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

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Message-ID: <fb147bdf-faaa-8919-407e-89b4fe1337a6@cmss.chinamobile.com>
Date:   Fri, 8 May 2020 21:55:53 +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 handling
 inehci_mxc_drv_probe()

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.

Thanks for your patience and replay.

Tang Bin