linux-kernel - [PATCH] gpiolib: tighten up ACPI legacy gpio lookups

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Message-ID: <20151105193838.GA33410@dtor-ws>
Date:	Thu, 5 Nov 2015 11:38:38 -0800
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	Alexandre Courbot <gnurou@...il.com>,
	Johan Hovold <johan@...nel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	mika.westerberg@...ux.intel.com,
	"Tirdea, Irina" <irina.tirdea@...el.com>,
	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] gpiolib: tighten up ACPI legacy gpio lookups

We should not fall back to the legacy unnamed gpio lookup style if the
driver requests gpios with different names, because we'll give out the same
gpio twice. Let's keep track of the names that were used for the device and
only do the fallback for the first name used.

Also disable fallback to _CRS gpios if ACPI device has DT-like
properties or driver-supplied gpio mappings.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
---

This version incorporates changes suggested by Mika Westerberg in
response to the draft patch I posted in Goodix thread.

 drivers/gpio/gpiolib.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index a18f00f..9631ee8 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1841,6 +1841,50 @@ static struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id,
 	return desc;
 }
 
+struct acpi_gpio_lookup {
+	struct list_head node;
+	struct acpi_device *adev;
+	const char *con_id;
+};
+
+static DEFINE_MUTEX(acpi_gpio_lookup_lock);
+static LIST_HEAD(acpi_gpio_lookup_list);
+
+static bool acpi_can_fallback_to_crs(struct acpi_device *adev,
+				     const char *con_id)
+{
+	struct acpi_gpio_lookup *l, *lookup = NULL;
+
+	/* Never fallback if the device has properties */
+	if (adev->data.properties || adev->driver_gpios)
+		return false;
+
+	mutex_lock(&acpi_gpio_lookup_lock);
+
+	list_for_each_entry(l, &acpi_gpio_lookup_list, node) {
+		if (l->adev == adev) {
+			lookup = l;
+			break;
+		}
+	}
+
+	if (!lookup) {
+		lookup = kmalloc(sizeof(*lookup), GFP_KERNEL);
+		if (lookup) {
+			lookup->adev = adev;
+			lookup->con_id = con_id;
+			list_add_tail(&lookup->node, &acpi_gpio_lookup_list);
+		}
+	}
+
+	mutex_unlock(&acpi_gpio_lookup_lock);
+
+	return lookup &&
+		((!lookup->con_id && !con_id) ||
+		 (lookup->con_id && con_id &&
+		  strcmp(lookup->con_id, con_id) == 0));
+}
+
 static struct gpio_desc *acpi_find_gpio(struct device *dev, const char *con_id,
 					unsigned int idx,
 					enum gpio_lookup_flags *flags)
@@ -1868,6 +1912,9 @@ static struct gpio_desc *acpi_find_gpio(struct device *dev, const char *con_id,
 
 	/* Then from plain _CRS GPIOs */
 	if (IS_ERR(desc)) {
+		if (!acpi_can_fallback_to_crs(adev, con_id))
+			return ERR_PTR(-ENOENT);
+
 		desc = acpi_get_gpiod_by_index(adev, NULL, idx, &info);
 		if (IS_ERR(desc))
 			return desc;
-- 
2.6.0.rc2.230.g3dd15c0


-- 
Dmitry
--
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