From: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
To: Tang Bin <tangbin@cmss.chinamobile.com>,
Greg KH <gregkh@linuxfoundation.org>
Cc: stern@rowland.harvard.edu, linux-usb@vger.kernel.org,
linux-kernel@vger.kernel.org,
Zhang Shengju <zhangshengju@cmss.chinamobile.com>
Subject: Re: [PATCH] USB: host: ehci: Add error handlinginehci_mxc_drv_probe()
Date: Fri, 8 May 2020 23:27:38 +0300 [thread overview]
Message-ID: <66a6bbca-4218-fb71-7284-37f73d5a3c58@cogentembedded.com> (raw)
In-Reply-To: <107353c0-09f2-858d-2a87-498e2d8584c6@cmss.chinamobile.com>
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@cmss.chinamobile.com>
>>>>> Signed-off-by: Tang Bin <tangbin@cmss.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 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
next prev parent reply other threads:[~2020-05-08 20:27 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-08 11:44 [PATCH] USB: host: ehci: Add error handling in ehci_mxc_drv_probe() Tang Bin
2020-05-08 11:48 ` Greg KH
2020-05-08 13:55 ` [PATCH] USB: host: ehci: Add error handling inehci_mxc_drv_probe() Tang Bin
2020-05-08 14:31 ` Greg KH
2020-05-08 15:03 ` [PATCH] USB: host: ehci: Add error handlinginehci_mxc_drv_probe() Tang Bin
2020-05-08 20:27 ` Sergei Shtylyov [this message]
2020-05-09 1:13 ` Tang Bin
2020-05-08 20:30 ` [PATCH] USB: host: ehci: Add error handling in ehci_mxc_drv_probe() Sergei Shtylyov
2020-05-08 13:51 ` Alan Stern
2020-05-13 12:55 ` Tang Bin
2020-05-13 13:01 ` Greg KH
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