linux-kernel - Re: [PATCH 7/8] serial: ar933x: Remove redundant assignment in rs485

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Date:   Mon, 27 Jun 2022 11:14:34 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Lino Sanfilippo <LinoSanfilippo@....de>
cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        vz@...ia.com, linux-arm-kernel@...ts.infradead.org,
        devicetree@...r.kernel.org,
        linux-serial <linux-serial@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, lukas@...ner.de,
        p.rosenberger@...bus.com, Lino Sanfilippo <l.sanfilippo@...bus.com>
Subject: Re: [PATCH 7/8] serial: ar933x: Remove redundant assignment in
 rs485_config

On Sun, 26 Jun 2022, Lino Sanfilippo wrote:

> On 25.06.22 at 12:14, Ilpo Järvinen wrote:
> > On Wed, 22 Jun 2022, Lino Sanfilippo wrote:
> >
> >> From: Lino Sanfilippo <l.sanfilippo@...bus.com>
> >>
> >> In uart_set_rs485_config() the serial core already assigns the passed
> >> serial_rs485 struct to the uart port.
> >>
> >> So remove the assignment in the drivers rs485_config() function to avoid
> >> redundancy.
> >>
> >> Signed-off-by: Lino Sanfilippo <l.sanfilippo@...bus.com>
> >> ---
> >>  drivers/tty/serial/ar933x_uart.c | 1 -
> >>  1 file changed, 1 deletion(-)
> >>
> >> diff --git a/drivers/tty/serial/ar933x_uart.c b/drivers/tty/serial/ar933x_uart.c
> >> index ab2c5b2a1ce8..857e010d01dc 100644
> >> --- a/drivers/tty/serial/ar933x_uart.c
> >> +++ b/drivers/tty/serial/ar933x_uart.c
> >> @@ -591,7 +591,6 @@ static int ar933x_config_rs485(struct uart_port *port,
> >>  		dev_err(port->dev, "RS485 needs rts-gpio\n");
> >>  		return 1;
> >>  	}
> >> -	port->rs485 = *rs485conf;
> >>  	return 0;
> >>  }
> >
> > Hmm, I realize that for some reason I missed cleaning up this particular
> > driver after introducing the serial_rs485 sanitization. It shouldn't need
> > that preceeding if block either because ar933x_no_rs485 gets applied if
> > there's no rts_gpiod so the core clears SER_RS485_ENABLED.
> 
> I think we still need that "if" in case that RS485 was not enabled at driver
> startup (no rs485-enabled-at-boot-time) and no RTS GPIO was defined but then
> RS485 is enabled via TIOCSRS485.
> 
> Maybe in ar933x_uart_probe()
> 
> 	if ((port->rs485.flags & SER_RS485_ENABLED) &&
> 	    !up->rts_gpiod) {
> 		dev_err(&pdev->dev, "lacking rts-gpio, disabling RS485\n");
> 		port->rs485.flags &= ~SER_RS485_ENABLED;
> 		port->rs485_supported = &ar933x_no_rs485;
> 	}
> 
> should rather be

I think it would be better (and what I should have done while moving the 
check there in the first place but I missed it). In addition, however, it 
would be useful to not print unnecessarily:

> 	if (!up->rts_gpiod) {

if (port->rs485.flags & SER_RS485_ENABLED) {

> 		dev_err(&pdev->dev, "lacking rts-gpio, disabling RS485\n");
> 		port->rs485.flags &= ~SER_RS485_ENABLED;

}

> 		port->rs485_supported = &ar933x_no_rs485;
> 	}

-- 
 i.