[PATCH 0/5] drivers/tty: make more bool drivers explicitly non-modular

This next set of patches to drivers/tty fixes up more drivers that would
perhaps appear modular when looking at the code, but are controlled by
a bool Kconfig.  We make sure they don't look modular and get rid
of module related code in the drivers that would never be used.

The one common thread here for all the patches is that we also
scrap the .remove functions which would only be used for module
unload (impossible) and driver unbind.  For the drivers here, there
doesn't seem to be a sensible unbind use case (vs. e.g. a multiport
PCI ethernet driver where one port is unbound and passed through to
a kvm guest or similar).  Hence we just explicitly disallow any
driver unbind operations to help prevent root from doing something
illogical to the machine that they could have done previously.

We've already done this for drivers/tty/serial/mpsc.c previously.

Build tested for allmodconfig on ARM64 and powerpc for tty/tty-testing.

Paul.

---

Cc: Andy Gross <redacted>
Cc: Anton Blanchard <redacted>
Cc: David Brown <redacted>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <redacted>
Cc: Kumar Gala <redacted>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicolas Ferre <redacted>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-arm-msm@vger.kernel.org
Cc: linux-mediatek@lists.infradead.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-serial@vger.kernel.org
Cc: linux-soc@vger.kernel.org

Paul Gortmaker (5):
  drivers/tty: make hvc/hvc_vio.c explicitly non-modular
  drivers/tty: make ehv_bytechan.c explicitly non-modular
  drivers/tty/serial: make serial/atmel_serial.c explicitly non-modular
  drivers/tty/serial: make msm_serial.c explicitly non-modular
  drivers/tty/serial: make 8250/8250_mtk.c explicitly non-modular

 drivers/tty/ehv_bytechan.c         | 40 +++------------------------------
 drivers/tty/hvc/hvc_vio.c          | 29 ++++--------------------
 drivers/tty/serial/8250/8250_mtk.c | 35 ++++++-----------------------
 drivers/tty/serial/atmel_serial.c  | 45 ++++----------------------------------
 drivers/tty/serial/msm_serial.c    | 30 ++++---------------------
 5 files changed, 22 insertions(+), 157 deletions(-)

-- 
2.6.1

The Kconfig currently controlling compilation of this code is:

drivers/tty/Kconfig:config PPC_EPAPR_HV_BYTECHAN
drivers/tty/Kconfig:    bool "ePAPR hypervisor byte channel driver"

...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_init translates to device_initcall in the non-modular
case, 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <redacted>
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Paul Gortmaker <redacted>
---
 drivers/tty/ehv_bytechan.c | 40 +++-------------------------------------
 1 file changed, 3 insertions(+), 37 deletions(-)

diff --git a/drivers/tty/ehv_bytechan.c b/drivers/tty/ehv_bytechan.c
index 342b36b9ad35..7ac9bcdf1e61 100644
--- a/drivers/tty/ehv_bytechan.c
+++ b/drivers/tty/ehv_bytechan.c

@@ -23,7 +23,6 @@
  * byte channel used for the console is designated as the default tty.
  */
 
-#include <linux/module.h>
 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/err.h>

@@ -719,19 +718,6 @@ error:
 	return ret;
 }
 
-static int ehv_bc_tty_remove(struct platform_device *pdev)
-{
-	struct ehv_bc_data *bc = dev_get_drvdata(&pdev->dev);
-
-	tty_unregister_device(ehv_bc_driver, bc - bcs);
-
-	tty_port_destroy(&bc->port);
-	irq_dispose_mapping(bc->tx_irq);
-	irq_dispose_mapping(bc->rx_irq);
-
-	return 0;
-}
-
 static const struct of_device_id ehv_bc_tty_of_ids[] = {
 	{ .compatible = "epapr,hv-byte-channel" },
 	{}

@@ -741,15 +727,15 @@ static struct platform_driver ehv_bc_tty_driver = {
 	.driver = {
 		.name = "ehv-bc",
 		.of_match_table = ehv_bc_tty_of_ids,
+		.suppress_bind_attrs = true,
 	},
 	.probe		= ehv_bc_tty_probe,
-	.remove		= ehv_bc_tty_remove,
 };
 
 /**
  * ehv_bc_init - ePAPR hypervisor byte channel driver initialization
  *
- * This function is called when this module is loaded.
+ * This function is called when this driver is loaded.
  */
 static int __init ehv_bc_init(void)
 {

@@ -814,24 +800,4 @@ error:
 
 	return ret;
 }
-
-
-/**
- * ehv_bc_exit - ePAPR hypervisor byte channel driver termination
- *
- * This function is called when this driver is unloaded.
- */
-static void __exit ehv_bc_exit(void)
-{
-	platform_driver_unregister(&ehv_bc_tty_driver);
-	tty_unregister_driver(ehv_bc_driver);
-	put_tty_driver(ehv_bc_driver);
-	kfree(bcs);
-}
-
-module_init(ehv_bc_init);
-module_exit(ehv_bc_exit);
-
-MODULE_AUTHOR("Timur Tabi <timur@freescale.com>");
-MODULE_DESCRIPTION("ePAPR hypervisor byte channel driver");
-MODULE_LICENSE("GPL v2");
+device_initcall(ehv_bc_init);

-- 
2.6.1

The Kconfig currently controlling compilation of this code is:

drivers/tty/hvc/Kconfig:config HVC_CONSOLE
drivers/tty/hvc/Kconfig:        bool "pSeries Hypervisor Virtual Console 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.

Since module_init translates to device_initcall in the non-modular
case, the init ordering remains unchanged with this commit.

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.

We don't replace module.h with init.h since the file already has that.

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

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <redacted>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Anton Blanchard <redacted>
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Paul Gortmaker <redacted>
---
 drivers/tty/hvc/hvc_vio.c | 29 ++++-------------------------
 1 file changed, 4 insertions(+), 25 deletions(-)

diff --git a/drivers/tty/hvc/hvc_vio.c b/drivers/tty/hvc/hvc_vio.c
index f575a9b5ede7..b05dc5086627 100644
--- a/drivers/tty/hvc/hvc_vio.c
+++ b/drivers/tty/hvc/hvc_vio.c

@@ -41,7 +41,6 @@
 #include <linux/delay.h>
 #include <linux/slab.h>
 #include <linux/console.h>
-#include <linux/module.h>
 
 #include <asm/hvconsole.h>
 #include <asm/vio.h>

@@ -61,7 +60,6 @@ static struct vio_device_id hvc_driver_table[] = {
 #endif
 	{ "", "" }
 };
-MODULE_DEVICE_TABLE(vio, hvc_driver_table);
 
 typedef enum hv_protocol {
 	HV_PROTOCOL_RAW,

@@ -363,26 +361,13 @@ static int hvc_vio_probe(struct vio_dev *vdev,
 	return 0;
 }
 
-static int hvc_vio_remove(struct vio_dev *vdev)
-{
-	struct hvc_struct *hp = dev_get_drvdata(&vdev->dev);
-	int rc, termno;
-
-	termno = hp->vtermno;
-	rc = hvc_remove(hp);
-	if (rc == 0) {
-		if (hvterm_privs[termno] != &hvterm_priv0)
-			kfree(hvterm_privs[termno]);
-		hvterm_privs[termno] = NULL;
-	}
-	return rc;
-}
-
 static struct vio_driver hvc_vio_driver = {
 	.id_table	= hvc_driver_table,
 	.probe		= hvc_vio_probe,
-	.remove		= hvc_vio_remove,
 	.name		= hvc_driver_name,
+	.driver = {
+		.suppress_bind_attrs	= true,
+	},
 };
 
 static int __init hvc_vio_init(void)

@@ -394,13 +379,7 @@ static int __init hvc_vio_init(void)
 
 	return rc;
 }
-module_init(hvc_vio_init); /* after drivers/char/hvc_console.c */
-
-static void __exit hvc_vio_exit(void)
-{
-	vio_unregister_driver(&hvc_vio_driver);
-}
-module_exit(hvc_vio_exit);
+device_initcall(hvc_vio_init); /* after drivers/tty/hvc/hvc_console.c */
 
 void __init hvc_vio_init_early(void)
 {

-- 
2.6.1

On 18/10/2015 at 18:21:13 -0400, Paul Gortmaker wrote :

The one common thread here for all the patches is that we also
scrap the .remove functions which would only be used for module
unload (impossible) and driver unbind.  For the drivers here, there
doesn't seem to be a sensible unbind use case (vs. e.g. a multiport
PCI ethernet driver where one port is unbound and passed through to
a kvm guest or similar).  Hence we just explicitly disallow any
driver unbind operations to help prevent root from doing something
illogical to the machine that they could have done previously.

We've already done this for drivers/tty/serial/mpsc.c previously.

Build tested for allmodconfig on ARM64 and powerpc for tty/tty-testing.

So, how does this actually build test atmel_serial?

A proper solution would be to actually make it a tristate and allow
building as a module. I think it currently fails because of
console_initcall() but that is certainly fixable.


-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

[Re: [PATCH 0/5] drivers/tty: make more bool drivers explicitly non-modular] On 20/10/2015 (Tue 17:10) Alexandre Belloni wrote:

On 18/10/2015 at 18:21:13 -0400, Paul Gortmaker wrote :

quoted

The one common thread here for all the patches is that we also
scrap the .remove functions which would only be used for module
unload (impossible) and driver unbind.  For the drivers here, there
doesn't seem to be a sensible unbind use case (vs. e.g. a multiport
PCI ethernet driver where one port is unbound and passed through to
a kvm guest or similar).  Hence we just explicitly disallow any
driver unbind operations to help prevent root from doing something
illogical to the machine that they could have done previously.

We've already done this for drivers/tty/serial/mpsc.c previously.

Build tested for allmodconfig on ARM64 and powerpc for tty/tty-testing.

So, how does this actually build test atmel_serial?

Not sure why this should be a surprise;  I build test it exactly like this:

paul@builder-02:~/git/linux-head$ echo $ARCH
arm64
paul@builder-02:~/git/linux-head$ echo $CROSS_COMPILE 
aarch64-linux-gnu-
paul@builder-02:~/git/linux-head$ make O=../arm-build/  drivers/tty/serial/atmel_serial.o
make[1]: Entering directory '/home/paul/git/arm-build'
arch/arm64/Makefile:25: LSE atomics not supported by binutils
  CHK     include/config/kernel.release
  Using /home/paul/git/linux-head as source for kernel
  GEN     ./Makefile
  CHK     include/generated/uapi/linux/version.h
  CHK     include/generated/utsrelease.h

[...]

  HOSTCC  scripts/sign-file
  HOSTCC  scripts/extract-cert
  CC      drivers/tty/serial/atmel_serial.o
make[1]: Leaving directory '/home/paul/git/arm-build'
paul@builder-02:~/git/linux-head$ 

It did build; no warning/error.  Would you call it an invalid build test?

A proper solution would be to actually make it a tristate and allow
building as a module. I think it currently fails because of
console_initcall() but that is certainly fixable.

Well, as per other threads on this topic, if people want to extend
the functionality to support tristate, then great.  But please do
not confuse that with existing functionality which is clearly non
modular in this case.

Thanks,
Paul.
--

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

On 20/10/2015 at 20:20:07 -0400, Paul Gortmaker wrote :

[Re: [PATCH 0/5] drivers/tty: make more bool drivers explicitly non-modular] On 20/10/2015 (Tue 17:10) Alexandre Belloni wrote:

quoted

On 18/10/2015 at 18:21:13 -0400, Paul Gortmaker wrote :

quoted

The one common thread here for all the patches is that we also
scrap the .remove functions which would only be used for module
unload (impossible) and driver unbind.  For the drivers here, there
doesn't seem to be a sensible unbind use case (vs. e.g. a multiport
PCI ethernet driver where one port is unbound and passed through to
a kvm guest or similar).  Hence we just explicitly disallow any
driver unbind operations to help prevent root from doing something
illogical to the machine that they could have done previously.

We've already done this for drivers/tty/serial/mpsc.c previously.

Build tested for allmodconfig on ARM64 and powerpc for tty/tty-testing.

So, how does this actually build test atmel_serial?

Not sure why this should be a surprise;  I build test it exactly like this:

CONFIG_SERIAL_ATMEL is not selected by allmodconfig on arm64 or powerpc
so this is not explaining how you build tested atmel_serial.

paul@builder-02:~/git/linux-head$ echo $ARCH
arm64
paul@builder-02:~/git/linux-head$ echo $CROSS_COMPILE 
aarch64-linux-gnu-
paul@builder-02:~/git/linux-head$ make O=../arm-build/  drivers/tty/serial/atmel_serial.o
make[1]: Entering directory '/home/paul/git/arm-build'
arch/arm64/Makefile:25: LSE atomics not supported by binutils
  CHK     include/config/kernel.release
  Using /home/paul/git/linux-head as source for kernel
  GEN     ./Makefile
  CHK     include/generated/uapi/linux/version.h
  CHK     include/generated/utsrelease.h

[...]

  HOSTCC  scripts/sign-file
  HOSTCC  scripts/extract-cert
  CC      drivers/tty/serial/atmel_serial.o
make[1]: Leaving directory '/home/paul/git/arm-build'
paul@builder-02:~/git/linux-head$ 

It did build; no warning/error.  Would you call it an invalid build test?

What you describe is a different test. I end up with 4 warnings when
doing that on my machine.

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

[[PATCH 0/5] drivers/tty: make more bool drivers explicitly non-modular] On 18/10/2015 (Sun 18:21) Paul Gortmaker wrote:

This next set of patches to drivers/tty fixes up more drivers that would
perhaps appear modular when looking at the code, but are controlled by
a bool Kconfig.  We make sure they don't look modular and get rid
of module related code in the drivers that would never be used.

[...]

Paul Gortmaker (5):
  drivers/tty: make hvc/hvc_vio.c explicitly non-modular
  drivers/tty: make ehv_bytechan.c explicitly non-modular
  drivers/tty/serial: make serial/atmel_serial.c explicitly non-modular
  drivers/tty/serial: make msm_serial.c explicitly non-modular
  drivers/tty/serial: make 8250/8250_mtk.c explicitly non-modular

Hi Greg,

You've merged the #3 atmel patch and #5 the 8250_mtk patch; the msm_serial
patch (#4) is no longer applicable since the authors changed it to tristate.

That leaves the top two patches; both for PPC hardware.  Did you skip
those because you wanted them pushed through the powerpc tree?

If so, that is fine, I can do that.  Just let me know.

Thanks,
Paul.
--

 drivers/tty/ehv_bytechan.c         | 40 +++------------------------------
 drivers/tty/hvc/hvc_vio.c          | 29 ++++--------------------
 drivers/tty/serial/8250/8250_mtk.c | 35 ++++++-----------------------
 drivers/tty/serial/atmel_serial.c  | 45 ++++----------------------------------
 drivers/tty/serial/msm_serial.c    | 30 ++++---------------------
 5 files changed, 22 insertions(+), 157 deletions(-)

-- 
2.6.1