PCI: create function symlinks in /sys/bus/pci/slots/N/

Create convenience symlinks in sysfs, linking slots to device
functions, and vice versa. These links make it easier for users to
figure out which devices actually live in what slots.

For example:

sapphire:/sys/bus/pci/slots # ls
1  10  2  3  4  5  6  7  8  9

sapphire:/sys/bus/pci/slots # ls -l 3
total 0
-r--r--r-- 1 root root 65536 Aug 18 14:10 address
lrwxrwxrwx 1 root root     0 Aug 18 14:10 function0 ->
../../../../devices/pci0000:23/0000:23:01.0
lrwxrwxrwx 1 root root     0 Aug 18 14:10 function1 ->
../../../../devices/pci0000:23/0000:23:01.1

sapphire:/sys/bus/pci/slots # ls -l 3/function0/slot
lrwxrwxrwx 1 root root 0 Aug 18 14:13 3/function0/slot ->
../../../bus/pci/slots/3

The original form of this patch was written by Matthew Wilcox,
and was enhanced to include links from the sysfs slots/ directory
pointing back at the device functions.

Cc: willy@linux.intel.com
Signed-off-by: Alex Chiang <achiang@hp.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

2 files changed, 85 insertions, 0 deletions

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index fad93983bfed..941e939d1da9 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -1011,6 +1011,39 @@ error:
         return retval;
 }
 
+static void pci_remove_slot_links(struct pci_dev *dev)
+{
+        char func[10];
+        struct pci_slot *slot;
+
+        sysfs_remove_link(&dev->dev.kobj, "slot");
+        list_for_each_entry(slot, &dev->bus->slots, list) {
+                if (slot->number != PCI_SLOT(dev->devfn))
+                        continue;
+                snprintf(func, 10, "function%d", PCI_FUNC(dev->devfn));
+                sysfs_remove_link(&slot->kobj, func);
+        }
+}
+
+static int pci_create_slot_links(struct pci_dev *dev)
+{
+        int result = 0;
+        char func[10];
+        struct pci_slot *slot;
+
+        list_for_each_entry(slot, &dev->bus->slots, list) {
+                if (slot->number != PCI_SLOT(dev->devfn))
+                        continue;
+                result = sysfs_create_link(&dev->dev.kobj, &slot->kobj, "slot");
+                if (result)
+                        goto out;
+                snprintf(func, 10, "function%d", PCI_FUNC(dev->devfn));
+                result = sysfs_create_link(&slot->kobj, &dev->dev.kobj, func);
+        }
+out:
+        return result;
+}
+
 int __must_check pci_create_sysfs_dev_files (struct pci_dev *pdev)
 {
         int retval;
@@ -1073,6 +1106,8 @@ int __must_check pci_create_sysfs_dev_files (struct pci_dev *pdev)
         if (retval)
                 goto err_vga_file;
 
+        pci_create_slot_links(pdev);
+
         return 0;
 
 err_vga_file:
@@ -1122,6 +1157,8 @@ void pci_remove_sysfs_dev_files(struct pci_dev *pdev)
         if (!sysfs_initialized)
                 return;
 
+        pci_remove_slot_links(pdev);
+
         pci_remove_capabilities_sysfs(pdev);
 
         if (pdev->cfg_size < PCI_CFG_SPACE_EXP_SIZE)
diff --git a/drivers/pci/slot.c b/drivers/pci/slot.c
index 659eaa0fc48f..e0189cf7c558 100644
--- a/drivers/pci/slot.c
+++ b/drivers/pci/slot.c
@@ -97,6 +97,50 @@ static ssize_t cur_speed_read_file(struct pci_slot *slot, char *buf)
         return bus_speed_read(slot->bus->cur_bus_speed, buf);
 }
 
+static void remove_sysfs_files(struct pci_slot *slot)
+{
+        char func[10];
+        struct list_head *tmp;
+
+        list_for_each(tmp, &slot->bus->devices) {
+                struct pci_dev *dev = pci_dev_b(tmp);
+                if (PCI_SLOT(dev->devfn) != slot->number)
+                        continue;
+                sysfs_remove_link(&dev->dev.kobj, "slot");
+
+                snprintf(func, 10, "function%d", PCI_FUNC(dev->devfn));
+                sysfs_remove_link(&slot->kobj, func);
+        }
+}
+
+static int create_sysfs_files(struct pci_slot *slot)
+{
+        int result;
+        char func[10];
+        struct list_head *tmp;
+
+        list_for_each(tmp, &slot->bus->devices) {
+                struct pci_dev *dev = pci_dev_b(tmp);
+                if (PCI_SLOT(dev->devfn) != slot->number)
+                        continue;
+
+                result = sysfs_create_link(&dev->dev.kobj, &slot->kobj, "slot");
+                if (result)
+                        goto fail;
+
+                snprintf(func, 10, "function%d", PCI_FUNC(dev->devfn));
+                result = sysfs_create_link(&slot->kobj, &dev->dev.kobj, func);
+                if (result)
+                        goto fail;
+        }
+
+        return 0;
+
+fail:
+        remove_sysfs_files(slot);
+        return result;
+}
+
 static void pci_slot_release(struct kobject *kobj)
 {
         struct pci_dev *dev;
@@ -109,6 +153,8 @@ static void pci_slot_release(struct kobject *kobj)
                 if (PCI_SLOT(dev->devfn) == slot->number)
                         dev->slot = NULL;
 
+        remove_sysfs_files(slot);
+
         list_del(&slot->list);
 
         kfree(slot);
@@ -300,6 +346,8 @@ placeholder:
         INIT_LIST_HEAD(&slot->list);
         list_add(&slot->list, &parent->slots);
 
+        create_sysfs_files(slot);
+
         list_for_each_entry(dev, &parent->devices, bus_list)
                 if (PCI_SLOT(dev->devfn) == slot_nr)
                         dev->slot = slot;