;
> +
> +	hcd = dev_get_drvdata(dev);
> +	info = xenhcd_hcd_to_info(hcd);
> +
> +	spin_lock_irqsave(&info->lock, flags);
> +
> +	size = scnprintf(buf, PAGE_SIZE, "bus %s, device %s\n%s\n"
> +			 "xenhcd, hcd state %d\n",
> +			 hcd->self.controller->bus->name,
> +			 dev_name(hcd->self.controller), hcd->product_desc,
> +			 hcd->state);
> +
> +	spin_unlock_irqrestore(&info->lock, flags);
> +
> +	return size;
> +}
> +
> +static DEVICE_ATTR(statistics, S_IRUGO, xenhcd_show_statistics, NULL);

DEVICE_ATTR_RO() please.

As you are adding new sysfs files, we need Documentation/ABI/ entries.

Also note that I will reject this sysfs file for the obvious reasons
that it violates the one-value-per-file sysfs rule.  Nice try to sneak
this one by, don't ever do that again.

greg k-h
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