From 4186391b43bf101fda08e92185359c94812e2c3d Mon Sep 17 00:00:00 2001
From: Martin Mares <mj@ucw.cz>
Date: Sat, 14 May 2016 11:57:01 +0200
Subject: [PATCH] Domains: Legacy 16-bit domain numbers are maintained in
 generic code

Previously, backward compatibility was kept only with the sysfs
back-end.

Also, domains which do not fit in 16 bits are replaced by 0xffff.
---
 lib/access.c | 12 ++++++++++++
 lib/pci.h    |  5 +++--
 lib/sysfs.c  | 10 +---------
 3 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/lib/access.c b/lib/access.c
index 17b8bed..d991129 100644
--- a/lib/access.c
+++ b/lib/access.c
@@ -40,6 +40,18 @@ pci_link_dev(struct pci_access *a, struct pci_dev *d)
   d->next = a->devices;
   a->devices = d;
 
+  /*
+   * Applications compiled with older versions of libpci do not expect
+   * 32-bit domain numbers. To keep them working, we keep a 16-bit
+   * version of the domain number at the previous location in struct
+   * pci_dev. This will keep backward compatibility on systems which
+   * don't require large domain numbers.
+   */
+  if (d->domain > 0xffff)
+    d->domain_16 = 0xffff;
+  else
+    d->domain_16 = d->domain;
+
   return 1;
 }
 
diff --git a/lib/pci.h b/lib/pci.h
index 47610f3..e3175a3 100644
--- a/lib/pci.h
+++ b/lib/pci.h
@@ -119,7 +119,8 @@ struct pci_param *pci_walk_params(struct pci_access *acc, struct pci_param *prev
 
 struct pci_dev {
   struct pci_dev *next;			/* Next device in the chain */
-  u16 domain_16;			/* 16-bit PCI domain (host bridge) */
+  u16 domain_16;			/* 16-bit version of the PCI domain for backward compatibility */
+					/* 0xffff if the real domain doesn't fit in 16 bits */
   u8 bus, dev, func;			/* Bus inside domain, device and function */
 
   /* These fields are set by pci_fill_info() */
@@ -138,7 +139,7 @@ struct pci_dev {
   int numa_node;			/* NUMA node */
   pciaddr_t flags[6];			/* PCI_IORESOURCE_* flags for regions */
   pciaddr_t rom_flags;			/* PCI_IORESOURCE_* flags for expansion ROM */
-  int domain;				/* 32-bit PCI domain (host bridge) */
+  int domain;				/* PCI domain (host bridge) */
 
   /* Fields used internally: */
   struct pci_access *access;
diff --git a/lib/sysfs.c b/lib/sysfs.c
index 877310c..5779824 100644
--- a/lib/sysfs.c
+++ b/lib/sysfs.c
@@ -199,16 +199,8 @@ static void sysfs_scan(struct pci_access *a)
 
       /* Ensure kernel provided domain that fits in a signed integer */
       if (dom > 0x7fffffff)
-	a->error("sysfs_scan: invalid domain:%x", dom);
+	a->error("sysfs_scan: Invalid domain %x", dom);
 
-      /*
-       * The domain value is truncated to 16 bits and stored in the pci_dev
-       * structure's legacy 16-bit domain offset for compatibility with
-       * applications compiled with libpci pre-32 bit domains. Such
-       * applications may not work as expected if they are on a machine
-       * utilizing PCI domain numbers requiring more than 16 bits.
-       */
-      d->domain_16 = dom;
       d->domain = dom;
       d->bus = bus;
       d->dev = dev;
-- 
2.39.2