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i2c-dev: Use a list for data storage 

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@linux-fr.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Jean Delvare 2006-07-01 17:17:38 +02:00 committed by Greg Kroah-Hartman
parent 9455e4c9ab
commit f3b3aadbbd
1 changed files with 25 additions and 20 deletions
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45
drivers/i2c/i2c-dev.c
View File

@ -32,6 +32,7 @@
#include <linux/slab.h> #include <linux/slab.h>
#include <linux/smp_lock.h> #include <linux/smp_lock.h>
#include <linux/init.h> #include <linux/init.h>
#include <linux/list.h>
#include <linux/i2c.h> #include <linux/i2c.h>
#include <linux/i2c-dev.h> #include <linux/i2c-dev.h>
#include <asm/uaccess.h> #include <asm/uaccess.h>
@ -39,21 +40,27 @@
static struct i2c_client i2cdev_client_template; static struct i2c_client i2cdev_client_template;
struct i2c_dev { struct i2c_dev {
struct list_head list;
struct i2c_adapter *adap; struct i2c_adapter *adap;
struct class_device *class_dev; struct class_device *class_dev;
}; };
#define I2C_MINORS 256 #define I2C_MINORS 256
static struct i2c_dev *i2c_dev_array[I2C_MINORS]; static LIST_HEAD(i2c_dev_list);
static DEFINE_SPINLOCK(i2c_dev_array_lock); static DEFINE_SPINLOCK(i2c_dev_list_lock);
static struct i2c_dev *i2c_dev_get_by_minor(unsigned index) static struct i2c_dev *i2c_dev_get_by_minor(unsigned index)
{ {
struct i2c_dev *i2c_dev; struct i2c_dev *i2c_dev;
spin_lock(&i2c_dev_array_lock); spin_lock(&i2c_dev_list_lock);
i2c_dev = i2c_dev_array[index]; list_for_each_entry(i2c_dev, &i2c_dev_list, list) {
spin_unlock(&i2c_dev_array_lock); if (i2c_dev->adap->nr == index)
goto found;
}
i2c_dev = NULL;
found:
spin_unlock(&i2c_dev_list_lock);
return i2c_dev; return i2c_dev;
} }
@ -61,30 +68,28 @@ static struct i2c_dev *get_free_i2c_dev(struct i2c_adapter *adap)
{ {
struct i2c_dev *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); i2c_dev = kzalloc(sizeof(*i2c_dev), GFP_KERNEL);
if (!i2c_dev) if (!i2c_dev)
return ERR_PTR(-ENOMEM); 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->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; return i2c_dev;
error:
kfree(i2c_dev);
return ERR_PTR(-ENODEV);
} }
static void return_i2c_dev(struct i2c_dev *i2c_dev) static void return_i2c_dev(struct i2c_dev *i2c_dev)
{ {
spin_lock(&i2c_dev_array_lock); spin_lock(&i2c_dev_list_lock);
i2c_dev_array[i2c_dev->adap->nr] = NULL; list_del(&i2c_dev->list);
spin_unlock(&i2c_dev_array_lock); spin_unlock(&i2c_dev_list_lock);
} }
static ssize_t show_adapter_name(struct class_device *class_dev, char *buf) static ssize_t show_adapter_name(struct class_device *class_dev, char *buf)