linux-kernel - Re: [PATCHv2-next 3/3] serial_core: Remove unused member in uart

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Message-ID: <8f11e2fa-495d-fe25-f5e4-52c9580240d7@arista.com>
Date:   Tue, 14 Jan 2020 17:47:33 +0000
From:   Dmitry Safonov <dima@...sta.com>
To:     Joe Perches <joe@...ches.com>, linux-kernel@...r.kernel.org
Cc:     Dmitry Safonov <0x7f454c46@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        Jiri Slaby <jslaby@...e.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Vasiliy Khoruzhick <vasilykh@...sta.com>,
        linux-serial@...r.kernel.org
Subject: Re: [PATCHv2-next 3/3] serial_core: Remove unused member in uart_port

On 1/14/20 5:36 PM, Joe Perches wrote:
> On Tue, 2020-01-14 at 17:19 +0000, Dmitry Safonov wrote:
>> It should remove the align-padding before @name.
> []
>> diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
> []
>> @@ -247,7 +247,6 @@ struct uart_port {
>>  
>>  	unsigned char		hub6;			/* this should be in the 8250 driver */
>>  	unsigned char		suspended;
>> -	unsigned char		unused;
> 
> I suggest this not be applied as this is just to let
> readers know that there is an unused 1 byte alignment
> hole here that could be used for something else.

Heh, 2/3 adds another `unsigned char`, so the neighbours look like:

: unsigned long sysrq;		/* sysrq timeout */
: unsigned int	sysrq_ch;	/* char for sysrq */
: unsigned char	has_sysrq;
: unsigned char	sysrq_seq;	/* index in sysrq_toggle_seq */
:
: unsigned char	hub6;		/* this should be in the 8250 driver */
: unsigned char	suspended;
: unsigned char	unused;
: const char	*name;		/* port name */

So the hole became 4 bytes on 64-bit.

I can make it unused[4], but..

Separated the patch per Greg's review and I think it makes sense to have
it separately from 2/3 because last time I've touched it, it actually
was in use by drivers (regardless the name).

Thanks,
          Dmitry