From: Jean Delvare <khali at linux-fr.org>
i2c-dev: Use a list for data storage
Use a list instead of a static array for storing the i2c-dev data.
Given that most systems have less than 10 i2c busses, most of the
space was wasted, so this saves around 1 kB of memory (2 kB on 64-bit
archs.)
The drawback is that lookup was in O(1) and is now in O(N), but given
that the values of N are always small, I don't think this is a problem.
Signed-off-by: Jean Delvare <khali at linux-fr.org>
Signed-off-by: Greg Kroah-Hartman <gregkh at suse.de>
---
drivers/i2c/i2c-dev.c | 45 +++++++++++++++++++++++++--------------------
1 files changed, 25 insertions(+), 20 deletions(-)
diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c
index 6e90dec..206e805 100644
--- a/drivers/i2c/i2c-dev.c
+++ b/drivers/i2c/i2c-dev.c
@@ -32,6 +32,7 @@ #include <linux/fs.h>
#include <linux/slab.h>
#include <linux/smp_lock.h>
#include <linux/init.h>
+#include <linux/list.h>
#include <linux/i2c.h>
#include <linux/i2c-dev.h>
#include <asm/uaccess.h>
@@ -39,21 +40,27 @@ #include <asm/uaccess.h>
static struct i2c_client i2cdev_client_template;
struct i2c_dev {
+ struct list_head list;
struct i2c_adapter *adap;
struct class_device *class_dev;
};
#define I2C_MINORS 256
-static struct i2c_dev *i2c_dev_array[I2C_MINORS];
-static DEFINE_SPINLOCK(i2c_dev_array_lock);
+static LIST_HEAD(i2c_dev_list);
+static DEFINE_SPINLOCK(i2c_dev_list_lock);
static struct i2c_dev *i2c_dev_get_by_minor(unsigned index)
{
struct i2c_dev *i2c_dev;
- spin_lock(&i2c_dev_array_lock);
- i2c_dev = i2c_dev_array[index];
- spin_unlock(&i2c_dev_array_lock);
+ spin_lock(&i2c_dev_list_lock);
+ list_for_each_entry(i2c_dev, &i2c_dev_list, list) {
+ if (i2c_dev->adap->nr == index)
+ goto found;
+ }
+ i2c_dev = NULL;
+found:
+ spin_unlock(&i2c_dev_list_lock);
return i2c_dev;
}
@@ -61,30 +68,28 @@ static struct i2c_dev *get_free_i2c_dev(
{
struct i2c_dev *i2c_dev;
+ if (adap->nr >= I2C_MINORS) {
+ printk(KERN_ERR "i2c-dev: Out of device minors (%d)\n",
+ adap->nr);
+ return ERR_PTR(-ENODEV);
+ }
+
i2c_dev = kzalloc(sizeof(*i2c_dev), GFP_KERNEL);
if (!i2c_dev)
return ERR_PTR(-ENOMEM);
-
- spin_lock(&i2c_dev_array_lock);
- if (i2c_dev_array[adap->nr]) {
- spin_unlock(&i2c_dev_array_lock);
- dev_err(&adap->dev, "i2c-dev already has a device assigned to this adapter\n");
- goto error;
- }
i2c_dev->adap = adap;
- i2c_dev_array[adap->nr] = i2c_dev;
- spin_unlock(&i2c_dev_array_lock);
+
+ spin_lock(&i2c_dev_list_lock);
+ list_add_tail(&i2c_dev->list, &i2c_dev_list);
+ spin_unlock(&i2c_dev_list_lock);
return i2c_dev;
-error:
- kfree(i2c_dev);
- return ERR_PTR(-ENODEV);
}
static void return_i2c_dev(struct i2c_dev *i2c_dev)
{
- spin_lock(&i2c_dev_array_lock);
- i2c_dev_array[i2c_dev->adap->nr] = NULL;
- spin_unlock(&i2c_dev_array_lock);
+ spin_lock(&i2c_dev_list_lock);
+ list_del(&i2c_dev->list);
+ spin_unlock(&i2c_dev_list_lock);
}
static ssize_t show_adapter_name(struct class_device *class_dev, char *buf)
--
1.4.2.1
