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From:   Lino Sanfilippo <LinoSanfilippo@gmx.de>
Subject: Re: [PATCH 1/8] serial: core: only get RS485 termination gpio if
 supported
To:     Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc:     gregkh@linuxfoundation.org, jirislaby@kernel.org,
        ilpo.jarvinen@linux.intel.com, robh+dt@kernel.org,
        krzysztof.kozlowski+dt@linaro.org, vz@mleia.com,
        linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org,
        linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
        lukas@wunner.de, p.rosenberger@kunbus.com,
        Lino Sanfilippo <l.sanfilippo@kunbus.com>
References: <20220622154659.8710-1-LinoSanfilippo@gmx.de>
 <20220622154659.8710-2-LinoSanfilippo@gmx.de>
 <YrNLtg+BZlwKsBbF@smile.fi.intel.com>
Message-ID: <2dda5707-6f13-6d33-863d-a88b89e88a88@gmx.de>
Date:   Thu, 23 Jun 2022 03:59:25 +0200
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Hi,

On 22.06.22 at 19:04, Andy Shevchenko wrote:
> On Wed, Jun 22, 2022 at 05:46:52PM +0200, Lino Sanfilippo wrote:
>> From: Lino Sanfilippo <l.sanfilippo@kunbus.com>
>>
>> In uart_get_rs485_mode() only try to get a termination GPIO if RS485 bu=
s
>> termination is supported by the driver.
>
> I'm not sure I got the usefulness of this change.
> We request GPIO line as optional, so if one is defined it in the DT/ACPI=
, then
> they probably want to (opportunistically) have it>
>
> With your change it's possible to have a DTS where GPIO line defined in =
a
> broken way and user won't ever know about it, if they are using platform=
s
> without termination support.
>

This behavior is not introduced with this patch, also in the current code =
the driver
wont inform the user if it does not make use erroneous defined termination=
 GPIO.

This patch at least prevents the driver from allocating and holding a GPIO=
 descriptor across
the drivers lifetime that will never be used.

Furthermore it simplifies the code in patch 2 when we want to set the GPIO=
, since we can
skip the check whether or not the termination GPIO is supported by the dri=
ver.


Regards,
Lino