[PATCH] reduce nr of ptr derefs in drivers/pci/hotplug/shpchp_core.c

[Jesper Juhl]

Here's a small patch to reduce the nr. of pointer dereferences in
drivers/pci/hotplug/shpchp_core.c

Benefits:
 - micro speed optimization due to fewer pointer derefs
 - get rid of a pointless cast of kmalloc() return value
 - generated code is slightly smaller
 - better readability

Please consider applying.


Signed-off-by: Jesper Juhl <jesper.juhl@xxxxxxxxx>
---

 drivers/pci/hotplug/shpchp_core.c |   92 +++++++++++++++++++++-----------------
 1 files changed, 52 insertions(+), 40 deletions(-)

orig:
   text    data     bss     dec     hex filename
   5917     448      16    6381    18ed drivers/pci/hotplug/shpchp_core.o
patched:
   text    data     bss     dec     hex filename
   5896     448      16    6360    18d8 drivers/pci/hotplug/shpchp_core.o

--- linux-2.6.15-rc5-git1-orig/drivers/pci/hotplug/shpchp_core.c	2005-12-04 18:48:04.000000000 +0100
+++ linux-2.6.15-rc5-git1/drivers/pci/hotplug/shpchp_core.c	2005-12-11 05:12:04.000000000 +0100
@@ -99,7 +99,10 @@ static void release_slot(struct hotplug_
 
 static int init_slots(struct controller *ctrl)
 {
-	struct slot *new_slot;
+	struct slot *slot;
+	struct hpc_ops *hpc_ops;
+	struct hotplug_slot *hotplug_slot;
+	struct hotplug_slot_info *hotplug_slot_info;
 	u8 number_of_slots;
 	u8 slot_device;
 	u32 slot_number, sun;
@@ -110,58 +113,68 @@ static int init_slots(struct controller 
 	slot_number = ctrl->first_slot;
 
 	while (number_of_slots) {
-		new_slot = (struct slot *) kmalloc(sizeof(struct slot), GFP_KERNEL);
-		if (!new_slot)
+		slot = kmalloc(sizeof(struct slot), GFP_KERNEL);
+		if (!slot)
 			goto error;
 
-		memset(new_slot, 0, sizeof(struct slot));
-		new_slot->hotplug_slot = kmalloc (sizeof (struct hotplug_slot), GFP_KERNEL);
-		if (!new_slot->hotplug_slot)
+		memset(slot, 0, sizeof(struct slot));
+		slot->hotplug_slot =
+			kmalloc(sizeof(struct hotplug_slot), GFP_KERNEL);
+		if (!slot->hotplug_slot)
 			goto error_slot;
-		memset(new_slot->hotplug_slot, 0, sizeof (struct hotplug_slot));
+		hotplug_slot = slot->hotplug_slot;
+		memset(hotplug_slot, 0, sizeof(struct hotplug_slot));
 
-		new_slot->hotplug_slot->info = kmalloc (sizeof (struct hotplug_slot_info), GFP_KERNEL);
-		if (!new_slot->hotplug_slot->info)
+		hotplug_slot->info =
+			kmalloc(sizeof(struct hotplug_slot_info), GFP_KERNEL);
+		if (!hotplug_slot->info)
 			goto error_hpslot;
-		memset(new_slot->hotplug_slot->info, 0, sizeof (struct hotplug_slot_info));
-		new_slot->hotplug_slot->name = kmalloc (SLOT_NAME_SIZE, GFP_KERNEL);
-		if (!new_slot->hotplug_slot->name)
+		hotplug_slot_info = hotplug_slot->info;
+		memset(hotplug_slot_info, 0, sizeof(struct hotplug_slot_info));
+		hotplug_slot->name = kmalloc(SLOT_NAME_SIZE, GFP_KERNEL);
+		if (!hotplug_slot->name)
 			goto error_info;
 
-		new_slot->magic = SLOT_MAGIC;
-		new_slot->ctrl = ctrl;
-		new_slot->bus = ctrl->slot_bus;
-		new_slot->device = slot_device;
-		new_slot->hpc_ops = ctrl->hpc_ops;
+		slot->magic = SLOT_MAGIC;
+		slot->ctrl = ctrl;
+		slot->bus = ctrl->slot_bus;
+		slot->device = slot_device;
+		slot->hpc_ops = hpc_ops = ctrl->hpc_ops;
 
 		if (shpchprm_get_physical_slot_number(ctrl, &sun,
-					new_slot->bus, new_slot->device))
+					slot->bus, slot->device))
 			goto error_name;
 
-		new_slot->number = sun;
-		new_slot->hp_slot = slot_device - ctrl->slot_device_offset;
+		slot->number = sun;
+		slot->hp_slot = slot_device - ctrl->slot_device_offset;
 
 		/* register this slot with the hotplug pci core */
-		new_slot->hotplug_slot->private = new_slot;
-		new_slot->hotplug_slot->release = &release_slot;
-		make_slot_name(new_slot->hotplug_slot->name, SLOT_NAME_SIZE, new_slot);
-		new_slot->hotplug_slot->ops = &shpchp_hotplug_slot_ops;
-
-		new_slot->hpc_ops->get_power_status(new_slot, &(new_slot->hotplug_slot->info->power_status));
-		new_slot->hpc_ops->get_attention_status(new_slot, &(new_slot->hotplug_slot->info->attention_status));
-		new_slot->hpc_ops->get_latch_status(new_slot, &(new_slot->hotplug_slot->info->latch_status));
-		new_slot->hpc_ops->get_adapter_status(new_slot, &(new_slot->hotplug_slot->info->adapter_status));
-
-		dbg("Registering bus=%x dev=%x hp_slot=%x sun=%x slot_device_offset=%x\n", new_slot->bus, 
-			new_slot->device, new_slot->hp_slot, new_slot->number, ctrl->slot_device_offset);
-		result = pci_hp_register (new_slot->hotplug_slot);
+		hotplug_slot->private = slot;
+		hotplug_slot->release = &release_slot;
+		make_slot_name(hotplug_slot->name, SLOT_NAME_SIZE, slot);
+		hotplug_slot->ops = &shpchp_hotplug_slot_ops;
+
+		hpc_ops->get_power_status(slot,
+			&(hotplug_slot_info->power_status));
+		hpc_ops->get_attention_status(slot,
+			&(hotplug_slot_info->attention_status));
+		hpc_ops->get_latch_status(slot,
+			&(hotplug_slot_info->latch_status));
+		hpc_ops->get_adapter_status(slot,
+			&(hotplug_slot_info->adapter_status));
+
+		dbg("Registering bus=%x dev=%x hp_slot=%x sun=%x "
+			"slot_device_offset=%x\n",
+			slot->bus, slot->device, slot->hp_slot, slot->number,
+			ctrl->slot_device_offset);
+		result = pci_hp_register(hotplug_slot);
 		if (result) {
 			err ("pci_hp_register failed with error %d\n", result);
 			goto error_name;
 		}
 
-		new_slot->next = ctrl->slot;
-		ctrl->slot = new_slot;
+		slot->next = ctrl->slot;
+		ctrl->slot = slot;
 
 		number_of_slots--;
 		slot_device++;
@@ -169,15 +182,14 @@ static int init_slots(struct controller 
 	}
 
 	return 0;
-
 error_name:
-	kfree(new_slot->hotplug_slot->name);
+	kfree(hotplug_slot->name);
 error_info:
-	kfree(new_slot->hotplug_slot->info);
+	kfree(hotplug_slot_info);
 error_hpslot:
-	kfree(new_slot->hotplug_slot);
+	kfree(hotplug_slot);
 error_slot:
-	kfree(new_slot);
+	kfree(slot);
 error:
 	return result;
 }



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