linux-kernel - Re: [PATCH 1/8] serial: core: only get RS485 termination gpio if supported

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Date:   Sat, 2 Jul 2022 18:50:59 +0200
From:   Lino Sanfilippo <LinoSanfilippo@....de>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        Lukas Wunner <lukas@...ner.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>, p.rosenberger@...bus.com,
        Lino Sanfilippo <l.sanfilippo@...bus.com>
Subject: Re: [PATCH 1/8] serial: core: only get RS485 termination gpio if
 supported

Hi,

On 27.06.22 11:05, Ilpo Järvinen wrote:
> On Sat, 25 Jun 2022, Lukas Wunner wrote:

>>
>> I think what you want to do is amend uart_get_rs485_mode() to set
>> SER_RS485_TERMINATE_BUS in port->rs485_supported_flags if a GPIO
>> was found in the DT.  Instead of the change proposed above.

Agreed.

>
> That seems appropriate (and is a fix).
>
> What makes it a bit complicated though is that it's a pointer currently
> and what it points to is shared per driver (besides being const):
> 	const struct serial_rs485       *rs485_supported;
> While it could be embedded into uart_port, there's the .padding which we
> might not want to bloat uart_port with. Perhaps create non-uapi struct
> kserial_rs485 w/o .padding and add static_assert()s to ensure the
> layout is identical to serial_rs485?
>
>

This seems to be indeed the cleanest solution.

Regards,
Lino