linux-kernel - Re: [PATCH v2] usbip: convert to use faux

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Message-ID: <2025062010-hardiness-flashily-cb0f@gregkh>
Date: Fri, 20 Jun 2025 06:29:36 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Zongmin Zhou <min_halo@....com>
Cc: shuah@...nel.org, valentina.manea.m@...il.com, i@...ithal.me,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
	zhouzongmin@...inos.cn
Subject: Re: [PATCH v2] usbip: convert to use faux_device

On Fri, Jun 20, 2025 at 10:16:16AM +0800, Zongmin Zhou wrote:
> 
> On 2025/6/19 19:01, Greg KH wrote:
> > On Wed, Jun 04, 2025 at 02:54:10PM +0800, Zongmin Zhou wrote:
> > > From: Zongmin Zhou <zhouzongmin@...inos.cn>
> > > 
> > > The vhci driver does not need to create a platform device,
> > > it only did so because it was simple to do that in order to
> > > get a place in sysfs to hang some device-specific attributes.
> > > Now the faux device interface is more appropriate,change it
> > > over to use the faux bus instead.
> > > 
> > > Signed-off-by: Zongmin Zhou <zhouzongmin@...inos.cn>
> > > ---
> > > Changes in v2:
> > > - don't change faux create api,just call probe on vhci_hcd_init.
> > > 
> > >   drivers/usb/usbip/vhci.h             |  4 +-
> > >   drivers/usb/usbip/vhci_hcd.c         | 86 +++++++++++-----------------
> > >   drivers/usb/usbip/vhci_sysfs.c       | 68 +++++++++++-----------
> > >   tools/usb/usbip/libsrc/vhci_driver.h |  2 +-
> > >   4 files changed, 72 insertions(+), 88 deletions(-)
> > I get the following build errors from this patch:
> > 
> > drivers/usb/usbip/vhci_hcd.c:1462:12: error: ‘vhci_hcd_resume’ defined but not used [-Werror=unused-function]
> >   1462 | static int vhci_hcd_resume(struct faux_device *fdev)
> >        |            ^~~~~~~~~~~~~~~
> > drivers/usb/usbip/vhci_hcd.c:1418:12: error: ‘vhci_hcd_suspend’ defined but not used [-Werror=unused-function]
> >   1418 | static int vhci_hcd_suspend(struct faux_device *fdev, pm_message_t state)
> >        |            ^~~~~~~~~~~~~~~~
> > cc1: all warnings being treated as errors
> > 
> > Are you sure you tested this?
> I apologize for not enabling -Werror, which resulted in missing this error
> warning.
> I have tested usbip feature use the new patch,but not test system
> suspend/resume.
> The faux bus type don't add pm function,and vhci-hcd driver can't register
> it.
> Maybe have to add suspend/resume for it.like below:
> static const struct bus_type faux_bus_type = {
>     .name        = "faux",
>     .match        = faux_match,
>     .probe        = faux_probe,
>     .remove        = faux_remove,
>     .resume     = faux_resume,
>     .suspend    = faux_suspend,
> };
> 
> Is that right?
> Your expertise would be greatly valued.

As this is not real hardware, why do you need the suspend/resume
callbacks at all?  What is happening here that requires them?

thanks,

greg k-h