linux-kernel - Re: [PATCH -next] usb: ftdi-elan: Fix if == else warnings in ftdi_elan_respond

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Date:   Wed, 23 Jan 2019 21:55:53 +0800
From:   YueHaibing <yuehaibing@...wei.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-usb@...r.kernel.org>
Subject: Re: [PATCH -next] usb: ftdi-elan: Fix if == else warnings in
 ftdi_elan_respond_engine

On 2019/1/23 21:41, Greg KH wrote:
> On Wed, Jan 23, 2019 at 09:17:38PM +0800, YueHaibing wrote:
>> On 2019/1/23 20:43, Greg KH wrote:
>>> On Wed, Jan 23, 2019 at 08:34:42PM +0800, YueHaibing wrote:
>>>> ./drivers/usb/misc/ftdi-elan.c:972:10-12: WARNING: possible condition with no effect (if == else)
>>>> ./drivers/usb/misc/ftdi-elan.c:983:9-11: WARNING: possible condition with no effect (if == else)
>>>> ./drivers/usb/misc/ftdi-elan.c:2052:11-13: WARNING: possible condition with no effect (if == else)
>>>>
>>>> Signed-off-by: YueHaibing <yuehaibing@...wei.com>
>>>
>>> You can not just provide the output of a tool as a changelog text,
>>> sorry.
>>>
>>> Please explain what those lines mean, and why you are making the change
>>> that you are.
>>
>> ok, will do that.
>>
>>>
>>>> ---
>>>>  drivers/usb/misc/ftdi-elan.c | 26 --------------------------
>>>>  1 file changed, 26 deletions(-)
>>>>
>>>> diff --git a/drivers/usb/misc/ftdi-elan.c b/drivers/usb/misc/ftdi-elan.c
>>>> index 76c718a..257efac 100644
>>>> --- a/drivers/usb/misc/ftdi-elan.c
>>>> +++ b/drivers/usb/misc/ftdi-elan.c
>>>> @@ -915,7 +915,6 @@ static int ftdi_elan_respond_engine(struct usb_ftdi *ftdi)
>>>>  	int bytes_read = 0;
>>>>  	int retry_on_empty = 1;
>>>>  	int retry_on_timeout = 3;
>>>> -	int empty_packets = 0;
>>>>  read:{
>>>>  		int packet_bytes = 0;
>>>>  		int retval = usb_bulk_msg(ftdi->udev,
>>>> @@ -960,31 +959,6 @@ read:{
>>>>  			dev_err(&ftdi->udev->dev, "error = %d with packet_bytes = %d with total %d bytes%s\n",
>>>>  				retval, packet_bytes, bytes_read, diag);
>>>>  			return retval;
>>>> -		} else if (packet_bytes == 2) {
>>>> -			unsigned char s0 = ftdi->bulk_in_buffer[0];
>>>> -			unsigned char s1 = ftdi->bulk_in_buffer[1];
>>>> -			empty_packets += 1;
>>>> -			if (s0 == 0x31 && s1 == 0x60) {
>>>> -				if (retry_on_empty-- > 0) {
>>>> -					goto more;
>>>> -				} else
>>>> -					return 0;
>>>> -			} else if (s0 == 0x31 && s1 == 0x00) {
>>>> -				if (retry_on_empty-- > 0) {
>>>> -					goto more;
>>>> -				} else
>>>> -					return 0;
>>>> -			} else {
>>>> -				if (retry_on_empty-- > 0) {
>>>> -					goto more;
>>>> -				} else
>>>> -					return 0;
>>>> -			}
>>>> -		} else if (packet_bytes == 1) {
>>>> -			if (retry_on_empty-- > 0) {
>>>> -				goto more;
>>>> -			} else
>>>> -				return 0;
>>>
>>> Are you _sure_ that these lines are not needed and that the compiler is
>>> not really seeing them?  As it doesn't look that way to me, what am I
>>> missing?
>>
>> I checked and make sure that All these if/else if branch just do the same thing:
>>
>> 	if (retry_on_empty-- > 0) {
>> 		goto more;
>> 	} else
>> 		return 0;
>>
>> so it can be merged into the last else branch.
>>
>> Also the variable 'empty_packets' doesn't use in any place, except for self increment
> 
> Don't do two different things in the same patch :)

Thanks, I will split it into two.

> 
> 
> .
>