linux-kernel - Re: [PATCH] tty: omap-serial: remove set but unused variable

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Date:   Thu, 5 Dec 2019 13:39:58 +0100
From:   Jiri Slaby <jslaby@...e.com>
To:     Xiongfeng Wang <wangxiongfeng2@...wei.com>,
        Greg KH <gregkh@...uxfoundation.org>
Cc:     linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        huawei.libin@...wei.com, shubhrajyoti@...com,
        "balbi@...com >> Felipe Balbi" <balbi@...com>
Subject: Re: [PATCH] tty: omap-serial: remove set but unused variable

On 05. 12. 19, 13:30, Xiongfeng Wang wrote:
> 
> 
> On 2019/12/5 20:13, Greg KH wrote:
>> On Thu, Dec 05, 2019 at 08:04:36PM +0800, Xiongfeng Wang wrote:
>>> Fix the following warning:
>>> drivers/tty/serial/omap-serial.c: In function serial_omap_rlsi:
>>> drivers/tty/serial/omap-serial.c:496:16: warning: variable ch set but not used [-Wunused-but-set-variable]
>>>
>>> Reported-by: Hulk Robot <hulkci@...wei.com>
>>> Signed-off-by: Xiongfeng Wang <wangxiongfeng2@...wei.com>
>>> ---
>>>  drivers/tty/serial/omap-serial.c | 3 +--
>>>  1 file changed, 1 insertion(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
>>> index 6420ae5..54ee3ae 100644
>>> --- a/drivers/tty/serial/omap-serial.c
>>> +++ b/drivers/tty/serial/omap-serial.c
>>> @@ -493,10 +493,9 @@ static unsigned int check_modem_status(struct uart_omap_port *up)
>>>  static void serial_omap_rlsi(struct uart_omap_port *up, unsigned int lsr)
>>>  {
>>>  	unsigned int flag;
>>> -	unsigned char ch = 0;
>>>  
>>>  	if (likely(lsr & UART_LSR_DR))
>>> -		ch = serial_in(up, UART_RX);
>>> +		serial_in(up, UART_RX);
>>
>> Shouldn't you be doing something with 'ch'?
> 
> Sorry, my original thought is trying not to modify the existing logic.
> I will look into the mechanism to see if I need to check 'ch'.

The change looks in fact correct, see:
commit 9a12fcf8b1543c99ffcec3d61db86f0dea52dc9d
Author: Shubhrajyoti D <shubhrajyoti@...com>
Date:   Fri Sep 21 20:07:19 2012 +0530

    serial: omap: fix the reciever line error case

It also says: "This is recommended in the interrupt reset method in the
table 23-246 of the omap4 TRM."

The character read is erroneous and should be apparently dropped. But
you should add a comment about it, though.

thanks,
-- 
js
suse labs