From khali@linux-fr.org Sat Jul 1 08:17:24 2006 Date: Sat, 1 Jul 2006 17:17:38 +0200 From: Jean Delvare To: Greg KH Subject: [PATCH 10/13] i2c-dev: Use a list for data storage Message-Id: <20060701171738.15fc3767.khali@linux-fr.org> Content-Disposition: inline; filename=i2c-dev-convert-array-to-list.patch 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 Signed-off-by: Greg Kroah-Hartman --- drivers/i2c/i2c-dev.c | 45 +++++++++++++++++++++++++-------------------- 1 file changed, 25 insertions(+), 20 deletions(-) --- gregkh-2.6.orig/drivers/i2c/i2c-dev.c +++ gregkh-2.6/drivers/i2c/i2c-dev.c @@ -32,6 +32,7 @@ #include #include #include +#include #include #include #include @@ -39,21 +40,27 @@ 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)