linux-kernel - Re: [PATCH v2 6/6] serial: exar: Add support for IOT2040 device

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Message-ID: <f3959f33-b82a-e64a-c04d-bfa7ab486402@siemens.com>
Date:   Thu, 18 May 2017 18:58:02 +0200
From:   Jan Kiszka <jan.kiszka@...mens.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Alexandre Courbot <gnurou@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        Sudip Mukherjee <sudip.mukherjee@...ethink.co.uk>,
        Sascha Weisenberger <sascha.weisenberger@...mens.com>
Subject: Re: [PATCH v2 6/6] serial: exar: Add support for IOT2040 device

On 2017-05-18 18:39, Jan Kiszka wrote:
> On 2017-05-18 18:33, Andy Shevchenko wrote:
>> On Thu, May 18, 2017 at 5:59 PM, Jan Kiszka <jan.kiszka@...mens.com> wrote:
>>> This implements the setup of RS232 and the switch-over to RS485 or RS422
>>> for the Siemens IOT2040. That uses an EXAR XR17V352 with external logic
>>> to switch between the different modes. The external logic is controlled
>>> via MPIO pins of the EXAR controller.
>>>
>>> Only pin 10 can be exported as GPIO on the IOT2040. It is connected to
>>> an LED.
>>>
>>> As the XR17V352 used on the IOT2040 is not equipped with an external
>>> EEPROM, it cannot present itself as IOT2040-variant via subvendor/
>>> subdevice IDs. Thus, we have to check via DMI for the target platform.
>>>
>>> Co-developed with Sascha Weisenberger.
>>
>> Few nits below and one comment that should be addressed.
>>
>>> +#define UART_EXAR_RS485_DLY(x) (x << 4)
>>
>> ((x) << 4)
> 
> Yep.
> 
>>
>>> +static bool is_iot2040;
>>
>> No, please, use driver data of DMI and hide this in corresponding structure.
>> Or even assign  port->port.rs485_config in the callback function.
>>
>> Moreover, can't you use port->port.rs485_config != NULL instead?
> 
> There are two cases to be handled on IOT2040: the setting of the
> rs485_config and the different setup of the GPIOs, but the latter at a
> specific point in the initialization only. So I don't see yet how
> driver_data could come into play and help.
> 

OK, got - hacking...

Jan

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