Now we have pci_root_buses list, and there is lots of iteration with
list_of_each of it, that is not safe after we add pci root bus hotplug
support after booting stage.

Also pci_find_next_bus is pretty misleading name, and it is only finding
next root bus instead of regular pci bus.

Add pci_get_next_host_bridge and use bus_find_device in driver core to
iterate host bridge and the same time get root bus.

In folllowing patches will replace searching root bus with searching 
host_bridge.
after using with that host-bridge, will need to call put device to release
reference if break early from the loop.

After those replacing, we even could kill pci_root_buses list.

-v2: fixes compiling error when CONFIG_PCI is not defined that Fengguang Wu 
found.

Signed-off-by: Yinghai Lu <ying...@kernel.org>
Cc: Mauro Carvalho Chehab <mche...@redhat.com>
Cc: Doug Thompson <dougthomp...@xmission.com>
Cc: linux-e...@vger.kernel.org
Cc: x...@kernel.org
Cc: David Airlie <airl...@linux.ie>
Cc: dri-de...@lists.freedesktop.org
Cc: "David S. Miller" <da...@davemloft.net>
Cc: sparcli...@vger.kernel.org
Cc: Tony Luck <tony.l...@intel.com>
Cc: Fenghua Yu <fenghua...@intel.com>
Cc: linux-i...@vger.kernel.org
Cc: linux-al...@sgi.com
Cc: Richard Henderson <r...@twiddle.net>
Cc: Ivan Kokshaysky <i...@jurassic.park.msu.ru>
Cc: Matt Turner <matts...@gmail.com>
Cc: linux-al...@vger.kernel.org
Cc: Russell King <li...@arm.linux.org.uk>
Cc: linux-arm-ker...@lists.infradead.org
Cc: David Howells <dhowe...@redhat.com>
Cc: Michal Simek <mon...@monstr.eu>
Cc: microblaze-ucli...@itee.uq.edu.au
Cc: Koichi Yasutake <yasutake.koi...@jp.panasonic.com>
Cc: linux-am33-l...@redhat.com
Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org>
Cc: Paul Mackerras <pau...@samba.org>
Cc: linuxppc-dev@lists.ozlabs.org
---
 drivers/pci/search.c |   24 ++++++++++++++++++++++++
 include/linux/pci.h  |    9 +++++++++
 2 files changed, 33 insertions(+)

diff --git a/drivers/pci/search.c b/drivers/pci/search.c
index d0627fa..db0c3a9 100644
--- a/drivers/pci/search.c
+++ b/drivers/pci/search.c
@@ -178,6 +178,30 @@ struct pci_dev *pci_get_domain_bus_and_slot(int domain, 
unsigned int bus,
 }
 EXPORT_SYMBOL(pci_get_domain_bus_and_slot);
 
+static int match_pci_host_bridge(struct device *dev, void *data)
+{
+       return 1;
+}
+
+struct pci_host_bridge *pci_get_next_host_bridge(struct pci_host_bridge *from)
+{
+       struct device *dev;
+       struct device *dev_start = NULL;
+       struct pci_host_bridge *bridge = NULL;
+
+       WARN_ON(in_interrupt());
+       if (from)
+               dev_start = &from->dev;
+       dev = bus_find_device(&pci_host_bridge_bus_type, dev_start, NULL,
+                             match_pci_host_bridge);
+       if (dev)
+               bridge = to_pci_host_bridge(dev);
+       if (from)
+               put_device(&from->dev);
+       return bridge;
+}
+EXPORT_SYMBOL_GPL(pci_get_next_host_bridge);
+
 static int match_pci_dev_by_id(struct device *dev, void *data)
 {
        struct pci_dev *pdev = to_pci_dev(dev);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 9da06ec..67879cb 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -375,6 +375,8 @@ struct pci_host_bridge {
 };
 
 #define        to_pci_host_bridge(n) container_of(n, struct pci_host_bridge, 
dev)
+#define for_each_pci_host_bridge(d) while ((d = pci_get_next_host_bridge(d)) 
!= NULL)
+
 void pci_set_host_bridge_release(struct pci_host_bridge *bridge,
                     void (*release_fn)(struct pci_host_bridge *),
                     void *release_data);
@@ -763,6 +765,7 @@ int pci_find_ht_capability(struct pci_dev *dev, int ht_cap);
 int pci_find_next_ht_capability(struct pci_dev *dev, int pos, int ht_cap);
 struct pci_bus *pci_find_next_bus(const struct pci_bus *from);
 
+struct pci_host_bridge *pci_get_next_host_bridge(struct pci_host_bridge *from);
 struct pci_dev *pci_get_device(unsigned int vendor, unsigned int device,
                                struct pci_dev *from);
 struct pci_dev *pci_get_subsys(unsigned int vendor, unsigned int device,
@@ -1418,6 +1421,12 @@ static inline int pci_domain_nr(struct pci_bus *bus)
 static inline struct pci_dev *pci_dev_get(struct pci_dev *dev)
 { return NULL; }
 
+static inline struct pci_host_bridge *pci_get_next_host_bridge(
+                       struct pci_host_bridge *host_bridge)
+{
+       return NULL;
+}
+
 #define dev_is_pci(d) (false)
 #define dev_is_pf(d) (false)
 #define dev_num_vf(d) (0)
-- 
1.7.10.4

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