From 125450f814418b9f889c9885831467d1b2e25a7d Mon Sep 17 00:00:00 2001 From: Lukas Wunner Date: Sat, 8 Sep 2018 09:59:01 +0200 Subject: PCI: hotplug: Embed hotplug_slot When the PCI hotplug core and its first user, cpqphp, were introduced in February 2002 with historic commit a8a2069f432c, cpqphp allocated a slot struct for its internal use plus a hotplug_slot struct to be registered with the hotplug core and linked the two with pointers: https://git.kernel.org/tglx/history/c/a8a2069f432c Nowadays, the predominant pattern in the tree is to embed ("subclass") such structures in one another and cast to the containing struct with container_of(). But it wasn't until July 2002 that container_of() was introduced with historic commit ec4f214232cf: https://git.kernel.org/tglx/history/c/ec4f214232cf pnv_php, introduced in 2016, did the right thing and embedded struct hotplug_slot in its internal struct pnv_php_slot, but all other drivers cargo-culted cpqphp's design and linked separate structs with pointers. Embedding structs is preferrable to linking them with pointers because it requires fewer allocations, thereby reducing overhead and simplifying error paths. Casting an embedded struct to the containing struct becomes a cheap subtraction rather than a dereference. And having fewer pointers reduces the risk of them pointing nowhere either accidentally or due to an attack. Convert all drivers to embed struct hotplug_slot in their internal slot struct. The "private" pointer in struct hotplug_slot thereby becomes unused, so drop it. Signed-off-by: Lukas Wunner Signed-off-by: Bjorn Helgaas Reviewed-by: Rafael J. Wysocki Acked-by: Tyrel Datwyler # drivers/pci/hotplug/rpa* Acked-by: Sebastian Ott # drivers/pci/hotplug/s390* Acked-by: Andy Shevchenko # drivers/platform/x86 Cc: Len Brown Cc: Scott Murray Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Michael Ellerman Cc: Oliver OHalloran Cc: Gavin Shan Cc: Gerald Schaefer Cc: Corentin Chary Cc: Darren Hart --- drivers/pci/hotplug/acpiphp_ibm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/pci/hotplug/acpiphp_ibm.c') diff --git a/drivers/pci/hotplug/acpiphp_ibm.c b/drivers/pci/hotplug/acpiphp_ibm.c index 41713f16ff97..df48b3b03ab4 100644 --- a/drivers/pci/hotplug/acpiphp_ibm.c +++ b/drivers/pci/hotplug/acpiphp_ibm.c @@ -41,7 +41,7 @@ MODULE_VERSION(DRIVER_VERSION); #define IBM_HARDWARE_ID1 "IBM37D0" #define IBM_HARDWARE_ID2 "IBM37D4" -#define hpslot_to_sun(A) (((struct slot *)((A)->private))->sun) +#define hpslot_to_sun(A) (to_slot(A)->sun) /* union apci_descriptor - allows access to the * various device descriptors that are embedded in the -- cgit v1.2.3