linux-kernel - Re: [PATCH] RS485: fix inconsistencies in the meaning of some variables

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Date:	Sun, 13 Nov 2011 22:53:18 +0100
From:	Wolfram Sang <w.sang@...gutronix.de>
To:	Claudio Scordino <claudio@...dence.eu.com>
Cc:	Greg KH <greg@...ah.com>, Alan Cox <alan@...rguk.ukuu.org.uk>,
	Nicolas Ferre <nicolas.ferre@...el.com>, alan@...ux.intel.com,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Jesper Nilsson <Jesper.Nilsson@...s.com>,
	Mikael Starvik <mikael.starvik@...s.com>,
	Darron Black <darron@...ffin.net>
Subject: Re: [PATCH] RS485: fix inconsistencies in the meaning of some
 variables

Hi,

I have been working on a patch series which adds hardware RS485 to the 8250
according to the latest developments. The series will be posted tomorrow after
some more tests. However, there is one thing I wondered about:

> From now on, SER_RS485_RTS_AFTER_SEND and SER_RS485_RTS_ON_SEND will be used to
> set the voltage of the RTS pin (as in the crisv10.c driver); the delay will be
> understood by looking only at the value of delay_rts_before_send and 
> delay_rts_after_send.

Do I overlook something or is SER_RS485_RTS_AFTER_SEND always the inverted
signal of SER_RS485_RTS_ON_SEND. So why do we need both? (BTW
SER_RS485_RTS_ON_SEND is a non-obvious name, I think. But changing it will
probably break even more users?)

> diff --git a/include/linux/serial.h b/include/linux/serial.h
> index 97ff8e2..3d86517 100644
> --- a/include/linux/serial.h
> +++ b/include/linux/serial.h
> @@ -207,13 +207,15 @@ struct serial_icounter_struct {
>  
>  struct serial_rs485 {
>  	__u32	flags;			/* RS485 feature flags */
> -#define SER_RS485_ENABLED		(1 << 0)
> -#define SER_RS485_RTS_ON_SEND		(1 << 1)
> -#define SER_RS485_RTS_AFTER_SEND	(1 << 2)
> -#define SER_RS485_RTS_BEFORE_SEND	(1 << 3)
> +#define SER_RS485_ENABLED		(1 << 0)	/* If enabled */
> +#define SER_RS485_RTS_ON_SEND		(1 << 1)	/* Logical level for
> +							   RTS pin when
> +							   sending */
> +#define SER_RS485_RTS_AFTER_SEND	(1 << 2)	/* Logical level for
> +							   RTS pin after sent*/

Nit: 80 char should be broken here, because that is not readable. Or put the
comment above the define.

Thanks,

   Wolfram

-- 
Pengutronix e.K.                           | Wolfram Sang                |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

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