linux-kernel - [PATCH 1/2] gpio / ACPI: Avoid unnecessary checks in __gpiod_get

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Date:	Tue, 10 Mar 2015 23:08:57 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	Alexandre Courbot <gnurou@...il.com>, linux-gpio@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: [PATCH 1/2] gpio / ACPI: Avoid unnecessary checks in __gpiod_get_index()

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

If dev is NULL in __gpiod_get_index() and both ACPI and OF are
enabled, it will be checked twice before the code decides to give
up with DT/ACPI lookup, so avoid that.

Also use the observation that ACPI_COMPANION() is much more efficient
than ACPI_HANDLE(), because the latter uses the former and carries out
a check and a pointer dereference on top of it, so replace the
ACPI_HANDLE() check with an ACPI_COMPANION() one which does not
require the additional IS_ENABLED(CONFIG_ACPI) check too.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/gpio/gpiolib.c |   16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

Index: linux-pm/drivers/gpio/gpiolib.c
===================================================================
--- linux-pm.orig/drivers/gpio/gpiolib.c
+++ linux-pm/drivers/gpio/gpiolib.c
@@ -1865,13 +1865,15 @@ struct gpio_desc *__must_check __gpiod_g
 
 	dev_dbg(dev, "GPIO lookup for consumer %s\n", con_id);
 
-	/* Using device tree? */
-	if (IS_ENABLED(CONFIG_OF) && dev && dev->of_node) {
-		dev_dbg(dev, "using device tree for GPIO lookup\n");
-		desc = of_find_gpio(dev, con_id, idx, &lookupflags);
-	} else if (IS_ENABLED(CONFIG_ACPI) && dev && ACPI_HANDLE(dev)) {
-		dev_dbg(dev, "using ACPI for GPIO lookup\n");
-		desc = acpi_find_gpio(dev, con_id, idx, &lookupflags);
+	if (dev) {
+		/* Using device tree? */
+		if (IS_ENABLED(CONFIG_OF) && dev->of_node) {
+			dev_dbg(dev, "using device tree for GPIO lookup\n");
+			desc = of_find_gpio(dev, con_id, idx, &lookupflags);
+		} else if (ACPI_COMPANION(dev)) {
+			dev_dbg(dev, "using ACPI for GPIO lookup\n");
+			desc = acpi_find_gpio(dev, con_id, idx, &lookupflags);
+		}
 	}
 
 	/*

--
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