[PATCH] ARM: Dove: allow PCI to be disabled

[PATCH] ARM: Dove: allow PCI to be disabled

[Russell King - ARM Linux]

Allow PCI support for Dove to be disabled.  Some platforms do not have
anything connected to the PCIe ports, so requiring PCI support to be
built into the kernel just wastes space, and presents a lot more config
options than are necessary.

However, select USB_ARCH_HAS_EHCI so that we can still have EHCI
support.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
 arch/arm/Kconfig            |    3 ++-
 arch/arm/mach-dove/Makefile |    3 ++-
 arch/arm/mach-dove/common.h |    4 ++++
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 27f5b2c..344d40e 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -536,14 +536,15 @@ config ARCH_IXP4XX
 config ARCH_DOVE
 	bool "Marvell Dove"
 	select CPU_V7
-	select PCI
 	select ARCH_REQUIRE_GPIOLIB
 	select GENERIC_CLOCKEVENTS
+	select MIGHT_HAVE_PCI
 	select NEED_MACH_IO_H
 	select PLAT_ORION
 	select CLKDEV_LOOKUP
 	select NEED_MACH_MEMORY_H
 	select COMMON_CLK
+	select USB_ARCH_HAS_EHCI
 	help
 	  Support for the Marvell Dove SoC 88AP510
 
diff --git a/arch/arm/mach-dove/Makefile b/arch/arm/mach-dove/Makefile
index 7d89269..b5a5773 100644
--- a/arch/arm/mach-dove/Makefile
+++ b/arch/arm/mach-dove/Makefile
@@ -1,4 +1,5 @@
-obj-y				+= common.o addr-map.o irq.o pcie.o mpp.o clock.o dump_cp15_regs.o
+obj-y				+= common.o addr-map.o irq.o mpp.o clock.o dump_cp15_regs.o
+obj-$(CONFIG_PCI)		+= pcie.o
 
 obj-$(CONFIG_MACH_DOVE_DB)	+= dove-db-setup.o
 obj-$(CONFIG_MACH_CM_A510)	+= cm-a510.o
diff --git a/arch/arm/mach-dove/common.h b/arch/arm/mach-dove/common.h
index 2ea271d..17404a0 100644
--- a/arch/arm/mach-dove/common.h
+++ b/arch/arm/mach-dove/common.h
@@ -29,7 +29,11 @@ void dove_setup_cpu_mbus(void);
 void dove_ge00_init(struct mv643xx_eth_platform_data *eth_data);
 void dove_hwmon_init(void);
 void dove_sata_init(struct mv_sata_platform_data *sata_data);
+#ifdef CONfig_PCI
 void dove_pcie_init(int init_port0, int init_port1);
+#else
+static inline void dove_pcie_init(int init_port0, int init_port1) { }
+#endif
 void dove_ehci0_init(void);
 void dove_ehci1_init(void);
 void dove_uart0_init(void);

[PATCH] ARM: Dove: allow PCI to be disabled

[Jason Cooper]

On Wed, Aug 15, 2012 at 09:57:09AM +0100, Russell King - ARM Linux wrote:
> Allow PCI support for Dove to be disabled.  Some platforms do not have
> anything connected to the PCIe ports, so requiring PCI support to be
> built into the kernel just wastes space, and presents a lot more config
> options than are necessary.
> 
> However, select USB_ARCH_HAS_EHCI so that we can still have EHCI
> support.
> 
> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
> ---
>  arch/arm/Kconfig            |    3 ++-
>  arch/arm/mach-dove/Makefile |    3 ++-
>  arch/arm/mach-dove/common.h |    4 ++++
>  3 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 27f5b2c..344d40e 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -536,14 +536,15 @@ config ARCH_IXP4XX
>  config ARCH_DOVE
>  	bool "Marvell Dove"
>  	select CPU_V7
> -	select PCI
>  	select ARCH_REQUIRE_GPIOLIB
>  	select GENERIC_CLOCKEVENTS
> +	select MIGHT_HAVE_PCI
>  	select NEED_MACH_IO_H
>  	select PLAT_ORION
>  	select CLKDEV_LOOKUP
>  	select NEED_MACH_MEMORY_H
>  	select COMMON_CLK
> +	select USB_ARCH_HAS_EHCI
>  	help
>  	  Support for the Marvell Dove SoC 88AP510
>  
> diff --git a/arch/arm/mach-dove/Makefile b/arch/arm/mach-dove/Makefile
> index 7d89269..b5a5773 100644
> --- a/arch/arm/mach-dove/Makefile
> +++ b/arch/arm/mach-dove/Makefile
> @@ -1,4 +1,5 @@
> -obj-y				+= common.o addr-map.o irq.o pcie.o mpp.o clock.o dump_cp15_regs.o
> +obj-y				+= common.o addr-map.o irq.o mpp.o clock.o dump_cp15_regs.o
> +obj-$(CONFIG_PCI)		+= pcie.o
>  
>  obj-$(CONFIG_MACH_DOVE_DB)	+= dove-db-setup.o
>  obj-$(CONFIG_MACH_CM_A510)	+= cm-a510.o
> diff --git a/arch/arm/mach-dove/common.h b/arch/arm/mach-dove/common.h
> index 2ea271d..17404a0 100644
> --- a/arch/arm/mach-dove/common.h
> +++ b/arch/arm/mach-dove/common.h
> @@ -29,7 +29,11 @@ void dove_setup_cpu_mbus(void);
>  void dove_ge00_init(struct mv643xx_eth_platform_data *eth_data);
>  void dove_hwmon_init(void);
>  void dove_sata_init(struct mv_sata_platform_data *sata_data);
> +#ifdef CONfig_PCI

ummm...   ^^^^^^ is this a typo?  (/me dives into a trench)

>  void dove_pcie_init(int init_port0, int init_port1);
> +#else
> +static inline void dove_pcie_init(int init_port0, int init_port1) { }
> +#endif
>  void dove_ehci0_init(void);
>  void dove_ehci1_init(void);
>  void dove_uart0_init(void);

thx,

Jason.

[PATCH] ARM: Dove: allow PCI to be disabled

[Russell King - ARM Linux]

On Wed, Aug 15, 2012 at 08:18:01AM -0400, Jason Cooper wrote:
> On Wed, Aug 15, 2012 at 09:57:09AM +0100, Russell King - ARM Linux wrote:
> > +#ifdef CONfig_PCI
> 
> ummm...   ^^^^^^ is this a typo?  (/me dives into a trench)

No, it's your imagination playing tricks again. :)  I'll get a new patch
out when I'm in a state that I can redo the git commit without destroying
the current state of my development git tree.

(which may be a while as I'm trying to sort out why ubuntu 12.04 userspace
seems to be a total disaster on the cubox.)

[PATCH] ARM: Dove: allow PCI to be disabled

[Russell King]

Allow PCI support for Dove to be disabled.  Some platforms do not have
anything connected to the PCIe ports, so requiring PCI support to be
built into the kernel just wastes space, and presents a lot more config
options than are necessary.

However, select USB_ARCH_HAS_EHCI so that we can still have EHCI
support.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
 arch/arm/Kconfig            |    3 ++-
 arch/arm/mach-dove/Makefile |    3 ++-
 arch/arm/mach-dove/common.h |    4 ++++
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 27f5b2c..344d40e 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -536,14 +536,15 @@ config ARCH_IXP4XX
 config ARCH_DOVE
 	bool "Marvell Dove"
 	select CPU_V7
-	select PCI
 	select ARCH_REQUIRE_GPIOLIB
 	select GENERIC_CLOCKEVENTS
+	select MIGHT_HAVE_PCI
 	select NEED_MACH_IO_H
 	select PLAT_ORION
 	select CLKDEV_LOOKUP
 	select NEED_MACH_MEMORY_H
 	select COMMON_CLK
+	select USB_ARCH_HAS_EHCI
 	help
 	  Support for the Marvell Dove SoC 88AP510
 
diff --git a/arch/arm/mach-dove/Makefile b/arch/arm/mach-dove/Makefile
index 7d89269..b5a5773 100644
--- a/arch/arm/mach-dove/Makefile
+++ b/arch/arm/mach-dove/Makefile
@@ -1,4 +1,5 @@
-obj-y				+= common.o addr-map.o irq.o pcie.o mpp.o clock.o dump_cp15_regs.o
+obj-y				+= common.o addr-map.o irq.o mpp.o clock.o dump_cp15_regs.o
+obj-$(CONFIG_PCI)		+= pcie.o
 
 obj-$(CONFIG_MACH_DOVE_DB)	+= dove-db-setup.o
 obj-$(CONFIG_MACH_CM_A510)	+= cm-a510.o
diff --git a/arch/arm/mach-dove/common.h b/arch/arm/mach-dove/common.h
index 2ea271d..678ef0b 100644
--- a/arch/arm/mach-dove/common.h
+++ b/arch/arm/mach-dove/common.h
@@ -29,7 +29,11 @@ void dove_setup_cpu_mbus(void);
 void dove_ge00_init(struct mv643xx_eth_platform_data *eth_data);
 void dove_hwmon_init(void);
 void dove_sata_init(struct mv_sata_platform_data *sata_data);
+#ifdef CONFIG_PCI
 void dove_pcie_init(int init_port0, int init_port1);
+#else
+static inline void dove_pcie_init(int init_port0, int init_port1) { }
+#endif
 void dove_ehci0_init(void);
 void dove_ehci1_init(void);
 void dove_uart0_init(void);
-- 
1.7.4.4

[PATCH] ARM: Dove: allow PCI to be disabled

[Andrew Lunn]

On Sun, Sep 09, 2012 at 08:34:13PM +0100, Russell King wrote:
> Allow PCI support for Dove to be disabled.  Some platforms do not have
> anything connected to the PCIe ports, so requiring PCI support to be
> built into the kernel just wastes space, and presents a lot more config
> options than are necessary.
> 
> However, select USB_ARCH_HAS_EHCI so that we can still have EHCI
> support.

Hi Russel

I have a patch in GregKH usb-next which also ensures USB_ARCH_HAS_EHCI
is selected.

http://git.kernel.org/?p=linux/kernel/git/gregkh/usb.git;a=commitdiff;h=ba2f9dff6c914b91005f687a9d75c8eac110d323

So we might not need your select as well, although it does not harm.

   Andrew

[PATCH] ARM: Dove: allow PCI to be disabled

[Russell King - ARM Linux]

On Sun, Sep 09, 2012 at 10:47:05PM +0200, Andrew Lunn wrote:
> On Sun, Sep 09, 2012 at 08:34:13PM +0100, Russell King wrote:
> > Allow PCI support for Dove to be disabled.  Some platforms do not have
> > anything connected to the PCIe ports, so requiring PCI support to be
> > built into the kernel just wastes space, and presents a lot more config
> > options than are necessary.
> > 
> > However, select USB_ARCH_HAS_EHCI so that we can still have EHCI
> > support.
> 
> Hi Russel
> 
> I have a patch in GregKH usb-next which also ensures USB_ARCH_HAS_EHCI
> is selected.
> 
> http://git.kernel.org/?p=linux/kernel/git/gregkh/usb.git;a=commitdiff;h=ba2f9dff6c914b91005f687a9d75c8eac110d323
> 
> So we might not need your select as well, although it does not harm.

That depends on how this patch is handled.  If it gets into mainline via
a separate path to GregKH's USB tree, then it must be kept together as
otherwise it _will_ cause regressions - namely EHCI becomes impossible
to select when PCI=n.  That in turn makes the CuBox (and probably other
Dove platforms) a rather useless display-only platform...

[PATCH] ARM: Dove: allow PCI to be disabled

[Jason Cooper]

On Sun, Sep 09, 2012 at 09:55:21PM +0100, Russell King - ARM Linux wrote:
> On Sun, Sep 09, 2012 at 10:47:05PM +0200, Andrew Lunn wrote:
> > On Sun, Sep 09, 2012 at 08:34:13PM +0100, Russell King wrote:
> > > Allow PCI support for Dove to be disabled.  Some platforms do not have
> > > anything connected to the PCIe ports, so requiring PCI support to be
> > > built into the kernel just wastes space, and presents a lot more config
> > > options than are necessary.
> > > 
> > > However, select USB_ARCH_HAS_EHCI so that we can still have EHCI
> > > support.
> > 
> > Hi Russel
> > 
> > I have a patch in GregKH usb-next which also ensures USB_ARCH_HAS_EHCI
> > is selected.
> > 
> > http://git.kernel.org/?p=linux/kernel/git/gregkh/usb.git;a=commitdiff;h=ba2f9dff6c914b91005f687a9d75c8eac110d323
> > 
> > So we might not need your select as well, although it does not harm.
> 
> That depends on how this patch is handled.  If it gets into mainline via
> a separate path to GregKH's USB tree, then it must be kept together as
> otherwise it _will_ cause regressions - namely EHCI becomes impossible
> to select when PCI=n.  That in turn makes the CuBox (and probably other
> Dove platforms) a rather useless di
[message trucated, I need to working on file locking for my email
auto-flagging script... :-/]

greg just pulled Andrew's patch into his usb tree within the past few
days.  Russell, would you prefer to submit this to greg's usb tree, or
resend without USB_ARCH_HAS_EHCI?

thx,

Jason.

[PATCH] ARM: Dove: allow PCI to be disabled

[Russell King - ARM Linux]

On Sun, Sep 09, 2012 at 05:01:26PM -0400, Jason Cooper wrote:
> On Sun, Sep 09, 2012 at 09:55:21PM +0100, Russell King - ARM Linux wrote:
> > On Sun, Sep 09, 2012 at 10:47:05PM +0200, Andrew Lunn wrote:
> > > On Sun, Sep 09, 2012 at 08:34:13PM +0100, Russell King wrote:
> > > > Allow PCI support for Dove to be disabled.  Some platforms do not have
> > > > anything connected to the PCIe ports, so requiring PCI support to be
> > > > built into the kernel just wastes space, and presents a lot more config
> > > > options than are necessary.
> > > > 
> > > > However, select USB_ARCH_HAS_EHCI so that we can still have EHCI
> > > > support.
> > > 
> > > Hi Russel
> > > 
> > > I have a patch in GregKH usb-next which also ensures USB_ARCH_HAS_EHCI
> > > is selected.
> > > 
> > > http://git.kernel.org/?p=linux/kernel/git/gregkh/usb.git;a=commitdiff;h=ba2f9dff6c914b91005f687a9d75c8eac110d323
> > > 
> > > So we might not need your select as well, although it does not harm.
> > 
> > That depends on how this patch is handled.  If it gets into mainline via
> > a separate path to GregKH's USB tree, then it must be kept together as
> > otherwise it _will_ cause regressions - namely EHCI becomes impossible
> > to select when PCI=n.  That in turn makes the CuBox (and probably other
> > Dove platforms) a rather useless di
> [message trucated, I need to working on file locking for my email
> auto-flagging script... :-/]
> 
> greg just pulled Andrew's patch into his usb tree within the past few
> days.  Russell, would you prefer to submit this to greg's usb tree, or
> resend without USB_ARCH_HAS_EHCI?

I thought I'd already answered the latter point.

As I said, it breaks the patch to remove that select, so it can not be
removed.  Removing it will create regressions - can I be any more clear
about that.  So no, I will not remove that select statement because I
can't without _breaking_ my Dove builds here.

I don't think submitting this patch to Greg's USB tree is also appropriate
either, it's clearly ARM specific in nature, or even PCI specific.  It
isn't a USB patch.  Neither is a patch changing a USB setting in
arch/arm/Kconfig.  If any tree, these patches should be going through
arm-soc.

[PATCH] ARM: Dove: allow PCI to be disabled

[Jason Cooper]

On Mon, Sep 10, 2012 at 01:45:11AM +0100, Russell King - ARM Linux wrote:
> On Sun, Sep 09, 2012 at 05:01:26PM -0400, Jason Cooper wrote:
> > On Sun, Sep 09, 2012 at 09:55:21PM +0100, Russell King - ARM Linux wrote:
> > > On Sun, Sep 09, 2012 at 10:47:05PM +0200, Andrew Lunn wrote:
> > > > On Sun, Sep 09, 2012 at 08:34:13PM +0100, Russell King wrote:
> > > > > Allow PCI support for Dove to be disabled.  Some platforms do not have
> > > > > anything connected to the PCIe ports, so requiring PCI support to be
> > > > > built into the kernel just wastes space, and presents a lot more config
> > > > > options than are necessary.
> > > > > 
> > > > > However, select USB_ARCH_HAS_EHCI so that we can still have EHCI
> > > > > support.
> > > > 
> > > > Hi Russel
> > > > 
> > > > I have a patch in GregKH usb-next which also ensures USB_ARCH_HAS_EHCI
> > > > is selected.
> > > > 
> > > > http://git.kernel.org/?p=linux/kernel/git/gregkh/usb.git;a=commitdiff;h=ba2f9dff6c914b91005f687a9d75c8eac110d323
> > > > 
> > > > So we might not need your select as well, although it does not harm.
> > > 
> > > That depends on how this patch is handled.  If it gets into mainline via
> > > a separate path to GregKH's USB tree, then it must be kept together as
> > > otherwise it _will_ cause regressions - namely EHCI becomes impossible
> > > to select when PCI=n.  That in turn makes the CuBox (and probably other
> > > Dove platforms) a rather useless di
> > [message trucated, I need to working on file locking for my email
> > auto-flagging script... :-/]
> > 
> > greg just pulled Andrew's patch into his usb tree within the past few
> > days.  Russell, would you prefer to submit this to greg's usb tree, or
> > resend without USB_ARCH_HAS_EHCI?
> 
> I thought I'd already answered the latter point.
> 
> As I said, it breaks the patch to remove that select, so it can not be
> removed.  Removing it will create regressions - can I be any more clear
> about that.  So no, I will not remove that select statement because I
> can't without _breaking_ my Dove builds here.

My apologies.  I was simply trying to achieve the cleanest solution.
Andrew's patch selects USB_ARCH_HAS_EHCI whenever PLAT_ORION is enabled,
of which dove is one.  Purely from the pov of the code, this makes the
select redundant.

iiuc, the regression you are refering to would occur iff this patch
(without the select) makes it into mainline _before_ Andrew's patch in
Greg's tree.  As I haven't pulled this patch yet, I can add a dependency
in the tag message listing the patch in gregkh's usb tree.  Arnd and
Olof would heed this and make sure this patch comes after Andrews.  This
should prevent the regression.

If the above is true, then indeed, the select is not necessary.  Is
there something else I'm missing?

> I don't think submitting this patch to Greg's USB tree is also
> appropriate either, it's clearly ARM specific in nature, or even PCI
> specific.  It isn't a USB patch.

Agreed, please chalk that up to new maintainer crack-smoking. :-)

> Neither is a patch changing a USB setting in arch/arm/Kconfig.  If any
> tree, these patches should be going through arm-soc.

Agreed.

thx,

Jason.

[PATCH] ARM: Dove: allow PCI to be disabled

[Russell King - ARM Linux]

On Sun, Sep 09, 2012 at 09:44:22PM -0400, Jason Cooper wrote:
> iiuc, the regression you are refering to would occur iff this patch
> (without the select) makes it into mainline _before_ Andrew's patch in
> Greg's tree.  As I haven't pulled this patch yet, I can add a dependency
> in the tag message listing the patch in gregkh's usb tree.

For the regression to occur, you need to land on a commit in the tree
where this patch (without the select) is in the history but not the
patch in Greg's tree.

The commit history remains a series of independent branches even after
trees are merged into Linus' tree - there is _no_ linearisation of the
history in git.

This means when anyone comes to use git bisect, they _can_ land on any
commit in any branch, which means if this patch and the other patch
take two different routes, and this patch does not have the select, you
_will_ hit the regression.

Let me illustrate:

---A----B----C----D---...---E----M
   `--G----H----I----J---...---K-'

Let's say A-E is Greg's tree, and D is the commit you are talking about.
Let's say G-K is Arnd's tree, and H is my patch without the 'select'
statement.  Let's also say that '...' in each case includes a significant
number of commits.

If, through a git bisect (or manual commit selection) you end up trying
to build at any commit I to K, you will not be builting a tree with D
in, but you will be building a tree with H in.  You end up with EHCI
being disabled in your configuration.

What this also means is that when building Arnd's tree without Greg's tree,
you will also end up with EHCI disabled in those configurations (because
you also don't have commit D.)

See?  There is no such thing as "lets make sure tree X gets merged before
tree Y because commit A depends on commit B".  That "solution" doesn't fix
any dependency between the two commits - it merely gives the impression
that it does because you're looking only at the result.

That kind of solution is broken thinking.

> Arnd and
> Olof would heed this and make sure this patch comes after Andrews.  This
> should prevent the regression.

As you can see from the above, tree order does not solve these issues.
It gives the impression from the final result that it does, but it
doesn't.  It breaks at least our most powerful regression debug tool -
git bisect.

[PATCH] ARM: Dove: allow PCI to be disabled

[Nicolas Pitre]

On Sun, 9 Sep 2012, Jason Cooper wrote:

> On Mon, Sep 10, 2012 at 01:45:11AM +0100, Russell King - ARM Linux wrote:
> > On Sun, Sep 09, 2012 at 05:01:26PM -0400, Jason Cooper wrote:
> > > On Sun, Sep 09, 2012 at 09:55:21PM +0100, Russell King - ARM Linux wrote:
> > > > On Sun, Sep 09, 2012 at 10:47:05PM +0200, Andrew Lunn wrote:
> > > > > On Sun, Sep 09, 2012 at 08:34:13PM +0100, Russell King wrote:
> > > > > > Allow PCI support for Dove to be disabled.  Some platforms do not have
> > > > > > anything connected to the PCIe ports, so requiring PCI support to be
> > > > > > built into the kernel just wastes space, and presents a lot more config
> > > > > > options than are necessary.
> > > > > > 
> > > > > > However, select USB_ARCH_HAS_EHCI so that we can still have EHCI
> > > > > > support.
> > > > > 
> > > > > Hi Russel
> > > > > 
> > > > > I have a patch in GregKH usb-next which also ensures USB_ARCH_HAS_EHCI
> > > > > is selected.
> > > > > 
> > > > > http://git.kernel.org/?p=linux/kernel/git/gregkh/usb.git;a=commitdiff;h=ba2f9dff6c914b91005f687a9d75c8eac110d323
> > > > > 
> > > > > So we might not need your select as well, although it does not harm.
> > > > 
> > > > That depends on how this patch is handled.  If it gets into mainline via
> > > > a separate path to GregKH's USB tree, then it must be kept together as
> > > > otherwise it _will_ cause regressions - namely EHCI becomes impossible
> > > > to select when PCI=n.  That in turn makes the CuBox (and probably other
> > > > Dove platforms) a rather useless di
> > > [message trucated, I need to working on file locking for my email
> > > auto-flagging script... :-/]
> > > 
> > > greg just pulled Andrew's patch into his usb tree within the past few
> > > days.  Russell, would you prefer to submit this to greg's usb tree, or
> > > resend without USB_ARCH_HAS_EHCI?
> > 
> > I thought I'd already answered the latter point.
> > 
> > As I said, it breaks the patch to remove that select, so it can not be
> > removed.  Removing it will create regressions - can I be any more clear
> > about that.  So no, I will not remove that select statement because I
> > can't without _breaking_ my Dove builds here.
> 
> My apologies.  I was simply trying to achieve the cleanest solution.
> Andrew's patch selects USB_ARCH_HAS_EHCI whenever PLAT_ORION is enabled,
> of which dove is one.  Purely from the pov of the code, this makes the
> select redundant.

Are we trying to split hairs here?

At best, the select will be redundant and that is trivially cleaned up 
later.  At worst, you'll have a trivial git merge conflict to solve (and 
that happens all the time).

So the simplest thing to do is to keep the select there to prevent build 
issues and remember that perfection is the enemy of the good.


Nicolas

[PATCH] ARM: Dove: allow PCI to be disabled

[Nicolas Pitre]

On Mon, 10 Sep 2012, Russell King - ARM Linux wrote:

> On Sun, Sep 09, 2012 at 09:44:22PM -0400, Jason Cooper wrote:
> > iiuc, the regression you are refering to would occur iff this patch
> > (without the select) makes it into mainline _before_ Andrew's patch in
> > Greg's tree.  As I haven't pulled this patch yet, I can add a dependency
> > in the tag message listing the patch in gregkh's usb tree.
> 
> For the regression to occur, you need to land on a commit in the tree
> where this patch (without the select) is in the history but not the
> patch in Greg's tree.
> 
> The commit history remains a series of independent branches even after
> trees are merged into Linus' tree - there is _no_ linearisation of the
> history in git.

@Jason:

The dependency tracking done in the arm-soc tree performed by Arnd and 
Olof is merely a way for you to _base_ your branch on top of other 
people's branch before they pull it from you.  For example, you may 
decide to build your branch on top of Greg's to get some prerequisite 
commits for your work. In that case the goal for the arm-soc maintainers 
is to avoid the situation where a pull of the arm-soc tree into mainline 
would also pull greg's stuff without his asking for it.


Nicolas

[PATCH] ARM: Dove: allow PCI to be disabled

[Jason Cooper]

On Mon, Sep 10, 2012 at 12:45:10PM -0400, Nicolas Pitre wrote:
> So the simplest thing to do is to keep the select there to prevent build 
> issues and remember that perfection is the enemy of the good.

Yes, I have to remind myself of that a lot.  To the point I've
considered getting a tattoo of it somewhere.  :-)

You are right.  I was primarily trying to drill down on something I
didn't understand, which is how leaving out that line could cause a
regression.  The patch is fine, of course, I'll pull it in in my next
round.  Anything else in this thread will be purely me attempting to
make sure I fully understand git and the merge process wrt to causing
regressions.

thx,

Jason.

[PATCH] ARM: Dove: allow PCI to be disabled

[Jason Cooper]

On Mon, Sep 10, 2012 at 09:29:42AM +0100, Russell King - ARM Linux wrote:
> On Sun, Sep 09, 2012 at 09:44:22PM -0400, Jason Cooper wrote:
> > iiuc, the regression you are refering to would occur iff this patch
> > (without the select) makes it into mainline _before_ Andrew's patch in
> > Greg's tree.  As I haven't pulled this patch yet, I can add a dependency
> > in the tag message listing the patch in gregkh's usb tree.
> 
> For the regression to occur, you need to land on a commit in the tree
> where this patch (without the select) is in the history but not the
> patch in Greg's tree.
> 
> The commit history remains a series of independent branches even after
> trees are merged into Linus' tree - there is _no_ linearisation of the
> history in git.

<ding> (light comes on).  Thank you!  Somewhere in the time I've been
working with git I developed an incorrect assumption.  While
embarrassing, I'm glad I asked for clarification.

Anytime I view the merging of branches in my head, I always see gitg's
"all branches" view.  Since patches are sorted over time, I assumed they
became related that way once they were merged.  It sounds silly as I
type it out loud. :-)

It all makes sense now.

Thanks for taking the time to explain it so clearly,

Jason.