linux-kernel - Re: [PATCH 00/10] drivers/pci: avoid module

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Date:	Mon, 14 Dec 2015 09:19:30 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Paul Gortmaker <paul.gortmaker@...driver.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux-sh list <linux-sh@...r.kernel.org>,
	linux-pci <linux-pci@...r.kernel.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Alexandre Courbot <gnurou@...il.com>,
	Pratyush Anand <pratyush.anand@...il.com>,
	Michal Simek <michal.simek@...inx.com>,
	Kishon Vijay Abraham I <kishon@...com>,
	Murali Karicheri <m-karicheri2@...com>,
	Sören Brinkmann <soren.brinkmann@...inx.com>,
	Jason Cooper <jason@...edaemon.net>,
	Stephen Warren <swarren@...dotorg.org>,
	Simon Horman <horms@...ge.net.au>, linux-tegra@...r.kernel.org,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Richard Zhu <Richard.Zhu@...escale.com>,
	rfi@...ts.rocketboards.org, Ley Foon Tan <lftan@...era.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Lucas Stach <l.stach@...gutronix.de>
Subject: Re: [PATCH 00/10] drivers/pci: avoid module_init in non-modular host/pci*

Hi Paul,

On Sun, Dec 13, 2015 at 2:41 AM, Paul Gortmaker
<paul.gortmaker@...driver.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.

> Paul Gortmaker (10):
>   drivers/pci: make host/pci-imx6.c driver explicitly non-modular
>   drivers/pci: make host/pcie-spear13xx.c driver explicitly non-modular
>   drivers/pci: make host/pci-mvebu.c explicitly non-modular
>   drivers/pci: make host/pci-dra7xx.c explicitly non-modular
>   drivers/pci: make host/pci-rcar-gen2.c explicitly non-modular
>   drivers/pci: make host/pci-tegra.c explicitly non-modular
>   drivers/pci: make host/pcie-rcar.c explicitly non-modular
>   drivers/pci: make host/pcie-xilinx.c explicitly non-modular
>   drivers/pci: make host/pci-keystone.c explicitly non-modular
>   drivers/pci: make host/pcie-altera.c explicitly non-modular

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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