[PATCH 00/10] drivers/pci: avoid module_init in non-modular host/pci*

[PATCH 00/10] drivers/pci: avoid module_init in non-modular host/pci*

[Paul Gortmaker]

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.

I have more "avoid module usage in non-modular code" cleanups for the
PCI subsystem, but these all have a common theme and it makes for a
more maintainer friendly series size to just ask to digest these 1st.

Testing was done on linux-next, using an ARCH=arm allmodconfig and then
explicitly building the files changed in this series.  If desired, I
can provide a v4.4-rc4 based branch for merging vs e-mail processing,
since I don't think the underlying baseline is overly important for
this (largely trivial) series of patches.

Paul.
---

Cc: Alexandre Courbot <gnurou@gmail.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Kishon Vijay Abraham I <kishon@ti.com>
Cc: Ley Foon Tan <lftan@altera.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: Murali Karicheri <m-karicheri2@ti.com>
Cc: Pratyush Anand <pratyush.anand@gmail.com>
Cc: Richard Zhu <Richard.Zhu@freescale.com>
Cc: Simon Horman <horms@verge.net.au>
Cc: "S?ren Brinkmann" <soren.brinkmann@xilinx.com>
Cc: Stephen Warren <swarren@wwwdotorg.org>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

Cc: linux-arm-kernel at lists.infradead.org
Cc: linux-omap at vger.kernel.org
Cc: linux-pci at vger.kernel.org
Cc: linux-sh at vger.kernel.org
Cc: linux-tegra at vger.kernel.org
Cc: rfi at lists.rocketboards.org

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

 drivers/pci/host/pci-dra7xx.c     | 31 +++--------------------
 drivers/pci/host/pci-imx6.c       | 12 +++------
 drivers/pci/host/pci-keystone.c   | 21 +++-------------
 drivers/pci/host/pci-mvebu.c      | 11 +++-----
 drivers/pci/host/pci-rcar-gen2.c  | 12 +++------
 drivers/pci/host/pci-tegra.c      | 11 +++-----
 drivers/pci/host/pcie-altera.c    | 12 ++++-----
 drivers/pci/host/pcie-rcar.c      | 11 +++-----
 drivers/pci/host/pcie-spear13xx.c | 10 +++-----
 drivers/pci/host/pcie-xilinx.c    | 53 ++-------------------------------------
 10 files changed, 35 insertions(+), 149 deletions(-)

-- 
2.6.1

[PATCH 01/10] drivers/pci: make host/pci-imx6.c driver explicitly non-modular

[Paul Gortmaker]

The Kconfig for this option is currently:

config PCI_IMX6
        bool "Freescale i.MX6 PCIe controller"

...meaning that it currently is not being built as a module by anyone.
Lets remove the couple traces of modularity, so that when reading the
driver there is no doubt it is builtin-only.

Since module_init translates to device_initcall in the non-modular
case, the init ordering remains unchanged with this commit.  An
alternate init level might be worth considering at a later date.

We explicitly disallow a driver unbind, since that doesn't have a
sensible use case anyway, and there wasn't a supplied ".remove"
function to be called either.

We also delete the MODULE_LICENSE tag etc. since all that information
is already contained at the top of the file in the comments.

Also note that MODULE_DEVICE_TABLE is a no-op for non-modular code.

Cc: Richard Zhu <Richard.Zhu@freescale.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-pci at vger.kernel.org
Cc: linux-arm-kernel at lists.infradead.org
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
 drivers/pci/host/pci-imx6.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
index 22e8224126fd..ddd6a752b554 100644
--- a/drivers/pci/host/pci-imx6.c
+++ b/drivers/pci/host/pci-imx6.c
@@ -17,7 +17,7 @@
 #include <linux/kernel.h>
 #include <linux/mfd/syscon.h>
 #include <linux/mfd/syscon/imx6q-iomuxc-gpr.h>
-#include <linux/module.h>
+#include <linux/init.h>
 #include <linux/of_gpio.h>
 #include <linux/pci.h>
 #include <linux/platform_device.h>
@@ -641,24 +641,20 @@ static const struct of_device_id imx6_pcie_of_match[] = {
 	{ .compatible = "fsl,imx6q-pcie", },
 	{},
 };
-MODULE_DEVICE_TABLE(of, imx6_pcie_of_match);
 
 static struct platform_driver imx6_pcie_driver = {
 	.driver = {
 		.name	= "imx6q-pcie",
 		.of_match_table = imx6_pcie_of_match,
+		.suppress_bind_attrs = true,
 	},
 	.shutdown = imx6_pcie_shutdown,
 };
 
-/* Freescale PCIe driver does not allow module unload */
+/* Freescale PCIe driver does not support module configuration */
 
 static int __init imx6_pcie_init(void)
 {
 	return platform_driver_probe(&imx6_pcie_driver, imx6_pcie_probe);
 }
-module_init(imx6_pcie_init);
-
-MODULE_AUTHOR("Sean Cross <xobs@kosagi.com>");
-MODULE_DESCRIPTION("Freescale i.MX6 PCIe host controller driver");
-MODULE_LICENSE("GPL v2");
+device_initcall(imx6_pcie_init);
-- 
2.6.1

[PATCH 01/10] drivers/pci: make host/pci-imx6.c driver explicitly non-modular

[Arnd Bergmann]

On Saturday 12 December 2015 20:41:48 Paul Gortmaker wrote:
> The Kconfig for this option is currently:
> 
> config PCI_IMX6
>         bool "Freescale i.MX6 PCIe controller"
> 
> ...meaning that it currently is not being built as a module by anyone.
> Lets remove the couple traces of modularity, so that when reading the
> driver there is no doubt it is builtin-only.

Can you fix Kconfig instead?

	Arnd

[PATCH 03/10] drivers/pci: make host/pci-mvebu.c explicitly non-modular

[Paul Gortmaker]

The Kconfig currently controlling compilation of this code is:

drivers/pci/host/Kconfig:config PCI_MVEBU
drivers/pci/host/Kconfig:       bool "Marvell EBU PCIe controller"

...meaning that it currently is not being built as a module by anyone.

Lets remove the modular code that is essentially orphaned, so that
when reading the driver there is no doubt it is builtin-only.

Since module_platform_driver() uses the same init level priority as
builtin_platform_driver() the init ordering remains unchanged with
this commit.

We don't have to disallow a driver unbind, since that is already
done for us in this driver.

Also note that MODULE_DEVICE_TABLE is a no-op for non-modular code.

We also delete the MODULE_LICENSE tag etc. since all that information
was (or is now ) contained at the top of the file in the comments.

Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-pci at vger.kernel.org
Cc: linux-arm-kernel at lists.infradead.org
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
 drivers/pci/host/pci-mvebu.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/drivers/pci/host/pci-mvebu.c b/drivers/pci/host/pci-mvebu.c
index 53b79c5f0559..17222f1a3ef3 100644
--- a/drivers/pci/host/pci-mvebu.c
+++ b/drivers/pci/host/pci-mvebu.c
@@ -1,6 +1,8 @@
 /*
  * PCIe driver for Marvell Armada 370 and Armada XP SoCs
  *
+ * Module Author: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
+ *
  * This file is licensed under the terms of the GNU General Public
  * License version 2.  This program is licensed "as is" without any
  * warranty of any kind, whether express or implied.
@@ -11,7 +13,7 @@
 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/gpio.h>
-#include <linux/module.h>
+#include <linux/init.h>
 #include <linux/mbus.h>
 #include <linux/msi.h>
 #include <linux/slab.h>
@@ -1296,7 +1298,6 @@ static const struct of_device_id mvebu_pcie_of_match_table[] = {
 	{ .compatible = "marvell,kirkwood-pcie", },
 	{},
 };
-MODULE_DEVICE_TABLE(of, mvebu_pcie_of_match_table);
 
 static struct dev_pm_ops mvebu_pcie_pm_ops = {
 	.suspend_noirq = mvebu_pcie_suspend,
@@ -1313,8 +1314,4 @@ static struct platform_driver mvebu_pcie_driver = {
 	},
 	.probe = mvebu_pcie_probe,
 };
-module_platform_driver(mvebu_pcie_driver);
-
-MODULE_AUTHOR("Thomas Petazzoni <thomas.petazzoni@free-electrons.com>");
-MODULE_DESCRIPTION("Marvell EBU PCIe driver");
-MODULE_LICENSE("GPL v2");
+builtin_platform_driver(mvebu_pcie_driver);
-- 
2.6.1

[PATCH 03/10] drivers/pci: make host/pci-mvebu.c explicitly non-modular

[Thomas Petazzoni]

Paul,

On Sat, 12 Dec 2015 20:41:50 -0500, Paul Gortmaker wrote:
> The Kconfig currently controlling compilation of this code is:
> 
> drivers/pci/host/Kconfig:config PCI_MVEBU
> drivers/pci/host/Kconfig:       bool "Marvell EBU PCIe controller"
> 
> ...meaning that it currently is not being built as a module by anyone.
> 
> Lets remove the modular code that is essentially orphaned, so that
> when reading the driver there is no doubt it is builtin-only.
> 
> Since module_platform_driver() uses the same init level priority as
> builtin_platform_driver() the init ordering remains unchanged with
> this commit.
> 
> We don't have to disallow a driver unbind, since that is already
> done for us in this driver.
> 
> Also note that MODULE_DEVICE_TABLE is a no-op for non-modular code.
> 
> We also delete the MODULE_LICENSE tag etc. since all that information
> was (or is now ) contained at the top of the file in the comments.
> 
> Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
> Cc: Jason Cooper <jason@lakedaemon.net>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: linux-pci at vger.kernel.org
> Cc: linux-arm-kernel at lists.infradead.org
> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
> ---
>  drivers/pci/host/pci-mvebu.c | 11 ++++-------
>  1 file changed, 4 insertions(+), 7 deletions(-)

I think the general direction should rather be to change the PCI
subsystem to make it possible for those drivers to be built as modules.
However, since this is quite certainly a much larger effort, there is
no reason to not clean things up as they are today, so:

Reviewed-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

Thanks,

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

[PATCH 03/10] drivers/pci: make host/pci-mvebu.c explicitly non-modular

[Arnd Bergmann]

On Saturday 12 December 2015 20:41:50 Paul Gortmaker wrote:
> The Kconfig currently controlling compilation of this code is:
> 
> drivers/pci/host/Kconfig:config PCI_MVEBU
> drivers/pci/host/Kconfig:       bool "Marvell EBU PCIe controller"
> 
> ...meaning that it currently is not being built as a module by anyone.

Here too. I think we should really try to let all PCI host drivers be
loadable modules if possible. The module unload path is currently
a bit iffy because of the way it interacts with the arch/arm PCI
infrastructure, but we are in the process of fixing it.

For now, I think allowing all PCIe host drivers for ARM to be
loadable but non-removably modules would be ideal.

	Arnd

[PATCH 08/10] drivers/pci: make host/pcie-xilinx.c explicitly non-modular

[Paul Gortmaker]

The Kconfig currently controlling compilation of this code is:

drivers/pci/host/Kconfig:config PCIE_XILINX
drivers/pci/host/Kconfig:       bool "Xilinx AXI PCIe host bridge support"

...meaning that it currently is not being built as a module by anyone.

Lets remove the modular code that is essentially orphaned, so that
when reading the driver there is no doubt it is builtin-only.  This
makes xilinx_pcie_free_irq_domain orphaned so we remove it too.

We don't have to worry about disallowing a driver unbind, since this
driver already does that.

Since module_platform_driver() uses the same init level priority as
builtin_platform_driver() the init ordering remains unchanged with
this commit.

We also delete the MODULE_LICENSE tag etc. since all that information
is already contained at the top of the file in the comments.

Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: "S?ren Brinkmann" <soren.brinkmann@xilinx.com>
Cc: linux-pci at vger.kernel.org
Cc: linux-arm-kernel at lists.infradead.org
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
 drivers/pci/host/pcie-xilinx.c | 53 ++----------------------------------------
 1 file changed, 2 insertions(+), 51 deletions(-)

diff --git a/drivers/pci/host/pcie-xilinx.c b/drivers/pci/host/pcie-xilinx.c
index 3c7a0d580b1e..73b5e856f9c2 100644
--- a/drivers/pci/host/pcie-xilinx.c
+++ b/drivers/pci/host/pcie-xilinx.c
@@ -18,7 +18,7 @@
 #include <linux/irq.h>
 #include <linux/irqdomain.h>
 #include <linux/kernel.h>
-#include <linux/module.h>
+#include <linux/init.h>
 #include <linux/msi.h>
 #include <linux/of_address.h>
 #include <linux/of_pci.h>
@@ -516,35 +516,6 @@ static irqreturn_t xilinx_pcie_intr_handler(int irq, void *data)
 }
 
 /**
- * xilinx_pcie_free_irq_domain - Free IRQ domain
- * @port: PCIe port information
- */
-static void xilinx_pcie_free_irq_domain(struct xilinx_pcie_port *port)
-{
-	int i;
-	u32 irq, num_irqs;
-
-	/* Free IRQ Domain */
-	if (IS_ENABLED(CONFIG_PCI_MSI)) {
-
-		free_pages(port->msi_pages, 0);
-
-		num_irqs = XILINX_NUM_MSI_IRQS;
-	} else {
-		/* INTx */
-		num_irqs = 4;
-	}
-
-	for (i = 0; i < num_irqs; i++) {
-		irq = irq_find_mapping(port->irq_domain, i);
-		if (irq > 0)
-			irq_dispose_mapping(irq);
-	}
-
-	irq_domain_remove(port->irq_domain);
-}
-
-/**
  * xilinx_pcie_init_irq_domain - Initialize IRQ domain
  * @port: PCIe port information
  *
@@ -858,21 +829,6 @@ static int xilinx_pcie_probe(struct platform_device *pdev)
 	return 0;
 }
 
-/**
- * xilinx_pcie_remove - Remove function
- * @pdev: Platform device pointer
- *
- * Return: '0' always
- */
-static int xilinx_pcie_remove(struct platform_device *pdev)
-{
-	struct xilinx_pcie_port *port = platform_get_drvdata(pdev);
-
-	xilinx_pcie_free_irq_domain(port);
-
-	return 0;
-}
-
 static struct of_device_id xilinx_pcie_of_match[] = {
 	{ .compatible = "xlnx,axi-pcie-host-1.00.a", },
 	{}
@@ -885,10 +841,5 @@ static struct platform_driver xilinx_pcie_driver = {
 		.suppress_bind_attrs = true,
 	},
 	.probe = xilinx_pcie_probe,
-	.remove = xilinx_pcie_remove,
 };
-module_platform_driver(xilinx_pcie_driver);
-
-MODULE_AUTHOR("Xilinx Inc");
-MODULE_DESCRIPTION("Xilinx AXI PCIe driver");
-MODULE_LICENSE("GPL v2");
+builtin_platform_driver(xilinx_pcie_driver);
-- 
2.6.1

[PATCH 08/10] drivers/pci: make host/pcie-xilinx.c explicitly non-modular

[Michal Simek]

On 13.12.2015 02:41, Paul Gortmaker wrote:
> The Kconfig currently controlling compilation of this code is:
> 
> drivers/pci/host/Kconfig:config PCIE_XILINX
> drivers/pci/host/Kconfig:       bool "Xilinx AXI PCIe host bridge support"
> 
> ...meaning that it currently is not being built as a module by anyone.
> 
> Lets remove the modular code that is essentially orphaned, so that
> when reading the driver there is no doubt it is builtin-only.  This
> makes xilinx_pcie_free_irq_domain orphaned so we remove it too.

Right.

Acked-by: Michal Simek <michal.simek@xilinx.com>

Thanks,
Michal

[PATCH 09/10] drivers/pci: make host/pci-keystone.c explicitly non-modular

[Paul Gortmaker]

The Kconfig currently controlling compilation of this code is:

drivers/pci/host/Kconfig:config PCI_KEYSTONE
drivers/pci/host/Kconfig:       bool "TI Keystone PCIe controller"

...meaning that it currently is not being built as a module by anyone.

Lets remove the modular code that is essentially orphaned, so that
when reading the driver there is no doubt it is builtin-only.

We explicitly disallow a driver unbind, since that doesn't have a
sensible use case anyway, and it allows us to drop the ".remove"
code for non-modular drivers.

Since module_platform_driver() uses the same init level priority as
builtin_platform_driver() the init ordering remains unchanged with
this commit.

Also note that MODULE_DEVICE_TABLE is a no-op for non-modular code.

We also delete the MODULE_LICENSE tag etc. since all that information
is already contained at the top of the file in the comments.

Cc: Murali Karicheri <m-karicheri2@ti.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-pci at vger.kernel.org
Cc: linux-arm-kernel at lists.infradead.org
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
 drivers/pci/host/pci-keystone.c | 21 +++------------------
 1 file changed, 3 insertions(+), 18 deletions(-)

diff --git a/drivers/pci/host/pci-keystone.c b/drivers/pci/host/pci-keystone.c
index 0aa81bd3de12..0493d4257bde 100644
--- a/drivers/pci/host/pci-keystone.c
+++ b/drivers/pci/host/pci-keystone.c
@@ -16,7 +16,7 @@
 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/irqdomain.h>
-#include <linux/module.h>
+#include <linux/init.h>
 #include <linux/msi.h>
 #include <linux/of_irq.h>
 #include <linux/of.h>
@@ -329,16 +329,6 @@ static const struct of_device_id ks_pcie_of_match[] = {
 	},
 	{ },
 };
-MODULE_DEVICE_TABLE(of, ks_pcie_of_match);
-
-static int __exit ks_pcie_remove(struct platform_device *pdev)
-{
-	struct keystone_pcie *ks_pcie = platform_get_drvdata(pdev);
-
-	clk_disable_unprepare(ks_pcie->clk);
-
-	return 0;
-}
 
 static int __init ks_pcie_probe(struct platform_device *pdev)
 {
@@ -398,15 +388,10 @@ fail_clk:
 
 static struct platform_driver ks_pcie_driver __refdata = {
 	.probe  = ks_pcie_probe,
-	.remove = __exit_p(ks_pcie_remove),
 	.driver = {
 		.name	= "keystone-pcie",
 		.of_match_table = of_match_ptr(ks_pcie_of_match),
+		.suppress_bind_attrs = true,
 	},
 };
-
-module_platform_driver(ks_pcie_driver);
-
-MODULE_AUTHOR("Murali Karicheri <m-karicheri2@ti.com>");
-MODULE_DESCRIPTION("Keystone PCIe host controller driver");
-MODULE_LICENSE("GPL v2");
+builtin_platform_driver(ks_pcie_driver);
-- 
2.6.1

[PATCH 00/10] drivers/pci: avoid module_init in non-modular host/pci*

[Geert Uytterhoeven]

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.

> 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 at linux-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

[PATCH 00/10] drivers/pci: avoid module_init in non-modular host/pci*

[Thierry Reding]

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.

Thierry
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 819 bytes
Desc: not available
URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20151214/21036b5d/attachment.sig>

[PATCH 00/10] drivers/pci: avoid module_init in non-modular host/pci*

[Michal Simek]

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

[PATCH 00/10] drivers/pci: avoid module_init in non-modular host/pci*

[Ley Foon Tan]

On Mon, Dec 14, 2015 at 4:24 PM, Thierry Reding
<thierry.reding@gmail.com> 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.
>
PCIe host driver that use fixup (DECLARE_PCI_FIXUP_*) can't use tristate.
Fixup region is in kernel region and this region if not updated when
loading a module.

Regards
Ley Foon

[PATCH 00/10] drivers/pci: avoid module_init in non-modular host/pci*

[Thierry Reding]

On Mon, Dec 14, 2015 at 04:33:51PM +0800, Ley Foon Tan wrote:
> On Mon, Dec 14, 2015 at 4:24 PM, Thierry Reding
> <thierry.reding@gmail.com> 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.
> >
> PCIe host driver that use fixup (DECLARE_PCI_FIXUP_*) can't use tristate.
> Fixup region is in kernel region and this region if not updated when
> loading a module.

Interesting, I hadn't thought about that. I suppose this means that the
module will end up containing an unused section with the fixup code. It
might be useful to add a way for that to trigger a warning at build
time.

Perhaps to fix this a mechanism could be introduced to add a table of
fixups to a host controller driver and that will get applied to all
children of the bridge. It could be problematic to cover all of the
different fixup stages, though.

Thierry
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 819 bytes
Desc: not available
URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20151214/46147b8a/attachment-0001.sig>

[PATCH 00/10] drivers/pci: avoid module_init in non-modular host/pci*

[Arnd Bergmann]

On Monday 14 December 2015 10:19:40 Thierry Reding wrote:
> > PCIe host driver that use fixup (DECLARE_PCI_FIXUP_*) can't use tristate.
> > Fixup region is in kernel region and this region if not updated when
> > loading a module.
> 
> Interesting, I hadn't thought about that. I suppose this means that the
> module will end up containing an unused section with the fixup code. It
> might be useful to add a way for that to trigger a warning at build
> time.
> 
> Perhaps to fix this a mechanism could be introduced to add a table of
> fixups to a host controller driver and that will get applied to all
> children of the bridge. It could be problematic to cover all of the
> different fixup stages, though.
> 


I think a lot of the fixups shouldn't really be there in the first place,
they are about stuff that we can fix up in the probe function, or that should
be fixed up in the probe function with some appropriate core support added.

	Arnd

[PATCH 00/10] drivers/pci: avoid module_init in non-modular host/pci*

[Paul Gortmaker]

[Re: [PATCH 00/10] drivers/pci: avoid module_init in non-modular host/pci*] On 14/12/2015 (Mon 11:27) Arnd Bergmann wrote:

> On Monday 14 December 2015 10:19:40 Thierry Reding wrote:
> > > PCIe host driver that use fixup (DECLARE_PCI_FIXUP_*) can't use tristate.
> > > Fixup region is in kernel region and this region if not updated when
> > > loading a module.
> > 
> > Interesting, I hadn't thought about that. I suppose this means that the
> > module will end up containing an unused section with the fixup code. It
> > might be useful to add a way for that to trigger a warning at build
> > time.
> > 
> > Perhaps to fix this a mechanism could be introduced to add a table of
> > fixups to a host controller driver and that will get applied to all
> > children of the bridge. It could be problematic to cover all of the
> > different fixup stages, though.
> > 
> 
> 
> I think a lot of the fixups shouldn't really be there in the first place,
> they are about stuff that we can fix up in the probe function, or that should
> be fixed up in the probe function with some appropriate core support added.

So, the feedback on this is a bit all over the map, leaving me unsure
what to do next.  And is the choice we make on a per board/bsp basis or
ideally across all platforms?  I see the choices as:

1) do nothing; which IMHO is least desirable as it leaves the code
misrepresenting itself as modular; one of the key issues I wanted to fix

2) use the patches I've sent ; then as they are genuinely made modular,
the person doing so essentially "patch -R" or reverts the change as
step one.  This has the advantage of solving the "we'll get to it
someday" issue if someday never comes.

3) make them all tristate;  beat it with a stick until it compiles [M]
and modposts -- leaving the fixups and functional testing to people with
the boards and low level knowledge to make it _work_ as a module.  The
downside here is the code is still kind of misrepresenting itself as
modularly functional -- a ban of unloading might mitigate that some.

Paul.
--

> 
> 	Arnd

[PATCH 00/10] drivers/pci: avoid module_init in non-modular host/pci*

[Bjorn Helgaas]

On Tue, Dec 15, 2015 at 10:16:24AM -0500, Paul Gortmaker wrote:
> [Re: [PATCH 00/10] drivers/pci: avoid module_init in non-modular host/pci*] On 14/12/2015 (Mon 11:27) Arnd Bergmann wrote:
> 
> > On Monday 14 December 2015 10:19:40 Thierry Reding wrote:
> > > > PCIe host driver that use fixup (DECLARE_PCI_FIXUP_*) can't use tristate.
> > > > Fixup region is in kernel region and this region if not updated when
> > > > loading a module.
> > > 
> > > Interesting, I hadn't thought about that. I suppose this means that the
> > > module will end up containing an unused section with the fixup code. It
> > > might be useful to add a way for that to trigger a warning at build
> > > time.
> > > 
> > > Perhaps to fix this a mechanism could be introduced to add a table of
> > > fixups to a host controller driver and that will get applied to all
> > > children of the bridge. It could be problematic to cover all of the
> > > different fixup stages, though.
> > 
> > I think a lot of the fixups shouldn't really be there in the first place,
> > they are about stuff that we can fix up in the probe function, or that should
> > be fixed up in the probe function with some appropriate core support added.
> 
> So, the feedback on this is a bit all over the map, leaving me unsure
> what to do next.  And is the choice we make on a per board/bsp basis or
> ideally across all platforms?  I see the choices as:
> 
> 1) do nothing; which IMHO is least desirable as it leaves the code
> misrepresenting itself as modular; one of the key issues I wanted to fix
> 
> 2) use the patches I've sent ; then as they are genuinely made modular,
> the person doing so essentially "patch -R" or reverts the change as
> step one.  This has the advantage of solving the "we'll get to it
> someday" issue if someday never comes.
> 
> 3) make them all tristate;  beat it with a stick until it compiles [M]
> and modposts -- leaving the fixups and functional testing to people with
> the boards and low level knowledge to make it _work_ as a module.  The
> downside here is the code is still kind of misrepresenting itself as
> modularly functional -- a ban of unloading might mitigate that some.

I'd like to preserve the mind-set that host controller drivers are
*expected* to be modular, even if we aren't there yet.  I guess that
means I'm in favor of option 3, at least for drivers that don't use
fixups.

Bjorn