linux-kernel - Re: [PATCH] net: adaptec: remove dead code in set_vlan

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Message-ID: <fe835089-3499-0d70-304e-cc3d2e58a8d8@badula.org>
Date:   Fri, 20 Nov 2020 18:41:03 -0500
From:   Ion Badulescu <ionut@...ula.org>
To:     Jakub Kicinski <kuba@...nel.org>, xiakaixu1987@...il.com
Cc:     leon@...nel.org, davem@...emloft.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Kaixu Xia <kaixuxia@...cent.com>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH] net: adaptec: remove dead code in set_vlan_mode

On 11/20/20 6:17 PM, Jakub Kicinski wrote:
> On Fri, 20 Nov 2020 15:50:00 +0800 xiakaixu1987@...il.com wrote:
>> From: Kaixu Xia <kaixuxia@...cent.com>
>>
>> The body of the if statement can be executed only when the variable
>> vlan_count equals to 32, so the condition of the while statement can
>> not be true and the while statement is dead code. Remove it.
>>
>> Reported-by: Tosk Robot <tencent_os_robot@...cent.com>
>> Signed-off-by: Kaixu Xia <kaixuxia@...cent.com>
>> ---
>>   drivers/net/ethernet/adaptec/starfire.c | 9 ++-------
>>   1 file changed, 2 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/adaptec/starfire.c b/drivers/net/ethernet/adaptec/starfire.c
>> index 555299737b51..ad27a9fa5e95 100644
>> --- a/drivers/net/ethernet/adaptec/starfire.c
>> +++ b/drivers/net/ethernet/adaptec/starfire.c
>> @@ -1754,14 +1754,9 @@ static u32 set_vlan_mode(struct netdev_private *np)
>>   		filter_addr += 16;
>>   		vlan_count++;
>>   	}
>> -	if (vlan_count == 32) {
>> +	if (vlan_count == 32)
>>   		ret |= PerfectFilterVlan;
>> -		while (vlan_count < 32) {
>> -			writew(0, filter_addr);
>> -			filter_addr += 16;
>> -			vlan_count++;
>> -		}
>> -	}
>> +
>>   	return ret;
>>   }
>>   #endif /* VLAN_SUPPORT */
> 
> This got broken back in 2011:
> 
> commit 5da96be53a16a62488316810d0c7c5d58ce3ee4f
> Author: Jiri Pirko <jpirko@...hat.com>
> Date:   Wed Jul 20 04:54:31 2011 +0000
> 
>      starfire: do vlan cleanup
>      
>      - unify vlan and nonvlan rx path
>      - kill np->vlgrp and netdev_vlan_rx_register
>      
>      Signed-off-by: Jiri Pirko <jpirko@...hat.com>
>      Signed-off-by: David S. Miller <davem@...emloft.net>
> 
> The comparison to 32 was on a different variable before that change.
> 
> Ion, do you think anyone is still using this driver?
> 
> Maybe it's time we put it in the history book (by which I mean remove
> from the kernel).

Frankly, no, I don't know of any users, and that unfortunately includes 
myself. I still have two cards in my stash, but they're 64-bit PCI-X, so 
plugging them in would likely require taking a dremel to a 32-bit PCI 
slot to make it open-ended. (They do work in a 32-bit slot.)

Anyway, that filter code could use some fixing in other regards. So 
either we fix it properly (which I can submit a patch for), or clean it 
out for good.

-Ion