linux-kernel - Re: [PATCH] PCI: dwc: layerscape: convert to builtin_platform

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Date:   Mon, 25 Jan 2021 20:49:32 +0100
From:   Michael Walle <michael@...le.cc>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Saravana Kannan <saravanak@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Roy Zang <roy.zang@....com>, PCI <linux-pci@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Minghuan Lian <minghuan.Lian@....com>,
        Mingkai Hu <mingkai.hu@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] PCI: dwc: layerscape: convert to
 builtin_platform_driver()

Am 2021-01-21 12:01, schrieb Geert Uytterhoeven:
> Hi Saravana,
> 
> On Thu, Jan 21, 2021 at 1:05 AM Saravana Kannan <saravanak@...gle.com> 
> wrote:
>> On Wed, Jan 20, 2021 at 3:53 PM Michael Walle <michael@...le.cc> 
>> wrote:
>> > Am 2021-01-20 20:47, schrieb Saravana Kannan:
>> > > On Wed, Jan 20, 2021 at 11:28 AM Michael Walle <michael@...le.cc>
>> > > wrote:
>> > >>
>> > >> [RESEND, fat-fingered the buttons of my mail client and converted
>> > >> all CCs to BCCs :(]
>> > >>
>> > >> Am 2021-01-20 20:02, schrieb Saravana Kannan:
>> > >> > On Wed, Jan 20, 2021 at 6:24 AM Rob Herring <robh@...nel.org> wrote:
>> > >> >>
>> > >> >> On Wed, Jan 20, 2021 at 4:53 AM Michael Walle <michael@...le.cc>
>> > >> >> wrote:
>> > >> >> >
>> > >> >> > fw_devlink will defer the probe until all suppliers are ready. We can't
>> > >> >> > use builtin_platform_driver_probe() because it doesn't retry after probe
>> > >> >> > deferral. Convert it to builtin_platform_driver().
>> > >> >>
>> > >> >> If builtin_platform_driver_probe() doesn't work with fw_devlink, then
>> > >> >> shouldn't it be fixed or removed?
>> > >> >
>> > >> > I was actually thinking about this too. The problem with fixing
>> > >> > builtin_platform_driver_probe() to behave like
>> > >> > builtin_platform_driver() is that these probe functions could be
>> > >> > marked with __init. But there are also only 20 instances of
>> > >> > builtin_platform_driver_probe() in the kernel:
>> > >> > $ git grep ^builtin_platform_driver_probe | wc -l
>> > >> > 20
>> > >> >
>> > >> > So it might be easier to just fix them to not use
>> > >> > builtin_platform_driver_probe().
>> > >> >
>> > >> > Michael,
>> > >> >
>> > >> > Any chance you'd be willing to help me by converting all these to
>> > >> > builtin_platform_driver() and delete builtin_platform_driver_probe()?
>> > >>
>> > >> If it just moving the probe function to the _driver struct and
>> > >> remove the __init annotations. I could look into that.
>> > >
>> > > Yup. That's pretty much it AFAICT.
>> > >
>> > > builtin_platform_driver_probe() also makes sure the driver doesn't ask
>> > > for async probe, etc. But I doubt anyone is actually setting async
>> > > flags and still using builtin_platform_driver_probe().
>> >
>> > Hasn't module_platform_driver_probe() the same problem? And there
>> > are ~80 drivers which uses that.
>> 
>> Yeah. The biggest problem with all of these is the __init markers.
>> Maybe some familiar with coccinelle can help?
> 
> And dropping them will increase memory usage.

Although I do have the changes for the builtin_platform_driver_probe()
ready, I don't think it makes much sense to send these unless we agree
on the increased memory footprint. While there are just a few
builtin_platform_driver_probe() and memory increase _might_ be
negligible, there are many more module_platform_driver_probe().

-michael