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From:   Lino Sanfilippo <LinoSanfilippo@gmx.de>
To:     Jiri Slaby <jirislaby@kernel.org>
Cc:     Greg KH <gregkh@linuxfoundation.org>, linux@armlinux.org.uk,
        linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] serial: amba-pl011: add RS485 support
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Date:   Fri, 25 Jun 2021 13:21:56 +0200
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References: <20210618145153.1906-1-LinoSanfilippo@gmx.de>
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Hi,

> On 25. 06. 21, 2:15, Lino Sanfilippo wrote:
> >>> +static int pl011_rs485_config(struct uart_port *port,
> >>> +			      struct serial_rs485 *rs485)
> >>> +{
> >>> +	struct uart_amba_port *uap =3D
> >>> +		container_of(port, struct uart_amba_port, port);
> >>> +
> >>> +	/* pick sane settings if the user hasn't */
> >>> +	if (!!(rs485->flags & SER_RS485_RTS_ON_SEND) =3D=3D
> >>
> >> Why the !! in an if statement?
> >>
> >>> +	    !!(rs485->flags & SER_RS485_RTS_AFTER_SEND)) {
> >>
> >> Same here, why?
> >>
> >
> > This was copied from serial8250_em485_config(). But I think we can sim=
ply use
> >
> > 	if (rs485->flags & SER_RS485_RTS_AFTER_SEND)
> > 		rs485->flags &=3D ~SER_RS485_RTS_ON_SEND;
> > 	else
> > 		rs485->flags |=3D SER_RS485_RTS_ON_SEND;
> >
> > instead. I will adjust the code accordingly.
>
> This is different. You want to set ON_SEND when none is set. And unset
> AFTER_SEND when both are set. In your code, when both are set, you leave
> AFTER_SEND.
>
> regards,
> --
> js
> suse labs
>

Thats right, the logic has slightly changed. I thought this does not matte=
r as long as
we make sure that exactly one of both ON_SEND or AFTER_SEND is set. We can=
 stick with the logic
in serial8250_em485_config() (i.e. always set ON_SEND and delete AFTER_SEN=
D in case
of an invalid setting), but I think this will require more than the four l=
ines that we
have now (especially if we want to avoid the !!).

Thanks,
Lino