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Subject: Re: [PATCH v3] checkpatch: add fix option for
 ASSIGNMENT_CONTINUATIONS
To:     Joe Perches <joe@perches.com>
Cc:     linux-kernel-mentees@lists.linuxfoundation.org,
        linux-kernel@vger.kernel.org, lukas.bulwahn@gmail.com
References: <20201117171856.13284-1-yashsri421@gmail.com>
 <48f56f40-a365-faac-542d-0e120fcf4365@gmail.com>
 <08f164e93dc40e066e81c4021485d27d5ad5a6b7.camel@perches.com>
From:   Aditya <yashsri421@gmail.com>
Message-ID: <6deacf63-a80f-67b5-0594-e5cb5e82f42b@gmail.com>
Date:   Fri, 20 Nov 2020 23:32:16 +0530
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On 20/11/20 10:56 pm, Joe Perches wrote:
> On Fri, 2020-11-20 at 16:11 +0530, Aditya wrote:
>> On 17/11/20 10:48 pm, Aditya Srivastava wrote:
>>> Currently, checkpatch warns us if an assignment operator is placed
>>> at the start of a line and not at the end of previous line.
>>>
>>> E.g., running checkpatch on commit 8195b1396ec8 ("hv_netvsc: fix
>>> deadlock on hotplug") reports:
>>>
>>> CHECK: Assignment operator '=' should be on the previous line
>>> +	struct netvsc_device *nvdev
>>> +		= container_of(w, struct netvsc_device, subchan_work);
>>>
>>> Provide a simple fix by appending assignment operator to the previous
>>> line and removing from the current line, if both the lines are additions
>>> (ie start with '+')
>>>
>>> Signed-off-by: Aditya Srivastava <yashsri421@gmail.com>
>>> ---
>>> Changes in v2:
>>> add check if both the lines are additions (ie start with '+')
>>>
>>> Changes in v3:
>>> quote $operator; test with division assignment operator ('/=')
>>>
>>>  scripts/checkpatch.pl | 10 ++++++++--
>>>  1 file changed, 8 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
>>> index c9aaaa443265..d5bc4d8e4f6c 100755
>>> --- a/scripts/checkpatch.pl
>>> +++ b/scripts/checkpatch.pl
>>> @@ -3542,8 +3542,14 @@ sub process {
>>>  
>>>
>>>  # check for assignments on the start of a line
>>>  		if ($sline =~ /^\+\s+($Assignment)[^=]/) {
>>> -			CHK("ASSIGNMENT_CONTINUATIONS",
>>> -			    "Assignment operator '$1' should be on the previous line\n" . $hereprev);
>>> +			my $operator = "$1";
>>> +			if (CHK("ASSIGNMENT_CONTINUATIONS",
>>> +				"Assignment operator '$1' should be on the previous line\n" . $hereprev) &&
>>> +			    $fix && $prevrawline =~ /^\+/) {
>>> +				# add assignment operator to the previous line, remove from current line
>>> +				$fixed[$fixlinenr - 1] .= " $operator";
>>> +				$fixed[$fixlinenr] =~ s/$operator\s*//;
>>> +			}
>>>  		}
>>>  
>>>
>>>  # check for && or || at the start of a line
>>>
>>
>> Hi Joe
>> This patch probably got missed. Please review :)
> 
> Did you look at $Assignment?  Did you see it can be /= ?
> 

Yes, I tested the patch with '/=' operator as well.
As I could not find any occurrences in the past(over 4.13..5.8), I
created an example for myself by modifying the above mentioned commit
example i.e. commit 8195b1396ec8 ("hv_netvsc: fix deadlock on
hotplug") as:

+	struct netvsc_device *nvdev
+		/= container_of(w, struct netvsc_device, subchan_work);

[For Line 144 and 145(where the warning was reported for '=' earlier)]

The fix changes these lines to:
+	struct netvsc_device *nvdev /=
+		container_of(w, struct netvsc_device, subchan_work);

On retesting the patch with checkpatch.pl, it did not give this CHECK,
nor did we add any new warning/error.

> If it is, what happens in the $fixed[$fixlinenr] line?
>

In $fixed[$fixlinenr], we are just getting rid of the operator and any
space(s) following it.

What do you think?

Thanks
Aditya