i2c: Add detection capability to new-style drivers

Add a mechanism to let new-style i2c drivers optionally autodetect
devices they would support on selected buses and ask i2c-core to
instantiate them. This is a replacement for legacy i2c drivers, much
cleaner.

Where drivers had to implement both a legacy i2c_driver and a
new-style i2c_driver so far, this mechanism makes it possible to get
rid of the legacy i2c_driver and implement both enumerated and
detected device support with just one (new-style) i2c_driver.

Here is a quick conversion guide for these drivers, step by step:

* Delete the legacy driver definition, registration and removal.
  Delete the attach_adapter and detach_client methods of the legacy
  driver.

* Change the prototype of the legacy detect function from
    static int foo_detect(struct i2c_adapter *adapter, int address, int kind);
  to
    static int foo_detect(struct i2c_client *client, int kind,
    			  struct i2c_board_info *info);

* Set the new-style driver detect callback to this new function, and
  set its address_data to &addr_data (addr_data is generally provided
  by I2C_CLIENT_INSMOD.)

* Add the appropriate class to the new-style driver. This is
  typically the class the legacy attach_adapter method was checking
  for. Class checking is now mandatory (done by i2c-core.) See
  <linux/i2c.h> for the list of available classes.

* Remove the i2c_client allocation and freeing from the detect
  function. A pre-allocated client is now handed to you by i2c-core,
  and is freed automatically.

* Make the detect function fill the type field of the i2c_board_info
  structure it was passed as a parameter, and return 0, on success. If
  the detection fails, return -ENODEV.

Signed-off-by: Jean Delvare <khali@linux-fr.org>

3 files changed, 272 insertions, 16 deletions

diff --git a/Documentation/i2c/writing-clients b/Documentation/i2c/writing-clients
index 63722d3c9cdf..6b61b3a2e90b 100644
--- a/Documentation/i2c/writing-clients
+++ b/Documentation/i2c/writing-clients
@@ -44,6 +44,10 @@ static struct i2c_driver foo_driver = {
         .id_table       = foo_ids,
         .probe          = foo_probe,
         .remove         = foo_remove,
+        /* if device autodetection is needed: */
+        .class          = I2C_CLASS_SOMETHING,
+        .detect         = foo_detect,
+        .address_data   = &addr_data,
 
         /* else, driver uses "legacy" binding model: */
         .attach_adapter = foo_attach_adapter,
@@ -217,6 +221,31 @@ in the I2C bus driver. You may want to save the returned i2c_client
 reference for later use.
 
 
+Device Detection (Standard driver model)
+----------------------------------------
+
+Sometimes you do not know in advance which I2C devices are connected to
+a given I2C bus.  This is for example the case of hardware monitoring
+devices on a PC's SMBus.  In that case, you may want to let your driver
+detect supported devices automatically.  This is how the legacy model
+was working, and is now available as an extension to the standard
+driver model (so that we can finally get rid of the legacy model.)
+
+You simply have to define a detect callback which will attempt to
+identify supported devices (returning 0 for supported ones and -ENODEV
+for unsupported ones), a list of addresses to probe, and a device type
+(or class) so that only I2C buses which may have that type of device
+connected (and not otherwise enumerated) will be probed.  The i2c
+core will then call you back as needed and will instantiate a device
+for you for every successful detection.
+
+Note that this mechanism is purely optional and not suitable for all
+devices.  You need some reliable way to identify the supported devices
+(typically using device-specific, dedicated identification registers),
+otherwise misdetections are likely to occur and things can get wrong
+quickly.
+
+
 Device Deletion (Standard driver model)
 ---------------------------------------
 
diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index 5e249d758828..0a79f7661017 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -42,7 +42,9 @@
 static DEFINE_MUTEX(core_lock);
 static DEFINE_IDR(i2c_adapter_idr);
 
-#define is_newstyle_driver(d) ((d)->probe || (d)->remove)
+#define is_newstyle_driver(d) ((d)->probe || (d)->remove || (d)->detect)
+
+static int i2c_detect(struct i2c_adapter *adapter, struct i2c_driver *driver);
 
 /* ------------------------------------------------------------------------- */
 
@@ -418,6 +420,10 @@ static int i2c_do_add_adapter(struct device_driver *d, void *data)
         struct i2c_driver *driver = to_i2c_driver(d);
         struct i2c_adapter *adap = data;
 
+        /* Detect supported devices on that bus, and instantiate them */
+        i2c_detect(adap, driver);
+
+        /* Let legacy drivers scan this bus for matching devices */
         if (driver->attach_adapter) {
                 /* We ignore the return code; if it fails, too bad */
                 driver->attach_adapter(adap);
@@ -457,7 +463,7 @@ static int i2c_register_adapter(struct i2c_adapter *adap)
         if (adap->nr < __i2c_first_dynamic_bus_num)
                 i2c_scan_static_board_info(adap);
 
-        /* let legacy drivers scan this bus for matching devices */
+        /* Notify drivers */
         dummy = bus_for_each_drv(&i2c_bus_type, NULL, adap,
                                  i2c_do_add_adapter);
 
@@ -563,8 +569,19 @@ static int i2c_do_del_adapter(struct device_driver *d, void *data)
 {
         struct i2c_driver *driver = to_i2c_driver(d);
         struct i2c_adapter *adapter = data;
+        struct i2c_client *client, *_n;
         int res;
 
+        /* Remove the devices we created ourselves */
+        list_for_each_entry_safe(client, _n, &driver->clients, detected) {
+                if (client->adapter == adapter) {
+                        dev_dbg(&adapter->dev, "Removing %s at 0x%x\n",
+                                client->name, client->addr);
+                        list_del(&client->detected);
+                        i2c_unregister_device(client);
+                }
+        }
+
         if (!driver->detach_adapter)
                 return 0;
         res = driver->detach_adapter(adapter);
@@ -651,7 +668,11 @@ static int __attach_adapter(struct device *dev, void *data)
         struct i2c_adapter *adapter = to_i2c_adapter(dev);
         struct i2c_driver *driver = data;
 
-        driver->attach_adapter(adapter);
+        i2c_detect(adapter, driver);
+
+        /* Legacy drivers scan i2c busses directly */
+        if (driver->attach_adapter)
+                driver->attach_adapter(adapter);
 
         return 0;
 }
@@ -695,10 +716,9 @@ int i2c_register_driver(struct module *owner, struct i2c_driver *driver)
 
         pr_debug("i2c-core: driver [%s] registered\n", driver->driver.name);
 
-        /* legacy drivers scan i2c busses directly */
-        if (driver->attach_adapter)
-                class_for_each_device(&i2c_adapter_class, driver,
-                                      __attach_adapter);
+        INIT_LIST_HEAD(&driver->clients);
+        /* Walk the adapters that are already present */
+        class_for_each_device(&i2c_adapter_class, driver, __attach_adapter);
 
         mutex_unlock(&core_lock);
         return 0;
@@ -709,6 +729,17 @@ static int __detach_adapter(struct device *dev, void *data)
 {
         struct i2c_adapter *adapter = to_i2c_adapter(dev);
         struct i2c_driver *driver = data;
+        struct i2c_client *client, *_n;
+
+        list_for_each_entry_safe(client, _n, &driver->clients, detected) {
+                dev_dbg(&adapter->dev, "Removing %s at 0x%x\n",
+                        client->name, client->addr);
+                list_del(&client->detected);
+                i2c_unregister_device(client);
+        }
+
+        if (is_newstyle_driver(driver))
+                return 0;
 
         /* Have a look at each adapter, if clients of this driver are still
          * attached. If so, detach them to be able to kill the driver
@@ -747,10 +778,7 @@ void i2c_del_driver(struct i2c_driver *driver)
 {
         mutex_lock(&core_lock);
 
-        /* legacy driver? */
-        if (!is_newstyle_driver(driver))
-                class_for_each_device(&i2c_adapter_class, driver,
-                                      __detach_adapter);
+        class_for_each_device(&i2c_adapter_class, driver, __detach_adapter);
 
         driver_unregister(&driver->driver);
         pr_debug("i2c-core: driver [%s] unregistered\n", driver->driver.name);
@@ -1205,6 +1233,179 @@ int i2c_probe(struct i2c_adapter *adapter,
 }
 EXPORT_SYMBOL(i2c_probe);
 
+/* Separate detection function for new-style drivers */
+static int i2c_detect_address(struct i2c_client *temp_client, int kind,
+                              struct i2c_driver *driver)
+{
+        struct i2c_board_info info;
+        struct i2c_adapter *adapter = temp_client->adapter;
+        int addr = temp_client->addr;
+        int err;
+
+        /* Make sure the address is valid */
+        if (addr < 0x03 || addr > 0x77) {
+                dev_warn(&adapter->dev, "Invalid probe address 0x%02x\n",
+                         addr);
+                return -EINVAL;
+        }
+
+        /* Skip if already in use */
+        if (i2c_check_addr(adapter, addr))
+                return 0;
+
+        /* Make sure there is something at this address, unless forced */
+        if (kind < 0) {
+                if (i2c_smbus_xfer(adapter, addr, 0, 0, 0,
+                                   I2C_SMBUS_QUICK, NULL) < 0)
+                        return 0;
+
+                /* prevent 24RF08 corruption */
+                if ((addr & ~0x0f) == 0x50)
+                        i2c_smbus_xfer(adapter, addr, 0, 0, 0,
+                                       I2C_SMBUS_QUICK, NULL);
+        }
+
+        /* Finally call the custom detection function */
+        memset(&info, 0, sizeof(struct i2c_board_info));
+        info.addr = addr;
+        err = driver->detect(temp_client, kind, &info);
+        if (err) {
+                /* -ENODEV is returned if the detection fails. We catch it
+                   here as this isn't an error. */
+                return err == -ENODEV ? 0 : err;
+        }
+
+        /* Consistency check */
+        if (info.type[0] == '\0') {
+                dev_err(&adapter->dev, "%s detection function provided "
+                        "no name for 0x%x\n", driver->driver.name,
+                        addr);
+        } else {
+                struct i2c_client *client;
+
+                /* Detection succeeded, instantiate the device */
+                dev_dbg(&adapter->dev, "Creating %s at 0x%02x\n",
+                        info.type, info.addr);
+                client = i2c_new_device(adapter, &info);
+                if (client)
+                        list_add_tail(&client->detected, &driver->clients);
+                else
+                        dev_err(&adapter->dev, "Failed creating %s at 0x%02x\n",
+                                info.type, info.addr);
+        }
+        return 0;
+}
+
+static int i2c_detect(struct i2c_adapter *adapter, struct i2c_driver *driver)
+{
+        const struct i2c_client_address_data *address_data;
+        struct i2c_client *temp_client;
+        int i, err = 0;
+        int adap_id = i2c_adapter_id(adapter);
+
+        address_data = driver->address_data;
+        if (!driver->detect || !address_data)
+                return 0;
+
+        /* Set up a temporary client to help detect callback */
+        temp_client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL);
+        if (!temp_client)
+                return -ENOMEM;
+        temp_client->adapter = adapter;
+
+        /* Force entries are done first, and are not affected by ignore
+           entries */
+        if (address_data->forces) {
+                const unsigned short * const *forces = address_data->forces;
+                int kind;
+
+                for (kind = 0; forces[kind]; kind++) {
+                        for (i = 0; forces[kind][i] != I2C_CLIENT_END;
+                             i += 2) {
+                                if (forces[kind][i] == adap_id
+                                 || forces[kind][i] == ANY_I2C_BUS) {
+                                        dev_dbg(&adapter->dev, "found force "
+                                                "parameter for adapter %d, "
+                                                "addr 0x%02x, kind %d\n",
+                                                adap_id, forces[kind][i + 1],
+                                                kind);
+                                        temp_client->addr = forces[kind][i + 1];
+                                        err = i2c_detect_address(temp_client,
+                                                kind, driver);
+                                        if (err)
+                                                goto exit_free;
+                                }
+                        }
+                }
+        }
+
+        /* Stop here if we can't use SMBUS_QUICK */
+        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_QUICK)) {
+                if (address_data->probe[0] == I2C_CLIENT_END
+                 && address_data->normal_i2c[0] == I2C_CLIENT_END)
+                        goto exit_free;
+
+                dev_warn(&adapter->dev, "SMBus Quick command not supported, "
+                         "can't probe for chips\n");
+                err = -EOPNOTSUPP;
+                goto exit_free;
+        }
+
+        /* Stop here if the classes do not match */
+        if (!(adapter->class & driver->class))
+                goto exit_free;
+
+        /* Probe entries are done second, and are not affected by ignore
+           entries either */
+        for (i = 0; address_data->probe[i] != I2C_CLIENT_END; i += 2) {
+                if (address_data->probe[i] == adap_id
+                 || address_data->probe[i] == ANY_I2C_BUS) {
+                        dev_dbg(&adapter->dev, "found probe parameter for "
+                                "adapter %d, addr 0x%02x\n", adap_id,
+                                address_data->probe[i + 1]);
+                        temp_client->addr = address_data->probe[i + 1];
+                        err = i2c_detect_address(temp_client, -1, driver);
+                        if (err)
+                                goto exit_free;
+                }
+        }
+
+        /* Normal entries are done last, unless shadowed by an ignore entry */
+        for (i = 0; address_data->normal_i2c[i] != I2C_CLIENT_END; i += 1) {
+                int j, ignore;
+
+                ignore = 0;
+                for (j = 0; address_data->ignore[j] != I2C_CLIENT_END;
+                     j += 2) {
+                        if ((address_data->ignore[j] == adap_id ||
+                             address_data->ignore[j] == ANY_I2C_BUS)
+                         && address_data->ignore[j + 1]
+                            == address_data->normal_i2c[i]) {
+                                dev_dbg(&adapter->dev, "found ignore "
+                                        "parameter for adapter %d, "
+                                        "addr 0x%02x\n", adap_id,
+                                        address_data->ignore[j + 1]);
+                                ignore = 1;
+                                break;
+                        }
+                }
+                if (ignore)
+                        continue;
+
+                dev_dbg(&adapter->dev, "found normal entry for adapter %d, "
+                        "addr 0x%02x\n", adap_id,
+                        address_data->normal_i2c[i]);
+                temp_client->addr = address_data->normal_i2c[i];
+                err = i2c_detect_address(temp_client, -1, driver);
+                if (err)
+                        goto exit_free;
+        }
+
+ exit_free:
+        kfree(temp_client);
+        return err;
+}
+
 struct i2c_client *
 i2c_new_probed_device(struct i2c_adapter *adap,
                       struct i2c_board_info *info,
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 50cbab4b62b0..08be0d21864c 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -45,6 +45,7 @@ struct i2c_adapter;
 struct i2c_client;
 struct i2c_driver;
 union i2c_smbus_data;
+struct i2c_board_info;
 
 /*
  * The master routines are the ones normally used to transmit data to devices
@@ -94,15 +95,33 @@ extern s32 i2c_smbus_write_i2c_block_data(struct i2c_client * client,
                                           u8 command, u8 length,
                                           const u8 *values);
 
-/*
- * A driver is capable of handling one or more physical devices present on
- * I2C adapters. This information is used to inform the driver of adapter
- * events.
+/**
+ * struct i2c_driver - represent an I2C device driver
+ * @class: What kind of i2c device we instantiate (for detect)
+ * @detect: Callback for device detection
+ * @address_data: The I2C addresses to probe, ignore or force (for detect)
+ * @clients: List of detected clients we created (for i2c-core use only)
  *
  * The driver.owner field should be set to the module owner of this driver.
  * The driver.name field should be set to the name of this driver.
+ *
+ * For automatic device detection, both @detect and @address_data must
+ * be defined. @class should also be set, otherwise only devices forced
+ * with module parameters will be created. The detect function must
+ * fill at least the name field of the i2c_board_info structure it is
+ * handed upon successful detection, and possibly also the flags field.
+ *
+ * If @detect is missing, the driver will still work fine for enumerated
+ * devices. Detected devices simply won't be supported. This is expected
+ * for the many I2C/SMBus devices which can't be detected reliably, and
+ * the ones which can always be enumerated in practice.
+ *
+ * The i2c_client structure which is handed to the @detect callback is
+ * not a real i2c_client. It is initialized just enough so that you can
+ * call i2c_smbus_read_byte_data and friends on it. Don't do anything
+ * else with it. In particular, calling dev_dbg and friends on it is
+ * not allowed.
  */
-
 struct i2c_driver {
         int id;
         unsigned int class;
@@ -142,6 +161,11 @@ struct i2c_driver {
 
         struct device_driver driver;
         const struct i2c_device_id *id_table;
+
+        /* Device detection callback for automatic device creation */
+        int (*detect)(struct i2c_client *, int kind, struct i2c_board_info *);
+        const struct i2c_client_address_data *address_data;
+        struct list_head clients;
 };
 #define to_i2c_driver(d) container_of(d, struct i2c_driver, driver)
 
@@ -157,6 +181,7 @@ struct i2c_driver {
  * @dev: Driver model device node for the slave.
  * @irq: indicates the IRQ generated by this device (if any)
  * @list: list of active/busy clients (DEPRECATED)
+ * @detected: member of an i2c_driver.clients list
  * @released: used to synchronize client releases & detaches and references
  *
  * An i2c_client identifies a single device (i.e. chip) connected to an
@@ -174,6 +199,7 @@ struct i2c_client {
         struct device dev;              /* the device structure         */
         int irq;                        /* irq issued by device         */
         struct list_head list;          /* DEPRECATED */
+        struct list_head detected;
         struct completion released;
 };
 #define to_i2c_client(d) container_of(d, struct i2c_client, dev)