linux-kernel - Re: [PATCH 8/8] serial: exar: Add support for IOT2040 device

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Message-ID: <1ee7fc16-5bba-7be6-57b3-c6efaf9a1c6f@siemens.com>
Date:   Thu, 18 May 2017 12:37:34 +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 8/8] serial: exar: Add support for IOT2040 device

On 2017-05-18 12:17, Andy Shevchenko wrote:
> On Thu, May 18, 2017 at 8:06 AM, Jan Kiszka <jan.kiszka@...mens.com> wrote:
>> On 2017-05-13 15:54, Andy Shevchenko wrote:
>>> On Sat, May 13, 2017 at 10:29 AM, 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.
>>>>
>>>
>>> Please, refactor that using properly formed DMI structrure and use its
>>> callback and driver data facilities/
>>
>> Could you point to a specific example? The callback of the dmi_system_id
>> structure is not designed to handle device initializations like this one
>> - not to speak of having those two different initialization points here.
> 
> Sure.
> 
> drivers/platform/x86/dell-laptop.c:
> 
> static const struct dmi_system_id dell_quirks[] __initconst = {
>         {
>                 .callback = dmi_matched,
>                 .ident = "Dell Vostro V130",
>                 .matches = {
>                         DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
>                         DMI_MATCH(DMI_PRODUCT_NAME, "Vostro V130"),
>                 },
>                 .driver_data = &quirk_dell_vostro_v130,
>         },
> 
> 
> (just in case, dmi_matched() is part of that module)
> 

OK, but that would basically replace the two lines for matching against
the DMI values with the structure above. We would still need the
existing hooks at the two points where we have them right now. Doesn't
look to me as if the code would become clearer or better separated or
easier extensible (the latter being hard anyway without knowing any
potential third special case).

Jan

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