On 05/08/2020 06:03 PM, Tang Bin 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'， 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 thought I did that already couple years ago, when returned 0 from platform_get_irq() could mean both IRQ # and error... :-)
>
> 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;
And you then return 0 (success) as if your probe() succeeded. Congratulations! :-P
>
> Thanks,
>
> Tang Bin
MBR, Sergei
