i2c: Migration aids for i2c_adapter.dev removal

Flag i2c_adapter.dev for removal after userspace tools get upgraded, and
include a near-term code migration aid to facilitate this:

 - The class device gets the name attribute it should have had.  This
   was previously (wrongly) associated with the i2c_adapter.dev node.
   Sysfs based tools and libraries can start converting right away.

 - Issue a warning for legacy adapter drivers that don't provide any
   physical device node; so systems with those drivers will know to
   fix this problem earlier.

This is one of a series of patches to help the I2C stack become a better
citizen of the Linux Driver Model world.

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

2 files changed, 41 insertions, 4 deletions

diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index 30f3c8c9c12a..f2024df7ebe5 100644
--- a/Documentation/feature-removal-schedule.txt
+++ b/Documentation/feature-removal-schedule.txt
@@ -226,6 +226,23 @@ Who:	Jean Delvare <khali@linux-fr.org>
 
 ---------------------------
 
+What:   i2c_adapter.dev
+        i2c_adapter.list
+When:   July 2007
+Why:    Superfluous, given i2c_adapter.class_dev:
+          * The "dev" was a stand-in for the physical device node that legacy
+            drivers would not have; but now it's almost always present.  Any
+            remaining legacy drivers must upgrade (they now trigger warnings).
+          * The "list" duplicates class device children.
+        The delay in removing this is so upgraded lm_sensors and libsensors
+        can get deployed.  (Removal causes minor changes in the sysfs layout,
+        notably the location of the adapter type name and parenting the i2c
+        client hardware directly from their controller.)
+Who:    Jean Delvare <khali@linux-fr.org>,
+        David Brownell <dbrownell@users.sourceforge.net>
+
+---------------------------
+
 What:   IPv4 only connection tracking/NAT/helpers
 When:   2.6.22
 Why:    The new layer 3 independant connection tracking replaces the old
diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index 3e31f1d265c9..b05378a3d673 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -95,16 +95,32 @@ struct device_driver i2c_adapter_driver = {
         .bus = &i2c_bus_type,
 };
 
+/* ------------------------------------------------------------------------- */
+
+/* I2C bus adapters -- one roots each I2C or SMBUS segment */
+
 static void i2c_adapter_class_dev_release(struct class_device *dev)
 {
         struct i2c_adapter *adap = class_dev_to_i2c_adapter(dev);
         complete(&adap->class_dev_released);
 }
 
+static ssize_t i2c_adapter_show_name(struct class_device *cdev, char *buf)
+{
+        struct i2c_adapter *adap = class_dev_to_i2c_adapter(cdev);
+        return sprintf(buf, "%s\n", adap->name);
+}
+
+static struct class_device_attribute i2c_adapter_attrs[] = {
+        __ATTR(name, S_IRUGO, i2c_adapter_show_name, NULL),
+        { },
+};
+
 struct class i2c_adapter_class = {
-        .owner =        THIS_MODULE,
-        .name =         "i2c-adapter",
-        .release =      &i2c_adapter_class_dev_release,
+        .owner                  = THIS_MODULE,
+        .name                   = "i2c-adapter",
+        .class_dev_attrs        = i2c_adapter_attrs,
+        .release                = &i2c_adapter_class_dev_release,
 };
 
 static ssize_t show_adapter_name(struct device *dev, struct device_attribute *attr, char *buf)
@@ -175,8 +191,12 @@ int i2c_add_adapter(struct i2c_adapter *adap)
          * If the parent pointer is not set up,
          * we add this adapter to the host bus.
          */
-        if (adap->dev.parent == NULL)
+        if (adap->dev.parent == NULL) {
                 adap->dev.parent = &platform_bus;
+                printk(KERN_WARNING "**WARNING** I2C adapter driver [%s] "
+                       "forgot to specify physical device; fix it!\n",
+                       adap->name);
+        }
         sprintf(adap->dev.bus_id, "i2c-%d", adap->nr);
         adap->dev.driver = &i2c_adapter_driver;
         adap->dev.release = &i2c_adapter_dev_release;