linux-kernel - Re: [PATCH] USB: host: ehci: Add error handling inehci_mxc_drv

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Date:   Fri, 8 May 2020 16:31:10 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Tang Bin <tangbin@...s.chinamobile.com>
Cc:     stern@...land.harvard.edu, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Zhang Shengju <zhangshengju@...s.chinamobile.com>
Subject: Re: [PATCH] USB: host: ehci: Add error handling
 inehci_mxc_drv_probe()

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@...s.chinamobile.com>
> > > Signed-off-by: Tang Bin <tangbin@...s.chinamobile.com>
> > > ---
> > >   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'， the function platform_get_irq() is
> explained and used as follows:
> 
>      * Gets an IRQ for a platform device and prints an error message if
> finding the
>      * IRQ fails. Device drivers should check the return value for errors so
> as to
>      * not pass a negative integer value to the request_irq() APIs.
>      *
>      * Example:
>      *        int irq = platform_get_irq(pdev, 0);
>      *        if (irq < 0)
>      *            return irq;
>      *
>      * 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.

thanks,

greg k-h