[RFC][PATCH 25/30] ACPI / hotplug / PCI: Allow slots without new devices to be rescanned

From: Rafael J. Wysocki
Date: Thu Jul 11 2013 - 20:06:21 EST


From: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>

Currently, enable_device() checks the return value of pci_scan_slot()
and returns immediately if that's 0 (meaning that no new functions
have been found in the slot). However, if one of the functions in
the slot is a bridge, some new devices may appear below it even if
the bridge itself is present continuously, so it generally is
necessary to do the rescan anyway just in case. [In particular,
that's necessary with the Thunderbolt daisy chaining in which case
new devices may be connected to the existing ones down the chain.]

The correctness of this change relies on the ability of
pcibios_resource_survey_bus() to detect if it has already been called
for the given bus and to skip it if so. Failure to do that will lead
to resource allocation conflicts.

[rjw: Changelog]
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
---
drivers/pci/hotplug/acpiphp_glue.c | 11 ++---------
drivers/pci/hotplug/acpiphp_glue.c | 11 ++---------
1 file changed, 2 insertions(+), 9 deletions(-)

Index: linux-pm/drivers/pci/hotplug/acpiphp_glue.c
===================================================================
--- linux-pm.orig/drivers/pci/hotplug/acpiphp_glue.c
+++ linux-pm/drivers/pci/hotplug/acpiphp_glue.c
@@ -554,18 +554,13 @@ static int __ref enable_device(struct ac
struct pci_dev *dev;
struct pci_bus *bus = slot->bus;
struct acpiphp_func *func;
- int num, max, pass;
+ int max, pass;
LIST_HEAD(add_list);

list_for_each_entry(func, &slot->funcs, sibling)
acpiphp_bus_add(func_to_handle(func));

- num = pci_scan_slot(bus, PCI_DEVFN(slot->device, 0));
- if (num == 0) {
- /* Maybe only part of funcs are added. */
- dbg("No new device found\n");
- goto err_exit;
- }
+ pci_scan_slot(bus, PCI_DEVFN(slot->device, 0));

max = acpiphp_max_busnr(bus);
for (pass = 0; pass < 2; pass++) {
@@ -611,8 +606,6 @@ static int __ref enable_device(struct ac
}
}

-
- err_exit:
return 0;
}


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