linux-kernel - Re: [PATCH 1/2] usbip: Remove repeated setting of hcd->state in vhci_bus

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Message-ID: <20190507154918.GA2427@localhost.localdomain>
Date:   Wed, 8 May 2019 00:49:19 +0900
From:   Suwan Kim <suwan.kim027@...il.com>
To:     shuah <shuah@...nel.org>
Cc:     valentina.manea.m@...il.com, gregkh@...uxfoundation.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] usbip: Remove repeated setting of hcd->state in
 vhci_bus_suspend()

Hi Shuah,

On Mon, May 06, 2019 at 09:13:02AM -0600, shuah wrote:
> On 5/6/19 6:55 AM, Suwan Kim wrote:
> > When hcd suspends execution, hcd_bus_suspend() calls vhci_bus_suspend()
> > which sets hcd->state as HC_STATE_SUSPENDED. But after calling
> > vhci_bus_suspend(), hcd_bus_suspend() also sets hcd->state as
> > HC_STATE_SUSPENDED.
> > So, setting hcd->state in vhci_hcd_suspend() is unnecessary.
> > 
> > Signed-off-by: Suwan Kim <suwan.kim027@...il.com>
> > ---
> >   drivers/usb/usbip/vhci_hcd.c | 4 ----
> >   1 file changed, 4 deletions(-)
> > 
> > diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
> > index 667d9c0ec905..e6f378d00fb6 100644
> > --- a/drivers/usb/usbip/vhci_hcd.c
> > +++ b/drivers/usb/usbip/vhci_hcd.c
> > @@ -1238,10 +1238,6 @@ static int vhci_bus_suspend(struct usb_hcd *hcd)
> >   	dev_dbg(&hcd->self.root_hub->dev, "%s\n", __func__);
> > -	spin_lock_irqsave(&vhci->lock, flags);
> > -	hcd->state = HC_STATE_SUSPENDED;
> > -	spin_unlock_irqrestore(&vhci->lock, flags);
> > -
> >   	return 0;
> >   }
> > 
> 
> Tell me more about why you think this change is needed? How did you test
> this change?

I think that host controller specific functions, vhci_bus_resume()
or vhci_bus_suspend() in the case of vhci, usually process host
controller specific data (struct vhci_hcd) not a generic data
(struct usb_hcd). The generic data is usually processed by generic HCD
layer. But vhci_bus_resume() and vhci_bus_suspend() set generic data
(hcd->state) and moreover this variable is set in generic HCD layer
once again(hcd_bus_resume() and hcd_bus_suspend()).

So, i think host controller specific functions (vhci_bus_resume()
and vhci_bus_suspend()) don't need to set the generic data that is
"hcd->state = HC_STATE_RUNNING or HC_STATE_SUSPEND".

For test, I loaded vhci-hcd module, suspended and resumed my computer
and checked hcd->state variable. There is no difference compared with
not modified version because my patch just removes repeated and
unnecessary part.

Regards

Suwan Kim