linux-kernel - [PATCH 2/2] als: add unique device-ids to the als device class

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Message-Id: <1259581598-16176-1-git-send-email-amit.kucheria@verdurent.com>
Date:	Mon, 30 Nov 2009 13:46:38 +0200
From:	Amit Kucheria <amit.kucheria@...durent.com>
To:	List Linux Kernel <linux-kernel@...r.kernel.org>
Cc:	rui.zhang@...el.com, jic23@....ac.uk, khali@...ux-fr.org,
	alan@...ux.intel.com, linux-acpi@...r.kernel.org, gregkh@...e.de
Subject: [PATCH 2/2] als: add unique device-ids to the als device class

Other devices classes such as hwmon and input class handle assignment of
unique device-ids inside the core functions instead of pushing it out to
individual drivers. This reduces code duplication and resulting bugs.

V2 - Updated the header to reflect the change is signature of
als_device_register(). Thanks to Jean for the review.

V1 - Add capability to als core to create unique ids

Signed-off-by: Amit Kucheria <amit.kucheria@...durent.com>
Acked-by: Jean Delvare <khali@...ux-fr.org>
Acked-by: Jonathan Cameron <jic23@....ac.uk>
---
 drivers/als/als_sys.c   |   48 ++++++++++++++++++++++++++++++++++++++++++++--
 include/linux/als_sys.h |    2 +-
 2 files changed, 46 insertions(+), 4 deletions(-)

diff --git a/drivers/als/als_sys.c b/drivers/als/als_sys.c
index e1d6395..aa15ad8 100644
--- a/drivers/als/als_sys.c
+++ b/drivers/als/als_sys.c
@@ -26,22 +26,55 @@
 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/kdev_t.h>
+#include <linux/idr.h>
 
 MODULE_AUTHOR("Zhang Rui <rui.zhang@...el.com>");
 MODULE_DESCRIPTION("Ambient Light Sensor sysfs/class support");
 MODULE_LICENSE("GPL");
 
+#define ALS_ID_PREFIX "als"
+#define ALS_ID_FORMAT ALS_ID_PREFIX "%d"
+
 static struct class *als_class;
 
+static DEFINE_IDR(als_idr);
+static DEFINE_SPINLOCK(idr_lock);
+
 /**
  * als_device_register - register a new Ambient Light Sensor class device
  * @parent:	the device to register.
  *
  * Returns the pointer to the new device
  */
-struct device *als_device_register(struct device *dev, char *name)
+struct device *als_device_register(struct device *dev)
 {
-	return device_create(als_class, dev, MKDEV(0, 0), NULL, name);
+	int id, err;
+	struct device *alsdev;
+
+again:
+	if (unlikely(idr_pre_get(&als_idr, GFP_KERNEL) == 0))
+		return ERR_PTR(-ENOMEM);
+
+	spin_lock(&idr_lock);
+	err = idr_get_new(&als_idr, NULL, &id);
+	spin_unlock(&idr_lock);
+
+	if (unlikely(err == -EAGAIN))
+		goto again;
+	else if (unlikely(err))
+		return ERR_PTR(err);
+
+	id = id & MAX_ID_MASK;
+	alsdev = device_create(als_class, dev, MKDEV(0, 0), NULL,
+			ALS_ID_FORMAT, id);
+
+	if (IS_ERR(alsdev)) {
+		spin_lock(&idr_lock);
+		idr_remove(&als_idr, id);
+		spin_unlock(&idr_lock);
+	}
+
+	return alsdev;
 }
 EXPORT_SYMBOL(als_device_register);
 
@@ -51,7 +84,16 @@ EXPORT_SYMBOL(als_device_register);
  */
 void als_device_unregister(struct device *dev)
 {
-	device_unregister(dev);
+	int id;
+
+	if (likely(sscanf(dev_name(dev), ALS_ID_FORMAT, &id) == 1)) {
+		device_unregister(dev);
+		spin_lock(&idr_lock);
+		idr_remove(&als_idr, id);
+		spin_unlock(&idr_lock);
+	} else
+		dev_dbg(dev->parent,
+			"als_device_unregister() failed: bad class ID!\n");
 }
 EXPORT_SYMBOL(als_device_unregister);
 
diff --git a/include/linux/als_sys.h b/include/linux/als_sys.h
index 500f300..41793f7 100644
--- a/include/linux/als_sys.h
+++ b/include/linux/als_sys.h
@@ -29,7 +29,7 @@
 #define ALS_ILLUMINANCE_MIN 0
 #define ALS_ILLUMINANCE_MAX -1
 
-struct device *als_device_register(struct device *dev, char *name);
+struct device *als_device_register(struct device *dev);
 void als_device_unregister(struct device *dev);
 
 #endif /* __ALS_SYS_H__ */
-- 
1.6.3.3

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