Subject: Re: [PATCH 00/10] drivers/pci: avoid module_init in non-modular
 host/pci*
To: Thierry Reding <thierry.reding@gmail.com>,
        Geert Uytterhoeven <geert@linux-m68k.org>
References: <1449970917-12633-1-git-send-email-paul.gortmaker@windriver.com>
 <CAMuHMdXr=ErCO3R2LB+wBJh3JSiFkH5q3-FLSTOwdGT87fXz3A@mail.gmail.com>
 <20151214082425.GA3766@ulmo.nvidia.com>
CC: Paul Gortmaker <paul.gortmaker@windriver.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Linux-sh list <linux-sh@vger.kernel.org>,
        linux-pci <linux-pci@vger.kernel.org>,
        "Alexandre Courbot" <gnurou@gmail.com>,
        Pratyush Anand <pratyush.anand@gmail.com>,
        "Michal Simek" <michal.simek@xilinx.com>,
        Kishon Vijay Abraham I <kishon@ti.com>,
        Murali Karicheri <m-karicheri2@ti.com>,
        =?UTF-8?Q?S=c3=b6ren_Brinkmann?= <soren.brinkmann@xilinx.com>,
        Jason Cooper <jason@lakedaemon.net>,
        "Stephen Warren" <swarren@wwwdotorg.org>,
        Simon Horman <horms@verge.net.au>, <linux-tegra@vger.kernel.org>,
        "linux-omap@vger.kernel.org" <linux-omap@vger.kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
        Thomas Petazzoni <thomas.petazzoni@free-electrons.com>,
        Richard Zhu <Richard.Zhu@freescale.com>, <rfi@lists.rocketboards.org>,
        Ley Foon Tan <lftan@altera.com>, Bjorn Helgaas <bhelgaas@google.com>,
        Lucas Stach <l.stach@pengutronix.de>
From: Michal Simek <michal.simek@xilinx.com>
Message-ID: <566E7D4E.8010406@xilinx.com>
Date: Mon, 14 Dec 2015 09:26:54 +0100
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On 14.12.2015 09:24, Thierry Reding wrote:
> On Mon, Dec 14, 2015 at 09:19:30AM +0100, Geert Uytterhoeven wrote:
>> Hi Paul,
>>
>> On Sun, Dec 13, 2015 at 2:41 AM, Paul Gortmaker
>> <paul.gortmaker@windriver.com> wrote:
>>> This series of commits is a slice of a larger project to ensure
>>> people don't have dead code for module removal in non-modular
>>> drivers.  Overall there was roughly 5k lines of dead code in the
>>> kernel due to this.  So far we've fixed several areas, like tty,
>>> x86, net, etc. and we continue to work on other areas.
>>>
>>> There are several reasons to not use module_init for code that can
>>> never be built as a module, but the big ones are:
>>>
>>>  (1) it is easy to accidentally code up unused module_exit and remove code
>>>  (2) it can be misleading when reading the source, thinking it can be
>>>       modular when the Makefile and/or Kconfig prohibit it
>>>  (3) it requires the include of the module.h header file which in turn
>>>      includes nearly everything else.
>>>
>>> Here we convert some module_init() calls into device_initcall() and delete
>>> any module_exit and remove code that gets orphaned in the process, for
>>> an overall net code reduction, which is always welcome.
>>>
>>> The use of device_initcall ensures that the init function ordering
>>> remains unchanged, but one could argue that PCI host code might be more
>>> appropriate to be handled under subsys_initcall.  Fortunately we can
>>> revisit making this extra change at a later date if desired; it does
>>> not need to happen now, and we reduce the risk of introducing
>>> regressions at this point in time by separating the two changes.
>>>
>>> Over half of the drivers changed here already explicitly disallowed any
>>> unbind operations.  For the rest we make them the same, since there is
>>> not really any sensible use case to unbind any built-in bus support that
>>> I can think of.
>>
>> Personally, I think all of these should become tristate, so distro kernels
>> don't have to build in PCI(e) support for all SoCs. multi_v7_defconfig kernels
>> are becoming too big.
>>
>> That does not preclude making these modules un-unloadable, though.
> 
> Most of these can't be made tristate as-is, because they use symbols
> that aren't exported. Many of those symbols can easily be exported, so
> its just a matter of getting the respective patches merged. I disagree
> with making the modules non-unloadable, though. I have a local branch
> with changes necessary to unload the host controller driver and it
> works just fine.

Great.

Send them out.

Thanks,
Michal

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