Re: [PATCH] USB: host: ehci: Add error handlinginehci_mxc_drv_probe()

[Tang Bin]

On 2020/5/8 22:31, Greg KH wrote:
> On Fri, May 08, 2020 at 09:55:53PM +0800, Tang Bin wrote:
> > Hi, Greg:
> >
> > On 2020/5/8 19:48, Greg KH wrote:
> > > On Fri, May 08, 2020 at 07:44:53PM +0800, Tang Bin wrote:
> > > > The function ehci_mxc_drv_probe() does not perform sufficient error
> > > > checking after executing platform_get_irq(), thus fix it.
> > > >
> > > > Fixes: 7e8d5cd93fa ("USB: Add EHCI support for MX27 and MX31 based boards")
> > > > Signed-off-by: Zhang Shengju <zhangshengju@xxxxxxxxxxxxxxxxxxxx>
> > > > Signed-off-by: Tang Bin <tangbin@xxxxxxxxxxxxxxxxxxxx>
> > > > ---
> > > >    drivers/usb/host/ehci-mxc.c | 2 ++
> > > >    1 file changed, 2 insertions(+)
> > > >
> > > > diff --git a/drivers/usb/host/ehci-mxc.c b/drivers/usb/host/ehci-mxc.c
> > > > index a1eb5ee77..a0b42ba59 100644
> > > > --- a/drivers/usb/host/ehci-mxc.c
> > > > +++ b/drivers/usb/host/ehci-mxc.c
> > > > @@ -50,6 +50,8 @@ static int ehci_mxc_drv_probe(struct platform_device *pdev)
> > > >    	}
> > > >    	irq = platform_get_irq(pdev, 0);
> > > > +	if (irq < 0)
> > > > +		return irq;
> > > <= ?
> > In the file 'drivers/base/platform.c'ï the function platform_get_irq() is
> > explained and used as follows:
> >
> >  ÂÂÂÂ * Gets an IRQ for a platform device and prints an error message if
> > finding the
> >  ÂÂÂÂ * IRQ fails. Device drivers should check the return value for errors so
> > as to
> >  ÂÂÂÂ * not pass a negative integer value to the request_irq() APIs.
> >  ÂÂÂÂ *
> >  ÂÂÂÂ * Example:
> >  ÂÂÂÂ *ÂÂÂ ÂÂÂ int irq = platform_get_irq(pdev, 0);
> >  ÂÂÂÂ *ÂÂÂ ÂÂÂ if (irq < 0)
> >  ÂÂÂÂ *ÂÂÂ ÂÂÂ ÂÂÂ return irq;
> >  ÂÂÂÂ *
> >  ÂÂÂÂ * Return: IRQ number on success, negative error number on failure.
> >
> > And in my hardware experiment, even if I set the irq failed deliberately in
> > the DTS, the returned value is negative instead of zero.
> Please read the thread at
> 	https://lore.kernel.org/r/20200501224042.141366-1-helgaas%40kernel.org
> for more details about this.
Great, It looks beautiful, finally someone took a knife to the file 
'platform.c'.

I have been studied this place for a long time, and don't know what 
platform can return 0, which made me curious.

So the example should be:

ÂÂÂÂ *ÂÂÂ ÂÂÂ int irq = platform_get_irq(pdev, 0);
ÂÂÂÂ *ÂÂÂ ÂÂÂ if (irq <= 0)
ÂÂÂÂ *ÂÂÂ ÂÂÂ ÂÂÂ return irq;

Thanks,

Tang Bin