Re: [PATCH v2] usbip: tools: Add usbip host driver availability check

[Zongmin Zhou]

On 2026/3/25 16:58, Greg KH wrote:
> On Wed, Mar 25, 2026 at 10:26:34AM +0800, Zongmin Zhou wrote:
> > From: Zongmin Zhou <zhouzongmin@xxxxxxxxxx>
> >
> > Currently, usbip_generic_driver_open() doesn't verify that the required
> > kernel module (usbip-host or usbip-vudc) is actually loaded.
> > The function returns success even when no driver is present,
> > leading to usbipd daemon run success without driver loaded.
> >
> > So add a check function to ensure usbip host driver has been loaded.
> >
> > Suggested-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Zongmin Zhou <zhouzongmin@xxxxxxxxxx>
> > ---
> > Changes in v2:
> > - Use system calls directly instead of checking sysfs dir.
> >
> >   tools/usb/usbip/libsrc/usbip_device_driver.c | 7 +++++--
> >   tools/usb/usbip/libsrc/usbip_host_driver.c   | 8 ++++++--
> >   2 files changed, 11 insertions(+), 4 deletions(-)
> >
> > diff --git a/tools/usb/usbip/libsrc/usbip_device_driver.c b/tools/usb/usbip/libsrc/usbip_device_driver.c
> > index 927a151fa9aa..45ab647ef241 100644
> > --- a/tools/usb/usbip/libsrc/usbip_device_driver.c
> > +++ b/tools/usb/usbip/libsrc/usbip_device_driver.c
> > @@ -136,10 +136,13 @@ static int usbip_device_driver_open(struct usbip_host_driver *hdriver)
> >   	hdriver->ndevs = 0;
> >   	INIT_LIST_HEAD(&hdriver->edev_list);
> >   
> > -	ret = usbip_generic_driver_open(hdriver);
> > -	if (ret)
> > +	if (system("/sbin/lsmod | grep -q usbip_vudc")){
> What happens if the module is built into the kernel?
>
> >   		err("please load " USBIP_CORE_MOD_NAME ".ko and "
> >   		    USBIP_DEVICE_DRV_NAME ".ko!");
> > +		return -1;
> > +	}
> > +
> > +	ret = usbip_generic_driver_open(hdriver);
> >   
> >   	return ret;
> >   }
> > diff --git a/tools/usb/usbip/libsrc/usbip_host_driver.c b/tools/usb/usbip/libsrc/usbip_host_driver.c
> > index 573e73ec36bd..f0ac941d4f6e 100644
> > --- a/tools/usb/usbip/libsrc/usbip_host_driver.c
> > +++ b/tools/usb/usbip/libsrc/usbip_host_driver.c
> > @@ -31,10 +31,14 @@ static int usbip_host_driver_open(struct usbip_host_driver *hdriver)
> >   	hdriver->ndevs = 0;
> >   	INIT_LIST_HEAD(&hdriver->edev_list);
> >   
> > -	ret = usbip_generic_driver_open(hdriver);
> > -	if (ret)
> > +	if (system("/sbin/lsmod | grep -q usbip_host")){
> Same here, what happens if it is built in?
Thank you for pointing this out.
I apologize for not considering the built-in module case.

You are right that using lsmod | grep would incorrectly fail when 
usbip_host is built into the kernel (CONFIG_USBIP_HOST=y).
Usbip has always been built as a loadable module (.ko) by default, which 
led to this oversight.

To address this issue, would the following approach be acceptable?
1. Uses /sys/module/usbip_host to check wehther had been loaded, which 
exists for both loadable modules and built-in drivers.
2. Attempts to load the module via modprobe if it is not already loaded.

for example:
static int probe_usbip_host_driver(void)
{
     struct stat st;
     return !stat("/sys/module/usbip_host", &st);
}

static int usbip_host_driver_open(struct usbip_host_driver *hdriver)
{
     // 1. Check if driver is already loaded/built-in
     if (!probe_usbip_host_driver()) {
         // 2. Try to load the module
         system("/sbin/modprobe usbip-host > /dev/null 2>&1");
        // 3. Check again
          if (!probe_usbip_host_driver()) {
              err("please load " USBIP_CORE_MOD_NAME ".ko and "
                  USBIP_HOST_DRV_NAME ".ko!");
              return -1;
}
}

      // Continue with normal flow...
      ret = usbip_generic_driver_open(hdriver);
      return ret;
}

Does this look reasonable to you? I would be happy to submit a v3 patch 
with this approach if you agree.
> thanks,
>
> greg k-h