[PATCH] I2C: refactor message in i2c_detach_client

We could refactor the error message 34 different i2c drivers print if
i2c_detach_client() fails in this function itself. Saves quite a few
lines of code. Documentation is updated to reflect that change.

Note that this patch should be applied after Rudolf Marek's w83792d
patches.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index 7a7837a..b0bceb2 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -449,8 +449,12 @@
 	struct i2c_adapter *adapter = client->adapter;
 	int res = 0;
 	
-	if ((client->flags & I2C_CLIENT_ALLOW_USE) && (client->usage_count > 0))
+	if ((client->flags & I2C_CLIENT_ALLOW_USE)
+	 && (client->usage_count > 0)) {
+		dev_warn(&client->dev, "Client [%s] still busy, "
+			 "can't detach\n", client->name);
 		return -EBUSY;
+	}
 
 	if (adapter->client_unregister)  {
 		res = adapter->client_unregister(client);