Re: [Xen-devel] [Patch V1 3/3] xen: add pvUSB backend

[Juergen Gross]

Sorry, I just found time now to continue with this series.

On 27/10/15 19:54, Konrad Rzeszutek Wilk wrote:
> On Thu, Sep 03, 2015 at 12:45:13PM +0200, Juergen Gross wrote:
>> Add a backend for para-virtualized USB devices for xen domains.
>>
>> The backend is using host-libusb to forward USB requests from a
>> domain via libusb to the real device(s) passed through.
>>
>> Signed-off-by: Juergen Gross 
>> ---
>>  hw/usb/Makefile.objs |4 +
>>  hw/usb/xen-usb.c | 1120 
>> ++
>>  hw/xenpv/xen_machine_pv.c|3 +
>>  include/hw/xen/xen_backend.h |   13 +-
>>  4 files changed, 1137 insertions(+), 3 deletions(-)
>>  create mode 100644 hw/usb/xen-usb.c
>>
>> diff --git a/hw/usb/Makefile.objs b/hw/usb/Makefile.objs
>> index 3fe4dff..0253184 100644
>> --- a/hw/usb/Makefile.objs
>> +++ b/hw/usb/Makefile.objs
>> @@ -36,3 +36,7 @@ common-obj-$(CONFIG_USB_REDIR) += redirect.o quirks.o
>>  
>>  # usb pass-through
>>  common-obj-y += $(patsubst %,host-%.o,$(HOST_USB))
>> +
>> +ifeq ($(CONFIG_USB_LIBUSB),y)
>> +common-obj-$(CONFIG_XEN_BACKEND) += xen-usb.o
>> +endif
>> diff --git a/hw/usb/xen-usb.c b/hw/usb/xen-usb.c
>> new file mode 100644
>> index 000..2570bd7
>> --- /dev/null
>> +++ b/hw/usb/xen-usb.c
>> @@ -0,0 +1,1120 @@
>> +/*
>> + *  xen paravirt usb device backend
>> + *
>> + *  (c) Juergen Gross 
>> + *
>> + *  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; under version 2 of the License.
>> + *
>> + *  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 .
>> + *
>> + *  Contributions after 2012-01-13 are licensed under the terms of the
>> + *  GNU GPL, version 2 or (at your option) any later version.
>> + */
>> +
>> +#include 
>> +#include 
>> +#include 
>> +#include 
>> +
>> +#include "qemu-common.h"
>> +#include "qemu/config-file.h"
>> +#include "hw/sysbus.h"
>> +#include "hw/usb.h"
>> +#include "hw/xen/xen_backend.h"
>> +#include "monitor/qdev.h"
>> +#include "qapi/qmp/qbool.h"
>> +#include "qapi/qmp/qint.h"
>> +#include "qapi/qmp/qstring.h"
>> +#include "sys/user.h"
>> +
>> +#include 
>> +#include 
>> +
>> +#define TR(fmt, args...)\
>> +{   \
>> +struct timeval tv;  \
>> +\
>> +gettimeofday(, NULL);\
>> +fprintf(stderr, "%8ld.%06ld xen-usb(%s):" fmt, tv.tv_sec,   \
>> +tv.tv_usec, __func__, ##args);  \
>> +}
>> +#define TR_REQ(fmt, args...) { if (tr_debug & 1) TR(fmt, ##args) }
>> +#define TR_BUS(fmt, args...) { if (tr_debug & 2) TR(fmt, ##args) }
>> +
>> +#define USBBACK_MAXPORTSUSBIF_PIPE_PORT_MASK
>> +#define USBBACK_DEVNAME_SIZE32
> 
> That does not seem to be used
>> +#define USB_DEV_ADDR_SIZE   128
>> +
>> +struct usbif_ctrlrequest {
>> +uint8_tbRequestType;
>> +uint8_tbRequest;
>> +uint16_t   wValue;
>> +uint16_t   wIndex;
>> +uint16_t   wLength;
>> +};
> 
> Would it make sense to mention that this is part of the ABI?

It is part of the USB hardware interface. I'll add a comment.

> And if so perhaps a pointer where this in the Xen code base?
> 
>> +
>> +struct usbif_isoc_descriptor {
>> +uint32_t   offset;
>> +uint32_t   length;
>> +uint32_t   actual_length;
>> +int32_tstatus;
>> +};
> 
> Ditto?

ISOC code is remove from this patch, so I'll address this later.

> 
>> +
>> +struct usbback_info;
>> +struct usbback_req;
>> +
>> +struct usbback_stub {
>> +USBDevice  *dev;
>> +USBPortport;
>> +unsigned   speed;
> 
> unsigned int?

Okay.

>> +bool   attached;
>> +QTAILQ_HEAD(submit_q_head, usbback_req) submit_q;
>> +};
>> +
>> +struct usbback_req {
>> +struct usbback_info  *usbif;
>> +struct usbback_stub  *stub;
>> +struct usbif_urb_request req;
>> +USBPacketpacket;
>> +
>> +unsigned int nr_buffer_segs; /* # of transfer_buffer 
>> segments */
>> +unsigned int nr_extra_segs;  /* # of iso_frame_desc 
>> segments  */
>> +
>> +QTAILQ_ENTRY(usbback_req) q;
>> +
>> +void *buffer;
>> +void *isoc_buffer;
>> +struct libusb_transfer   *xfer;
>> +};
>> +
>> +struct usbback_info {
>> +struct 

Re: [Xen-devel] [Patch V1 3/3] xen: add pvUSB backend

[Konrad Rzeszutek Wilk]

On Thu, Sep 03, 2015 at 12:45:13PM +0200, Juergen Gross wrote:
> Add a backend for para-virtualized USB devices for xen domains.
> 
> The backend is using host-libusb to forward USB requests from a
> domain via libusb to the real device(s) passed through.
> 
> Signed-off-by: Juergen Gross 
> ---
>  hw/usb/Makefile.objs |4 +
>  hw/usb/xen-usb.c | 1120 
> ++
>  hw/xenpv/xen_machine_pv.c|3 +
>  include/hw/xen/xen_backend.h |   13 +-
>  4 files changed, 1137 insertions(+), 3 deletions(-)
>  create mode 100644 hw/usb/xen-usb.c
> 
> diff --git a/hw/usb/Makefile.objs b/hw/usb/Makefile.objs
> index 3fe4dff..0253184 100644
> --- a/hw/usb/Makefile.objs
> +++ b/hw/usb/Makefile.objs
> @@ -36,3 +36,7 @@ common-obj-$(CONFIG_USB_REDIR) += redirect.o quirks.o
>  
>  # usb pass-through
>  common-obj-y += $(patsubst %,host-%.o,$(HOST_USB))
> +
> +ifeq ($(CONFIG_USB_LIBUSB),y)
> +common-obj-$(CONFIG_XEN_BACKEND) += xen-usb.o
> +endif
> diff --git a/hw/usb/xen-usb.c b/hw/usb/xen-usb.c
> new file mode 100644
> index 000..2570bd7
> --- /dev/null
> +++ b/hw/usb/xen-usb.c
> @@ -0,0 +1,1120 @@
> +/*
> + *  xen paravirt usb device backend
> + *
> + *  (c) Juergen Gross 
> + *
> + *  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; under version 2 of the License.
> + *
> + *  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 .
> + *
> + *  Contributions after 2012-01-13 are licensed under the terms of the
> + *  GNU GPL, version 2 or (at your option) any later version.
> + */
> +
> +#include 
> +#include 
> +#include 
> +#include 
> +
> +#include "qemu-common.h"
> +#include "qemu/config-file.h"
> +#include "hw/sysbus.h"
> +#include "hw/usb.h"
> +#include "hw/xen/xen_backend.h"
> +#include "monitor/qdev.h"
> +#include "qapi/qmp/qbool.h"
> +#include "qapi/qmp/qint.h"
> +#include "qapi/qmp/qstring.h"
> +#include "sys/user.h"
> +
> +#include 
> +#include 
> +
> +#define TR(fmt, args...)\
> +{   \
> +struct timeval tv;  \
> +\
> +gettimeofday(, NULL);\
> +fprintf(stderr, "%8ld.%06ld xen-usb(%s):" fmt, tv.tv_sec,   \
> +tv.tv_usec, __func__, ##args);  \
> +}
> +#define TR_REQ(fmt, args...) { if (tr_debug & 1) TR(fmt, ##args) }
> +#define TR_BUS(fmt, args...) { if (tr_debug & 2) TR(fmt, ##args) }
> +
> +#define USBBACK_MAXPORTSUSBIF_PIPE_PORT_MASK
> +#define USBBACK_DEVNAME_SIZE32

That does not seem to be used
> +#define USB_DEV_ADDR_SIZE   128
> +
> +struct usbif_ctrlrequest {
> +uint8_tbRequestType;
> +uint8_tbRequest;
> +uint16_t   wValue;
> +uint16_t   wIndex;
> +uint16_t   wLength;
> +};

Would it make sense to mention that this is part of the ABI?
And if so perhaps a pointer where this in the Xen code base?

> +
> +struct usbif_isoc_descriptor {
> +uint32_t   offset;
> +uint32_t   length;
> +uint32_t   actual_length;
> +int32_tstatus;
> +};

Ditto?

> +
> +struct usbback_info;
> +struct usbback_req;
> +
> +struct usbback_stub {
> +USBDevice  *dev;
> +USBPortport;
> +unsigned   speed;

unsigned int?
> +bool   attached;
> +QTAILQ_HEAD(submit_q_head, usbback_req) submit_q;
> +};
> +
> +struct usbback_req {
> +struct usbback_info  *usbif;
> +struct usbback_stub  *stub;
> +struct usbif_urb_request req;
> +USBPacketpacket;
> +
> +unsigned int nr_buffer_segs; /* # of transfer_buffer 
> segments */
> +unsigned int nr_extra_segs;  /* # of iso_frame_desc segments 
>  */
> +
> +QTAILQ_ENTRY(usbback_req) q;
> +
> +void *buffer;
> +void *isoc_buffer;
> +struct libusb_transfer   *xfer;
> +};
> +
> +struct usbback_info {
> +struct XenDevice xendev;  /* must be first */
> +USBBus   bus;
> +void *urb_sring;
> +void *conn_sring;
> +struct usbif_urb_back_ring urb_ring;
> +struct usbif_conn_back_ring conn_ring;
> +int  num_ports;
> +int  usb_ver;
> +bool ring_error;
> +

Re: [Xen-devel] [Patch V1 3/3] xen: add pvUSB backend

[Stefano Stabellini]

On Wed, 9 Sep 2015, Juergen Gross wrote:
> On 09/07/2015 07:38 PM, Stefano Stabellini wrote:
> > On Thu, 3 Sep 2015, Juergen Gross wrote:
> > > Add a backend for para-virtualized USB devices for xen domains.
> > > 
> > > The backend is using host-libusb to forward USB requests from a
> > > domain via libusb to the real device(s) passed through.
> > > 
> > > Signed-off-by: Juergen Gross 
> > 
> > Aside from a few minor comments below, this looks pretty good from a Xen
> > perspective, however I am not too qualified to review the details of the
> > pvusb protocol or the way the requests are handled internally in QEMU.
> > 
> > I would be glad if Gerd could take a look at this too.
> > 
> > Juergen, if we commit this, would you be happy to maintain it going
> > forward?
> 
> Sure.
> 
> > > diff --git a/hw/usb/xen-usb.c b/hw/usb/xen-usb.c
> > > new file mode 100644
> > > index 000..2570bd7
> > > --- /dev/null
> > > +++ b/hw/usb/xen-usb.c
> ...
> > > +#define TR(fmt, args...)\
> > > +{   \
> > > +struct timeval tv;  \
> > > +\
> > > +gettimeofday(, NULL);\
> > > +fprintf(stderr, "%8ld.%06ld xen-usb(%s):" fmt, tv.tv_sec,   \
> > > +tv.tv_usec, __func__, ##args);  \
> > 
> > Please use xen_be_printf. I am not sure I would go as far as using
> > gettimeofday, but I can see it could be useful here.
> 
> Okay. I'll keep the time information as it has been proved to be really
> valuable.
> 
> > > +}
> > > +#define TR_REQ(fmt, args...) { if (tr_debug & 1) TR(fmt, ##args) }
> > > +#define TR_BUS(fmt, args...) { if (tr_debug & 2) TR(fmt, ##args) }
> > 
> > I would drop these and just use the loglevels of xen_be_printf.
> 
> Hmm, something like:
> 
> TR -> level 1
> TR_BUS -> level 2
> TR_REQ -> level 3
> 
> Is it possible to control trace levels per device?

Yes, with xendev->debug.


> If not, trying to
> catch an error requiring to trace on request level might be hard as
> concurrent qdisk trace entries could affect timing severely.
> 
> ...
> > > +static void xen_bus_child_detach(USBPort *port, USBDevice *child)
> > > +{
> > > +TR_BUS("called\n");
> > > +}
> > > +
> > > +static void xen_bus_complete(USBPort *port, USBPacket *packet)
> > > +{
> > > +TR_REQ("called\n");
> > 
> > Could you please either remove these debug messages or make them more
> > informative.
> 
> Which information are you missing? As long as the TR_* macros aren't
> changed they'll trace the function as well. In the context of other
> traces written they have been completely valuable.

I am saying that "called" is not very informative as a debug message,
you might as well remove it and rearrage the calls to be just:

TS_BUS();

But if you want to trace the call, maybe you could use the trace_*
framework?

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Re: [Xen-devel] [Patch V1 3/3] xen: add pvUSB backend

[Stefano Stabellini]

On Thu, 3 Sep 2015, Juergen Gross wrote:
> Add a backend for para-virtualized USB devices for xen domains.
> 
> The backend is using host-libusb to forward USB requests from a
> domain via libusb to the real device(s) passed through.
> 
> Signed-off-by: Juergen Gross 

Aside from a few minor comments below, this looks pretty good from a Xen
perspective, however I am not too qualified to review the details of the
pvusb protocol or the way the requests are handled internally in QEMU.

I would be glad if Gerd could take a look at this too.

Juergen, if we commit this, would you be happy to maintain it going
forward?


> diff --git a/hw/usb/Makefile.objs b/hw/usb/Makefile.objs
> index 3fe4dff..0253184 100644
> --- a/hw/usb/Makefile.objs
> +++ b/hw/usb/Makefile.objs
> @@ -36,3 +36,7 @@ common-obj-$(CONFIG_USB_REDIR) += redirect.o quirks.o
>  
>  # usb pass-through
>  common-obj-y += $(patsubst %,host-%.o,$(HOST_USB))
> +
> +ifeq ($(CONFIG_USB_LIBUSB),y)
> +common-obj-$(CONFIG_XEN_BACKEND) += xen-usb.o
> +endif
> diff --git a/hw/usb/xen-usb.c b/hw/usb/xen-usb.c
> new file mode 100644
> index 000..2570bd7
> --- /dev/null
> +++ b/hw/usb/xen-usb.c
> @@ -0,0 +1,1120 @@
> +/*
> + *  xen paravirt usb device backend
> + *
> + *  (c) Juergen Gross 
> + *
> + *  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; under version 2 of the License.
> + *
> + *  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 .
> + *
> + *  Contributions after 2012-01-13 are licensed under the terms of the
> + *  GNU GPL, version 2 or (at your option) any later version.
> + */
> +
> +#include 
> +#include 
> +#include 
> +#include 
> +
> +#include "qemu-common.h"
> +#include "qemu/config-file.h"
> +#include "hw/sysbus.h"
> +#include "hw/usb.h"
> +#include "hw/xen/xen_backend.h"
> +#include "monitor/qdev.h"
> +#include "qapi/qmp/qbool.h"
> +#include "qapi/qmp/qint.h"
> +#include "qapi/qmp/qstring.h"
> +#include "sys/user.h"
> +
> +#include 
> +#include 
> +
> +#define TR(fmt, args...)\
> +{   \
> +struct timeval tv;  \
> +\
> +gettimeofday(, NULL);\
> +fprintf(stderr, "%8ld.%06ld xen-usb(%s):" fmt, tv.tv_sec,   \
> +tv.tv_usec, __func__, ##args);  \

Please use xen_be_printf. I am not sure I would go as far as using
gettimeofday, but I can see it could be useful here.


> +}
> +#define TR_REQ(fmt, args...) { if (tr_debug & 1) TR(fmt, ##args) }
> +#define TR_BUS(fmt, args...) { if (tr_debug & 2) TR(fmt, ##args) }

I would drop these and just use the loglevels of xen_be_printf.


> +#define USBBACK_MAXPORTSUSBIF_PIPE_PORT_MASK
> +#define USBBACK_DEVNAME_SIZE32
> +#define USB_DEV_ADDR_SIZE   128
> +
> +struct usbif_ctrlrequest {
> +uint8_tbRequestType;
> +uint8_tbRequest;
> +uint16_t   wValue;
> +uint16_t   wIndex;
> +uint16_t   wLength;
> +};
> +
> +struct usbif_isoc_descriptor {
> +uint32_t   offset;
> +uint32_t   length;
> +uint32_t   actual_length;
> +int32_tstatus;
> +};
> +
> +struct usbback_info;
> +struct usbback_req;
> +
> +struct usbback_stub {
> +USBDevice  *dev;
> +USBPortport;
> +unsigned   speed;
> +bool   attached;
> +QTAILQ_HEAD(submit_q_head, usbback_req) submit_q;
> +};
> +
> +struct usbback_req {
> +struct usbback_info  *usbif;
> +struct usbback_stub  *stub;
> +struct usbif_urb_request req;
> +USBPacketpacket;
> +
> +unsigned int nr_buffer_segs; /* # of transfer_buffer 
> segments */
> +unsigned int nr_extra_segs;  /* # of iso_frame_desc segments 
>  */
> +
> +QTAILQ_ENTRY(usbback_req) q;
> +
> +void *buffer;
> +void *isoc_buffer;
> +struct libusb_transfer   *xfer;
> +};
> +
> +struct usbback_info {
> +struct XenDevice xendev;  /* must be first */
> +USBBus   bus;
> +void *urb_sring;
> +void *conn_sring;
> +struct usbif_urb_back_ring urb_ring;
> +struct usbif_conn_back_ring conn_ring;
> +int  num_ports;
> +int  usb_ver;
> +bool

[Xen-devel] [Patch V1 3/3] xen: add pvUSB backend

[Juergen Gross]

Add a backend for para-virtualized USB devices for xen domains.

The backend is using host-libusb to forward USB requests from a
domain via libusb to the real device(s) passed through.

Signed-off-by: Juergen Gross 
---
 hw/usb/Makefile.objs |4 +
 hw/usb/xen-usb.c | 1120 ++
 hw/xenpv/xen_machine_pv.c|3 +
 include/hw/xen/xen_backend.h |   13 +-
 4 files changed, 1137 insertions(+), 3 deletions(-)
 create mode 100644 hw/usb/xen-usb.c

diff --git a/hw/usb/Makefile.objs b/hw/usb/Makefile.objs
index 3fe4dff..0253184 100644
--- a/hw/usb/Makefile.objs
+++ b/hw/usb/Makefile.objs
@@ -36,3 +36,7 @@ common-obj-$(CONFIG_USB_REDIR) += redirect.o quirks.o
 
 # usb pass-through
 common-obj-y += $(patsubst %,host-%.o,$(HOST_USB))
+
+ifeq ($(CONFIG_USB_LIBUSB),y)
+common-obj-$(CONFIG_XEN_BACKEND) += xen-usb.o
+endif
diff --git a/hw/usb/xen-usb.c b/hw/usb/xen-usb.c
new file mode 100644
index 000..2570bd7
--- /dev/null
+++ b/hw/usb/xen-usb.c
@@ -0,0 +1,1120 @@
+/*
+ *  xen paravirt usb device backend
+ *
+ *  (c) Juergen Gross 
+ *
+ *  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; under version 2 of the License.
+ *
+ *  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 .
+ *
+ *  Contributions after 2012-01-13 are licensed under the terms of the
+ *  GNU GPL, version 2 or (at your option) any later version.
+ */
+
+#include 
+#include 
+#include 
+#include 
+
+#include "qemu-common.h"
+#include "qemu/config-file.h"
+#include "hw/sysbus.h"
+#include "hw/usb.h"
+#include "hw/xen/xen_backend.h"
+#include "monitor/qdev.h"
+#include "qapi/qmp/qbool.h"
+#include "qapi/qmp/qint.h"
+#include "qapi/qmp/qstring.h"
+#include "sys/user.h"
+
+#include 
+#include 
+
+#define TR(fmt, args...)\
+{   \
+struct timeval tv;  \
+\
+gettimeofday(, NULL);\
+fprintf(stderr, "%8ld.%06ld xen-usb(%s):" fmt, tv.tv_sec,   \
+tv.tv_usec, __func__, ##args);  \
+}
+#define TR_REQ(fmt, args...) { if (tr_debug & 1) TR(fmt, ##args) }
+#define TR_BUS(fmt, args...) { if (tr_debug & 2) TR(fmt, ##args) }
+
+#define USBBACK_MAXPORTSUSBIF_PIPE_PORT_MASK
+#define USBBACK_DEVNAME_SIZE32
+#define USB_DEV_ADDR_SIZE   128
+
+struct usbif_ctrlrequest {
+uint8_tbRequestType;
+uint8_tbRequest;
+uint16_t   wValue;
+uint16_t   wIndex;
+uint16_t   wLength;
+};
+
+struct usbif_isoc_descriptor {
+uint32_t   offset;
+uint32_t   length;
+uint32_t   actual_length;
+int32_tstatus;
+};
+
+struct usbback_info;
+struct usbback_req;
+
+struct usbback_stub {
+USBDevice  *dev;
+USBPortport;
+unsigned   speed;
+bool   attached;
+QTAILQ_HEAD(submit_q_head, usbback_req) submit_q;
+};
+
+struct usbback_req {
+struct usbback_info  *usbif;
+struct usbback_stub  *stub;
+struct usbif_urb_request req;
+USBPacketpacket;
+
+unsigned int nr_buffer_segs; /* # of transfer_buffer segments 
*/
+unsigned int nr_extra_segs;  /* # of iso_frame_desc segments  
*/
+
+QTAILQ_ENTRY(usbback_req) q;
+
+void *buffer;
+void *isoc_buffer;
+struct libusb_transfer   *xfer;
+};
+
+struct usbback_info {
+struct XenDevice xendev;  /* must be first */
+USBBus   bus;
+void *urb_sring;
+void *conn_sring;
+struct usbif_urb_back_ring urb_ring;
+struct usbif_conn_back_ring conn_ring;
+int  num_ports;
+int  usb_ver;
+bool ring_error;
+QTAILQ_HEAD(req_free_q_head, usbback_req) req_free_q;
+struct usbback_stub  ports[USBBACK_MAXPORTS];
+struct usbback_stub  *addr_table[USB_DEV_ADDR_SIZE];
+QEMUBH   *bh;
+};
+
+static unsigned int tr_debug = 3;
+
+static void usbback_copy_buffer(struct usbback_req *usbback_req,
+struct usbif_isoc_descriptor *iso, bool out,
+unsigned len, unsigned off)
+{
+struct usbif_request_segment *seg;
+unsigned s, offset, copy_len,