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

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Date:   Fri, 8 May 2020 23:03:27 +0800
From:   Tang Bin <tangbin@...s.chinamobile.com>
To:     Greg KH <gregkh@...uxfoundation.org>
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 handlinginehci_mxc_drv_probe()


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@...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.
>
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:

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

Thanks,

Tang Bin