i2c: Shrink struct i2c_client

This shrinks the size of "struct i2c_client" by 40 bytes:

 - Substantially shrinks the string used to identify the chip type
 - The "flags" don't need to be so big
 - Removes some internal padding

It also adds kerneldoc for that struct, explaining how "name" is really a
chip type identifier; it's otherwise potentially confusing.

Because the I2C_NAME_SIZE symbol was abused for both i2c_client.name
and for i2c_adapter.name, this needed to affect i2c_adapter too.  The
adapters which used that symbol now use the more-obviously-correct
idiom of taking the size of that field.

JD: Shorten i2c_adapter.name from 50 to 48 bytes while we're here, to
avoid wasting space in padding.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

1 files changed, 14 insertions, 9 deletions

diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 47c2a1907372..953e71fb07b4 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -140,25 +140,30 @@ struct i2c_driver {
 };
 #define to_i2c_driver(d) container_of(d, struct i2c_driver, driver)
 
-#define I2C_NAME_SIZE   50
-
-/*
- * i2c_client identifies a single device (i.e. chip) that is connected to an
- * i2c bus. The behaviour is defined by the routines of the driver. This
- * function is mainly used for lookup & other admin. functions.
+#define I2C_NAME_SIZE   20
+
+/**
+ * struct i2c_client - represent an I2C slave device
+ * @addr: Address used on the I2C bus connected to the parent adapter.
+ * @name: Indicates the type of the device, usually a chip name that's
+ *      generic enough to hide second-sourcing and compatible revisions.
+ * @dev: Driver model device node for the slave.
+ *
+ * An i2c_client identifies a single device (i.e. chip) connected to an
+ * i2c bus. The behaviour is defined by the routines of the driver.
  */
 struct i2c_client {
-        unsigned int flags;             /* div., see below              */
+        unsigned short flags;           /* div., see below              */
         unsigned short addr;            /* chip address - NOTE: 7bit    */
                                         /* addresses are stored in the  */
                                         /* _LOWER_ 7 bits               */
+        char name[I2C_NAME_SIZE];
         struct i2c_adapter *adapter;    /* the adapter we sit on        */
         struct i2c_driver *driver;      /* and our access routines      */
         int usage_count;                /* How many accesses currently  */
                                         /* to the client                */
         struct device dev;              /* the device structure         */
         struct list_head list;
-        char name[I2C_NAME_SIZE];
         struct completion released;
 };
 #define to_i2c_client(d) container_of(d, struct i2c_client, dev)
@@ -231,7 +236,7 @@ struct i2c_adapter {
         int nr;
         struct list_head clients;
         struct list_head list;
-        char name[I2C_NAME_SIZE];
+        char name[48];
         struct completion dev_released;
 };
 #define dev_to_i2c_adapter(d) container_of(d, struct i2c_adapter, dev)