[PATCH v2 0/2] ACPI/PCI: export acpi_pci_root to find pci_bus correctly

[PATCH v2 0/2] ACPI/PCI: export acpi_pci_root to find pci_bus correctly

[Alex Chiang]

This is v2 of a patch series that:

	a) exports struct acpi_pci_root
	b) fixes an assumption in acpiphp about finding struct pci_bus

It's a minimal fix that's aimed at -rc4, as (b) fixes an assumption
introduced in -rc1.

I'll send the rest of the cleanups for linux-next later, after doing
some more testing.

Original thread here:
	http://thread.gmane.org/gmane.linux.kernel.pci/5080

v1 -> v2:
	- fixed build error in acpi_pci_root
	- reduced patch series in scope to be much smaller

---

Alex Chiang (2):
      ACPI: export acpi_pci_root and friends
      PCI Hotplug: acpiphp: get pci_bus from acpi handle correctly

 drivers/acpi/pci_root.c            |   17 ++---------------
 drivers/pci/hotplug/acpiphp_glue.c |   27 ++++++++++++++++-----------
 include/acpi/acpi_bus.h            |   16 ++++++++++++++++
 3 files changed, 34 insertions(+), 26 deletions(-)

[PATCH v2 1/2] ACPI: export acpi_pci_root and friends

[Alex Chiang]

We can simplify ACPI drivers if we can tell whether a handle is an
ACPI PCI root or not.

Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Alex Chiang <achiang@hp.com>
---

 drivers/acpi/pci_root.c |   17 ++---------------
 include/acpi/acpi_bus.h |   16 ++++++++++++++++
 2 files changed, 18 insertions(+), 15 deletions(-)

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index 55b5b90..31b961c 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -61,20 +61,6 @@ static struct acpi_driver acpi_pci_root_driver = {
 		},
 };
 
-struct acpi_pci_root {
-	struct list_head node;
-	struct acpi_device *device;
-	struct pci_bus *bus;
-	u16 segment;
-	u8 bus_nr;
-
-	u32 osc_support_set;	/* _OSC state of support bits */
-	u32 osc_control_set;	/* _OSC state of control bits */
-	u32 osc_control_qry;	/* the latest _OSC query result */
-
-	u32 osc_queried:1;	/* has _OSC control been queried? */
-};
-
 static LIST_HEAD(acpi_pci_roots);
 
 static struct acpi_pci_driver *sub_driver;
@@ -317,7 +303,7 @@ static acpi_status acpi_pci_osc_support(struct acpi_pci_root *root, u32 flags)
 	return status;
 }
 
-static struct acpi_pci_root *acpi_pci_find_root(acpi_handle handle)
+struct acpi_pci_root *acpi_pci_find_root(acpi_handle handle)
 {
 	struct acpi_pci_root *root;
 
@@ -327,6 +313,7 @@ static struct acpi_pci_root *acpi_pci_find_root(acpi_handle handle)
 	}
 	return NULL;
 }
+EXPORT_SYMBOL_GPL(acpi_pci_find_root);
 
 struct acpi_handle_node {
 	struct list_head node;
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index c65e4ce..c3ace75 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -369,10 +369,26 @@ int register_acpi_bus_type(struct acpi_bus_type *);
 int unregister_acpi_bus_type(struct acpi_bus_type *);
 struct device *acpi_get_physical_device(acpi_handle);
 
+struct acpi_pci_root {
+	struct list_head node;
+	struct acpi_device * device;
+	struct acpi_pci_id id;
+	struct pci_bus *bus;
+	u16 segment;
+	u8 bus_nr;
+
+	u32 osc_support_set;	/* _OSC state of support bits */
+	u32 osc_control_set;	/* _OSC state of control bits */
+	u32 osc_control_qry;	/* the latest _OSC query result */
+
+	u32 osc_queried:1;	/* has _OSC control been queried? */
+};
+
 /* helper */
 acpi_handle acpi_get_child(acpi_handle, acpi_integer);
 int acpi_is_root_bridge(acpi_handle);
 acpi_handle acpi_get_pci_rootbridge_handle(unsigned int, unsigned int);
+struct acpi_pci_root *acpi_pci_find_root(acpi_handle handle);
 #define DEVICE_ACPI_HANDLE(dev) ((acpi_handle)((dev)->archdata.acpi_handle))
 
 #ifdef CONFIG_PM_SLEEP

[PATCH v2 2/2] PCI Hotplug: acpiphp: get pci_bus from acpi handle correctly

[Alex Chiang]

We cannot simply call acpi_get_pci_dev() on any random ACPI handle
and hope that it works, because a PCI root bridge may not have
an associated struct pci_dev.

This is allowed per the PCI specification, and is referred to as a
non-materialized bridge.

So, depending on the type of PCI bridge that the handle points to,
use the appropriate interface to return the struct pci_bus correctly.

Signed-off-by: Alex Chiang <achiang@hp.com>
---

 drivers/pci/hotplug/acpiphp_glue.c |   27 ++++++++++++++++-----------
 1 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
index 0cb0f83..fa4658b 100644
--- a/drivers/pci/hotplug/acpiphp_glue.c
+++ b/drivers/pci/hotplug/acpiphp_glue.c
@@ -62,6 +62,21 @@ static void acpiphp_sanitize_bus(struct pci_bus *bus);
 static void acpiphp_set_hpp_values(acpi_handle handle, struct pci_bus *bus);
 static void handle_hotplug_event_func(acpi_handle handle, u32 type, void *context);
 
+static struct pci_bus *pci_bus_from_handle(acpi_handle handle)
+{
+	struct pci_bus *pbus;
+
+	if (acpi_is_root_bridge(handle)) {
+		struct acpi_pci_root *root = acpi_pci_find_root(handle);
+		pbus = root->bus;
+	} else {
+		struct pci_dev *pdev = acpi_get_pci_dev(handle);
+		pbus = pdev->subordinate;
+		pci_dev_put(pdev);
+	}
+	return pbus;
+}
+
 /* callback routine to check for the existence of a pci dock device */
 static acpi_status
 is_pci_dock_device(acpi_handle handle, u32 lvl, void *context, void **rv)
@@ -1387,16 +1402,7 @@ static void acpiphp_sanitize_bus(struct pci_bus *bus)
 /* Program resources in newly inserted bridge */
 static int acpiphp_configure_bridge (acpi_handle handle)
 {
-	struct pci_dev *dev;
-	struct pci_bus *bus;
-
-	dev = acpi_get_pci_dev(handle);
-	if (!dev) {
-		err("cannot get PCI domain and bus number for bridge\n");
-		return -EINVAL;
-	}
-
-	bus = dev->bus;
+	struct pci_bus *bus = pci_bus_from_handle(handle);
 
 	pci_bus_size_bridges(bus);
 	pci_bus_assign_resources(bus);
@@ -1404,7 +1410,6 @@ static int acpiphp_configure_bridge (acpi_handle handle)
 	acpiphp_set_hpp_values(handle, bus);
 	pci_enable_bridges(bus);
 	acpiphp_configure_ioapics(handle);
-	pci_dev_put(dev);
 	return 0;
 }
 

Re: [PATCH v2 2/2] PCI Hotplug: acpiphp: get pci_bus from acpi handle correctly

[Bjorn Helgaas]

On Tuesday 14 July 2009 02:53:33 pm Alex Chiang wrote:
> We cannot simply call acpi_get_pci_dev() on any random ACPI handle
> and hope that it works, because a PCI root bridge may not have
> an associated struct pci_dev.
> 
> This is allowed per the PCI specification, and is referred to as a
> non-materialized bridge.
> 
> So, depending on the type of PCI bridge that the handle points to,
> use the appropriate interface to return the struct pci_bus correctly.
> 
> Signed-off-by: Alex Chiang <achiang@hp.com>
> ---
> 
>  drivers/pci/hotplug/acpiphp_glue.c |   27 ++++++++++++++++-----------
>  1 files changed, 16 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
> index 0cb0f83..fa4658b 100644
> --- a/drivers/pci/hotplug/acpiphp_glue.c
> +++ b/drivers/pci/hotplug/acpiphp_glue.c
> @@ -62,6 +62,21 @@ static void acpiphp_sanitize_bus(struct pci_bus *bus);
>  static void acpiphp_set_hpp_values(acpi_handle handle, struct pci_bus *bus);
>  static void handle_hotplug_event_func(acpi_handle handle, u32 type, void *context);
>  
> +static struct pci_bus *pci_bus_from_handle(acpi_handle handle)
> +{
> +	struct pci_bus *pbus;
> +
> +	if (acpi_is_root_bridge(handle)) {
> +		struct acpi_pci_root *root = acpi_pci_find_root(handle);
> +		pbus = root->bus;
> +	} else {
> +		struct pci_dev *pdev = acpi_get_pci_dev(handle);
> +		pbus = pdev->subordinate;
> +		pci_dev_put(pdev);
> +	}
> +	return pbus;

I worry that acpi_is_root_bridge() merely checks the device IDs of
"handle", which isn't quite the same as checking whether the pci_root
driver has claimed "handle".

Are you confident that it's safe to move the pci_dev_put(), so it is
released before configuring the bridge?

What do you think about something like this (even though the get/put
is still a little clunky):

	struct pci_dev *dev = NULL;

	root = acpi_pci_find_root(handle);
	if (root)
		bus = root->bus;
	else {
		dev = acpi_get_pci_dev(handle);
		if (dev)
			bus = pdev->subordinate;
		else {
			err("cannot get PCI domain and bus number for bridge\n");
			return -EINVAL;
		}
	}

	pci_bus_size_bridges(bus);
	...
	if (dev)
		pci_dev_put(dev);
	return 0;

> +}
> +
>  /* callback routine to check for the existence of a pci dock device */
>  static acpi_status
>  is_pci_dock_device(acpi_handle handle, u32 lvl, void *context, void **rv)
> @@ -1387,16 +1402,7 @@ static void acpiphp_sanitize_bus(struct pci_bus *bus)
>  /* Program resources in newly inserted bridge */
>  static int acpiphp_configure_bridge (acpi_handle handle)
>  {
> -	struct pci_dev *dev;
> -	struct pci_bus *bus;
> -
> -	dev = acpi_get_pci_dev(handle);
> -	if (!dev) {
> -		err("cannot get PCI domain and bus number for bridge\n");
> -		return -EINVAL;
> -	}
> -
> -	bus = dev->bus;
> +	struct pci_bus *bus = pci_bus_from_handle(handle);
>  
>  	pci_bus_size_bridges(bus);
>  	pci_bus_assign_resources(bus);
> @@ -1404,7 +1410,6 @@ static int acpiphp_configure_bridge (acpi_handle handle)
>  	acpiphp_set_hpp_values(handle, bus);
>  	pci_enable_bridges(bus);
>  	acpiphp_configure_ioapics(handle);
> -	pci_dev_put(dev);
>  	return 0;
>  }

Re: [PATCH v2 2/2] PCI Hotplug: acpiphp: get pci_bus from acpi handle correctly

[Alex Chiang]

* Bjorn Helgaas <bjorn.helgaas@hp.com>:
> On Tuesday 14 July 2009 02:53:33 pm Alex Chiang wrote:
> > We cannot simply call acpi_get_pci_dev() on any random ACPI handle
> > and hope that it works, because a PCI root bridge may not have
> > an associated struct pci_dev.
> > 
> > This is allowed per the PCI specification, and is referred to as a
> > non-materialized bridge.
> > 
> > So, depending on the type of PCI bridge that the handle points to,
> > use the appropriate interface to return the struct pci_bus correctly.
> > 
> > Signed-off-by: Alex Chiang <achiang@hp.com>
> > ---
> > 
> >  drivers/pci/hotplug/acpiphp_glue.c |   27 ++++++++++++++++-----------
> >  1 files changed, 16 insertions(+), 11 deletions(-)
> > 
> > diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
> > index 0cb0f83..fa4658b 100644
> > --- a/drivers/pci/hotplug/acpiphp_glue.c
> > +++ b/drivers/pci/hotplug/acpiphp_glue.c
> > @@ -62,6 +62,21 @@ static void acpiphp_sanitize_bus(struct pci_bus *bus);
> >  static void acpiphp_set_hpp_values(acpi_handle handle, struct pci_bus *bus);
> >  static void handle_hotplug_event_func(acpi_handle handle, u32 type, void *context);
> >  
> > +static struct pci_bus *pci_bus_from_handle(acpi_handle handle)
> > +{
> > +	struct pci_bus *pbus;
> > +
> > +	if (acpi_is_root_bridge(handle)) {
> > +		struct acpi_pci_root *root = acpi_pci_find_root(handle);
> > +		pbus = root->bus;
> > +	} else {
> > +		struct pci_dev *pdev = acpi_get_pci_dev(handle);
> > +		pbus = pdev->subordinate;
> > +		pci_dev_put(pdev);
> > +	}
> > +	return pbus;
> 
> I worry that acpi_is_root_bridge() merely checks the device IDs of
> "handle", which isn't quite the same as checking whether the pci_root
> driver has claimed "handle".

Hm, I understand this concern in a theoretical sense, but could
you explain more of what you're thinking about, and give me a
concrete example of something that might go wrong here?

> Are you confident that it's safe to move the pci_dev_put(), so it is
> released before configuring the bridge?

I'm confident that I'm not changing the lifetime assumptions in
acpiphp_configure_bridge(), as the old code didn't seem to care
either.

Commit d6aa484c (acpiphp: convert to acpi_get_pci_dev) changed
from pci_find_bus() to use acpi_get_pci_dev(), and pci_find_bus()
does not elevate any reference counts.

What I'm trying to fix here is that acpi_get_pci_dev() /might/
not work all the time, namely on machines that have both:

	a) hotpluggable root bridges
	b) non-materialized root bridges

> What do you think about something like this (even though the get/put
> is still a little clunky):
> 
> 	struct pci_dev *dev = NULL;
> 
> 	root = acpi_pci_find_root(handle);
> 	if (root)
> 		bus = root->bus;
> 	else {
> 		dev = acpi_get_pci_dev(handle);
> 		if (dev)
> 			bus = pdev->subordinate;
> 		else {
> 			err("cannot get PCI domain and bus number for bridge\n");
> 			return -EINVAL;
> 		}
> 	}
> 
> 	pci_bus_size_bridges(bus);
> 	...
> 	if (dev)
> 		pci_dev_put(dev);
> 	return 0;
 
This seems like a good approach too, but I'd like to understand
your concern about acpi_is_root_bridge() first.

Thanks for the review.

/ac

Re: [PATCH v2 2/2] PCI Hotplug: acpiphp: get pci_bus from acpi handle correctly

[Bjorn Helgaas]

On Tuesday 21 July 2009 01:57:55 pm Alex Chiang wrote:
> * Bjorn Helgaas <bjorn.helgaas@hp.com>:
> > On Tuesday 14 July 2009 02:53:33 pm Alex Chiang wrote:
> > > We cannot simply call acpi_get_pci_dev() on any random ACPI handle
> > > and hope that it works, because a PCI root bridge may not have
> > > an associated struct pci_dev.
> > > 
> > > This is allowed per the PCI specification, and is referred to as a
> > > non-materialized bridge.
> > > 
> > > So, depending on the type of PCI bridge that the handle points to,
> > > use the appropriate interface to return the struct pci_bus correctly.
> > > 
> > > Signed-off-by: Alex Chiang <achiang@hp.com>
> > > ---
> > > 
> > >  drivers/pci/hotplug/acpiphp_glue.c |   27 ++++++++++++++++-----------
> > >  1 files changed, 16 insertions(+), 11 deletions(-)
> > > 
> > > diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
> > > index 0cb0f83..fa4658b 100644
> > > --- a/drivers/pci/hotplug/acpiphp_glue.c
> > > +++ b/drivers/pci/hotplug/acpiphp_glue.c
> > > @@ -62,6 +62,21 @@ static void acpiphp_sanitize_bus(struct pci_bus *bus);
> > >  static void acpiphp_set_hpp_values(acpi_handle handle, struct pci_bus *bus);
> > >  static void handle_hotplug_event_func(acpi_handle handle, u32 type, void *context);
> > >  
> > > +static struct pci_bus *pci_bus_from_handle(acpi_handle handle)
> > > +{
> > > +	struct pci_bus *pbus;
> > > +
> > > +	if (acpi_is_root_bridge(handle)) {
> > > +		struct acpi_pci_root *root = acpi_pci_find_root(handle);
> > > +		pbus = root->bus;
> > > +	} else {
> > > +		struct pci_dev *pdev = acpi_get_pci_dev(handle);
> > > +		pbus = pdev->subordinate;
> > > +		pci_dev_put(pdev);
> > > +	}
> > > +	return pbus;
> > 
> > I worry that acpi_is_root_bridge() merely checks the device IDs of
> > "handle", which isn't quite the same as checking whether the pci_root
> > driver has claimed "handle".
> 
> Hm, I understand this concern in a theoretical sense, but could
> you explain more of what you're thinking about, and give me a
> concrete example of something that might go wrong here?

My concern is only theoretical -- I could imagine a PNP0A03 device
in the namespace (so acpi_is_root_bridge() is true) that has not been
claimed by the pci_root driver (so acpi_pci_find_root() returns NULL).

I don't think this will happen in practice because pci_root can't be
a module, but it's easier to analyze with just one check, since you
can learn everything you need from acpi_pci_find_root() without also
depending on acpi_is_root_bridge().

Bjorn

Re: [PATCH v2 2/2] PCI Hotplug: acpiphp: get pci_bus from acpi handle correctly

[Alex Chiang]

* Bjorn Helgaas <bjorn.helgaas@hp.com>:
> On Tuesday 21 July 2009 01:57:55 pm Alex Chiang wrote:
> > * Bjorn Helgaas <bjorn.helgaas@hp.com>:
> > > On Tuesday 14 July 2009 02:53:33 pm Alex Chiang wrote:
> > > > +static struct pci_bus *pci_bus_from_handle(acpi_handle handle)
> > > > +{
> > > > +	struct pci_bus *pbus;
> > > > +
> > > > +	if (acpi_is_root_bridge(handle)) {
> > > > +		struct acpi_pci_root *root = acpi_pci_find_root(handle);
> > > > +		pbus = root->bus;
> > > > +	} else {
> > > > +		struct pci_dev *pdev = acpi_get_pci_dev(handle);
> > > > +		pbus = pdev->subordinate;
> > > > +		pci_dev_put(pdev);
> > > > +	}
> > > > +	return pbus;
> > > 
> > > I worry that acpi_is_root_bridge() merely checks the device IDs of
> > > "handle", which isn't quite the same as checking whether the pci_root
> > > driver has claimed "handle".
> > 
> > Hm, I understand this concern in a theoretical sense, but could
> > you explain more of what you're thinking about, and give me a
> > concrete example of something that might go wrong here?
> 
> My concern is only theoretical -- I could imagine a PNP0A03 device
> in the namespace (so acpi_is_root_bridge() is true) that has not been
> claimed by the pci_root driver (so acpi_pci_find_root() returns NULL).
> 
> I don't think this will happen in practice because pci_root can't be
> a module, but it's easier to analyze with just one check, since you
> can learn everything you need from acpi_pci_find_root() without also
> depending on acpi_is_root_bridge().

Ah, that makes sense.

I can respin one more time using your suggestion (although I'll
probably keep it factored out into a separate function).

Thanks.

/ac