linux-kernel - [PATCH 1/3] PCI: Add support in pci_walk_bus() to invoke callback matching RID

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Date:   Mon, 20 Sep 2021 12:11:31 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>
CC:     <linux-kernel@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Kishon Vijay Abraham I <kishon@...com>,
        <lokeshvutla@...com>
Subject: [PATCH 1/3] PCI: Add support in pci_walk_bus() to invoke callback matching RID

Add two arguments to pci_walk_bus() [requestorID and mask], and add
support in pci_walk_bus() to invoke the *callback* only for devices
whose RequestorID after applying *mask* matches with *requestorID*
passed as argument.

This is done in preparation for calculating the total number of
interrupt vectors that has to be supported by a specific GIC ITS device ID,
specifically when "msi-map-mask" is populated in device tree.

Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
---
 drivers/pci/bus.c   | 13 +++++++++----
 include/linux/pci.h |  7 +++++--
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index 3cef835b375f..e381e639ceaa 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -358,10 +358,12 @@ void pci_bus_add_devices(const struct pci_bus *bus)
 }
 EXPORT_SYMBOL(pci_bus_add_devices);
 
-/** pci_walk_bus - walk devices on/under bus, calling callback.
+/** __pci_walk_bus - walk devices on/under bus matching requestor ID, calling callback.
  *  @top      bus whose devices should be walked
  *  @cb       callback to be called for each device found
  *  @userdata arbitrary pointer to be passed to callback.
+ *  @rid      Requestor ID that has to be matched for the callback to be invoked
+ *  @mask     Mask that has to be applied to pci_dev_id(), before compating it with @rid
  *
  *  Walk the given bus, including any bridged devices
  *  on buses under this bus.  Call the provided callback
@@ -371,8 +373,8 @@ EXPORT_SYMBOL(pci_bus_add_devices);
  *  other than 0, we break out.
  *
  */
-void pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *),
-		  void *userdata)
+void __pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *),
+		    void *userdata, u32 rid, u32 mask)
 {
 	struct pci_dev *dev;
 	struct pci_bus *bus;
@@ -399,13 +401,16 @@ void pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *),
 		} else
 			next = dev->bus_list.next;
 
+		if (mask != 0xffff && ((pci_dev_id(dev) & mask) != rid))
+			continue;
+
 		retval = cb(dev, userdata);
 		if (retval)
 			break;
 	}
 	up_read(&pci_bus_sem);
 }
-EXPORT_SYMBOL_GPL(pci_walk_bus);
+EXPORT_SYMBOL_GPL(__pci_walk_bus);
 
 struct pci_bus *pci_bus_get(struct pci_bus *bus)
 {
diff --git a/include/linux/pci.h b/include/linux/pci.h
index cd8aa6fce204..8500fec56e50 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1473,14 +1473,17 @@ const struct pci_device_id *pci_match_id(const struct pci_device_id *ids,
 int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max,
 		    int pass);
 
-void pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *),
-		  void *userdata);
+void __pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *),
+		    void *userdata, u32 rid, u32 mask);
 int pci_cfg_space_size(struct pci_dev *dev);
 unsigned char pci_bus_max_busnr(struct pci_bus *bus);
 void pci_setup_bridge(struct pci_bus *bus);
 resource_size_t pcibios_window_alignment(struct pci_bus *bus,
 					 unsigned long type);
 
+#define pci_walk_bus(top, cb, userdata) \
+	 __pci_walk_bus((top), (cb), (userdata), 0x0, 0xffff)
+
 #define PCI_VGA_STATE_CHANGE_BRIDGE (1 << 0)
 #define PCI_VGA_STATE_CHANGE_DECODES (1 << 1)
 
-- 
2.17.1