linux-kernel - Re: [PATCH v5 30/44] rtc: add HAS

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Message-Id: <28a513fd-1e7c-4772-a3c1-f312938459ed@app.fastmail.com>
Date:   Tue, 04 Jul 2023 13:25:22 +0200
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Geert Uytterhoeven" <geert@...ux-m68k.org>,
        "Niklas Schnelle" <schnelle@...ux.ibm.com>
Cc:     "Alessandro Zummo" <a.zummo@...ertech.it>,
        "Alexandre Belloni" <alexandre.belloni@...tlin.com>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Bjorn Helgaas" <bhelgaas@...gle.com>,
        Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
        "Mauro Carvalho Chehab" <mchehab@...nel.org>,
        "Alan Stern" <stern@...land.harvard.edu>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        "Paul Walmsley" <paul.walmsley@...ive.com>,
        "Palmer Dabbelt" <palmer@...belt.com>,
        "Albert Ou" <aou@...s.berkeley.edu>, linux-kernel@...r.kernel.org,
        Linux-Arch <linux-arch@...r.kernel.org>,
        linux-pci@...r.kernel.org, "Arnd Bergmann" <arnd@...nel.org>,
        linux-rtc@...r.kernel.org, "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH v5 30/44] rtc: add HAS_IOPORT dependencies

On Tue, Jul 4, 2023, at 10:06, Geert Uytterhoeven wrote:
> Hi Niklas,
>
> On Mon, May 22, 2023 at 12:51 PM Niklas Schnelle <schnelle@...ux.ibm.com> wrote:
>> In a future patch HAS_IOPORT=n will result in inb()/outb() and friends
>> not being declared. We thus need to add HAS_IOPORT as dependency for
>> those drivers using them.
>>
>> Co-developed-by: Arnd Bergmann <arnd@...nel.org>
>> Signed-off-by: Arnd Bergmann <arnd@...nel.org>
>> Signed-off-by: Niklas Schnelle <schnelle@...ux.ibm.com>
>
> Thanks for your patch, which is now commit 8bb12adb214b2d7c ("rtc:
> add HAS_IOPORT dependencies") upstream.
>
>> --- a/drivers/rtc/Kconfig
>> +++ b/drivers/rtc/Kconfig
>> @@ -1193,7 +1195,7 @@ config RTC_DRV_MSM6242
>>
>>  config RTC_DRV_BQ4802
>>         tristate "TI BQ4802"
>> -       depends on HAS_IOMEM
>> +       depends on HAS_IOMEM && HAS_IOPORT
>>         help
>>           If you say Y here you will get support for the TI
>>           BQ4802 RTC chip.
>
> This driver can use either iomem or ioport.
> By adding a dependency on HAS_IOPORT, it can no longer be used
> on platforms that provide HAS_IOMEM only.

You are correct, we could allow building this driver even
without IOPORT and make it use ioport_map() or an #ifdef.

> Probably the driver should be refactored to make it use only
> the accessors that are available.

Since the driver itself has no DT support, it looks like the
only way it can be used is from the sparc64/ultra45 wrapper,
but that architecture always provides CONFIG_IOPORT, so I
don't think it makes any difference in the end. We can change
this again if another user comes up.

It might be good to know whether the machine uses a memory or
I/O resource in its device tree.

      Arnd