linux-kernel - Re: [PATCH v2 1/9] serial: core: only get RS485 termination GPIO if supported

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Date:   Sun, 3 Jul 2022 20:27:39 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Lino Sanfilippo <LinoSanfilippo@....de>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Vladimir Zapolskiy <vz@...ia.com>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        devicetree <devicetree@...r.kernel.org>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Lukas Wunner <lukas@...ner.de>, p.rosenberger@...bus.com,
        Lino Sanfilippo <l.sanfilippo@...bus.com>
Subject: Re: [PATCH v2 1/9] serial: core: only get RS485 termination GPIO if supported

On Sun, Jul 3, 2022 at 7:02 PM Lino Sanfilippo <LinoSanfilippo@....de> wrote:
>
> From: Lino Sanfilippo <l.sanfilippo@...bus.com>
>
> In uart_get_rs485_mode() only try to get a termination GPIO if RS485 bus
> termination is supported by the driver. This prevents from allocating
> and holding a GPIO descriptor for the drivers lifetimg that will never be

lifetiming

> used.

...

>         port->rs485_term_gpio = devm_gpiod_get_optional(dev, "rs485-term",
>                                                         GPIOD_OUT_LOW);
> +
> +       if (port->rs485_term_gpio &&

This check is incorrect. Either you need to move that after error
checking (that's what I personally prefer), or use !IS_ERR_OR_NULL().

> +           !(port->rs485_supported->flags & SER_RS485_TERMINATE_BUS)) {
> +               dev_warn(port->dev,
> +                       "%s (%d): RS485 termination gpio not supported by driver\n",
> +                       port->name, port->line);
> +               devm_gpiod_put(dev, port->rs485_term_gpio);
> +               port->rs485_term_gpio = NULL;
> +       }
> +
>         if (IS_ERR(port->rs485_term_gpio)) {
>                 ret = PTR_ERR(port->rs485_term_gpio);
>                 port->rs485_term_gpio = NULL;


-- 
With Best Regards,
Andy Shevchenko