linux-kernel - Re: [PATCH v2] usb: dwc3: host: remove dead code in dwc3_host_get

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Message-ID: <181feb34-c46d-cadb-ad20-46074a53b4c9@suse.com>
Date:   Thu, 23 Mar 2023 14:48:56 +0100
From:   Oliver Neukum <oneukum@...e.com>
To:     Dan Carpenter <error27@...il.com>, Oliver Neukum <oneukum@...e.com>
Cc:     Sergei Shtylyov <sergei.shtylyov@...il.com>,
        Mingxuan Xiang <mx_xiang@...t.edu.cn>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        hust-os-kernel-patches@...glegroups.com,
        Dongliang Mu <dzm91@...t.edu.cn>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] usb: dwc3: host: remove dead code in
 dwc3_host_get_irq()

On 23.03.23 12:13, Dan Carpenter wrote:

>>>> v1->v2: remove redundant goto
>>>>    drivers/usb/dwc3/host.c | 4 ----
>>>>    1 file changed, 4 deletions(-)
>>>>
>>>> diff --git a/drivers/usb/dwc3/host.c b/drivers/usb/dwc3/host.c
>>>> index f6f13e7f1ba1..ca1e8294e835 100644
>>>> --- a/drivers/usb/dwc3/host.c
>>>> +++ b/drivers/usb/dwc3/host.c
>>>> @@ -54,12 +54,8 @@ static int dwc3_host_get_irq(struct dwc3 *dwc)
>>>>    	irq = platform_get_irq(dwc3_pdev, 0);
>>>>    	if (irq > 0) {
>>>>    		dwc3_host_fill_xhci_irq_res(dwc, irq, NULL);
>>>> -		goto out;
>>>>    	}
>>>
>>>      Now drop {} please. :-)
>>
>> Well, no, please drop the whole patch.
>> If platform_get_irq() returns -EPROBE_DEFER you now give that
>> as a return value.
>>
>> This tiny bit of optimization is not worth changing semantics.
> 
> The v2 patch doesn't change the semantics.  Mine did though...

Now I may be dense, but let's look at the current code:

         irq = platform_get_irq(dwc3_pdev, 0);

assuming irq = -EPROBE_DEFER

         if (irq > 0) {

not taken
                 dwc3_host_fill_xhci_irq_res(dwc, irq, NULL);
                 goto out;
         }

         if (!irq)

irq != 0
                 irq = -EINVAL;

out:
         return irq;

returning -EINVAL

Patched version:

         irq = platform_get_irq(dwc3_pdev, 0);

assuming irq = -EPROBE_DEFER

         if (irq > 0) {
                 dwc3_host_fill_xhci_irq_res(dwc, irq, NULL);
         }

out:
         return irq;

returning -EPROBE_DEFER

Your version:

  	irq = platform_get_irq(dwc3_pdev, 0);

assuming irq = -EPROBE_DEFER

  	if (irq > 0) {

not taken
  		dwc3_host_fill_xhci_irq_res(dwc, irq, NULL);
+		return irq;
  	}
  
+	return -ENODEV;

Yet another error return.
Now, I admit I am by now sufficiently confused to know which version is
correct, but they are all three different in what they return.

	Regards
		Oliver