PCI: hotplug: Drop hotplug_slot_info

Ever since the PCI hotplug core was introduced in 2002, drivers had to
allocate and register a struct hotplug_slot_info for every slot:
https://git.kernel.org/tglx/history/c/a8a2069f432c

Apparently the idea was that drivers furnish the hotplug core with an
up-to-date card presence status, power status, latch status and
attention indicator status as well as notify the hotplug core of changes
thereof.  However only 4 out of 12 hotplug drivers bother to notify the
hotplug core with pci_hp_change_slot_info() and the hotplug core never
made any use of the information:  There is just a single macro in
pci_hotplug_core.c, GET_STATUS(), which uses the hotplug_slot_info if
the driver lacks the corresponding callback in hotplug_slot_ops.  The
macro is called when the user reads the attribute via sysfs.

Now, if the callback isn't defined, the attribute isn't exposed in sysfs
in the first place (see e.g. has_power_file()).  There are only two
situations when the hotplug_slot_info would actually be accessed:

* If the driver defines ->enable_slot or ->disable_slot but not
  ->get_power_status.

* If the driver defines ->set_attention_status but not
  ->get_attention_status.

There is no driver doing the former and just a single driver doing the
latter, namely pnv_php.c.  Amend it with a ->get_attention_status
callback.  With that, the hotplug_slot_info becomes completely unused by
the PCI hotplug core.  But a few drivers use it internally as a cache:

cpcihp uses it to cache the latch_status and adapter_status.
cpqhp uses it to cache the adapter_status.
pnv_php and rpaphp use it to cache the attention_status.
shpchp uses it to cache all four values.

Amend these drivers to cache the information in their private slot
struct.  shpchp's slot struct already contains members to cache the
power_status and adapter_status, so additional members are only needed
for the other two values.  In the case of cpqphp, the cached value is
only accessed in a single place, so instead of caching it, read the
current value from the hardware.

Caution:  acpiphp, cpci, cpqhp, shpchp, asus-wmi and eeepc-laptop
populate the hotplug_slot_info with initial values on probe.  That code
is herewith removed.  There is a theoretical chance that the code has
side effects without which the driver fails to function, e.g. if the
ACPI method to read the adapter status needs to be executed at least
once on probe.  That seems unlikely to me, still maintainers should
review the changes carefully for this possibility.

Rafael adds: "I'm not aware of any case in which it will break anything,
[...] but if that happens, it may be necessary to add the execution of
the control methods in question directly to the initialization part."

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Tyrel Datwyler <tyreld@linux.vnet.ibm.com>  # drivers/pci/hotplug/rpa*
Acked-by: Sebastian Ott <sebott@linux.ibm.com>        # drivers/pci/hotplug/s390*
Acked-by: Andy Shevchenko <andy.shevchenko@gmail.com> # drivers/platform/x86
Cc: Len Brown <lenb@kernel.org>
Cc: Scott Murray <scott@spiteful.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Oliver OHalloran <oliveroh@au1.ibm.com>
Cc: Gavin Shan <gwshan@linux.vnet.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Cc: Corentin Chary <corentin.chary@gmail.com>
Cc: Darren Hart <dvhart@infradead.org>

1 files changed, 0 insertions, 30 deletions

diff --git a/include/linux/pci_hotplug.h b/include/linux/pci_hotplug.h
index 372dbe95c207..6f07a4e1de8d 100644
--- a/include/linux/pci_hotplug.h
+++ b/include/linux/pci_hotplug.h
@@ -23,17 +23,9 @@
  * @hardware_test: Called to run a specified hardware test on the specified
  * slot.
  * @get_power_status: Called to get the current power status of a slot.
- *	If this field is NULL, the value passed in the struct hotplug_slot_info
- *	will be used when this value is requested by a user.
  * @get_attention_status: Called to get the current attention status of a slot.
- *	If this field is NULL, the value passed in the struct hotplug_slot_info
- *	will be used when this value is requested by a user.
  * @get_latch_status: Called to get the current latch status of a slot.
- *	If this field is NULL, the value passed in the struct hotplug_slot_info
- *	will be used when this value is requested by a user.
  * @get_adapter_status: Called to get see if an adapter is present in the slot or not.
- *	If this field is NULL, the value passed in the struct hotplug_slot_info
- *	will be used when this value is requested by a user.
  * @reset_slot: Optional interface to allow override of a bus reset for the
  *	slot for cases where a secondary bus reset can result in spurious
  *	hotplug events or where a slot can be reset independent of the bus.
@@ -56,26 +48,8 @@ struct hotplug_slot_ops {
 };
 
 /**
- * struct hotplug_slot_info - used to notify the hotplug pci core of the state of the slot
- * @power_status: if power is enabled or not (1/0)
- * @attention_status: if the attention light is enabled or not (1/0)
- * @latch_status: if the latch (if any) is open or closed (1/0)
- * @adapter_status: if there is a pci board present in the slot or not (1/0)
- *
- * Used to notify the hotplug pci core of the status of a specific slot.
- */
-struct hotplug_slot_info {
-	u8	power_status;
-	u8	attention_status;
-	u8	latch_status;
-	u8	adapter_status;
-};
-
-/**
  * struct hotplug_slot - used to register a physical slot with the hotplug pci core
  * @ops: pointer to the &struct hotplug_slot_ops to be used for this slot
- * @info: pointer to the &struct hotplug_slot_info for the initial values for
- * this slot.
  * @private: used by the hotplug pci controller driver to store whatever it
  * needs.
  * @owner: The module owner of this structure
@@ -83,7 +57,6 @@ struct hotplug_slot_info {
  */
 struct hotplug_slot {
 	const struct hotplug_slot_ops	*ops;
-	struct hotplug_slot_info	*info;
 	void				*private;
 
 	/* Variables below this are for use only by the hotplug pci core. */
@@ -110,9 +83,6 @@ void pci_hp_del(struct hotplug_slot *slot);
 void pci_hp_destroy(struct hotplug_slot *slot);
 void pci_hp_deregister(struct hotplug_slot *slot);
 
-int __must_check pci_hp_change_slot_info(struct hotplug_slot *slot,
-					 struct hotplug_slot_info *info);
-
 /* use a define to avoid include chaining to get THIS_MODULE & friends */
 #define pci_hp_register(slot, pbus, devnr, name) \
 	__pci_hp_register(slot, pbus, devnr, name, THIS_MODULE, KBUILD_MODNAME)