[PATCH 1/4] i2c: Introduce i2c listeners

[Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org>]

Add an i2c listener mechanism to the i2c-subsystem. This mechanism
lets device drivers be notified of addition and removal of adapters,
and gives them a chance to detect devices they would support and to ask
i2c-core to instantiate them.

Signed-off-by: Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org>
---
This patch depends on:
http://khali.linux-fr.org/devel/linux-2.6/jdelvare-i2c/i2c-use-class_for_each_device.patch

Implementation note: i2c_detect and i2c_detect_address are basically
clones of i2c_probe and i2c_probe_address but operating on a callback
with a slightly different prototype. This duplicated code accounts
for a large part of the patch, but once legacy drivers are gone,
i2c_probe and i2c_probe_address will be removed, so thus is no
long-term duplication.

 drivers/i2c/i2c-core.c |  235 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/i2c.h    |   34 ++++++
 2 files changed, 269 insertions(+)

--- linux-2.6.26-rc4.orig/include/linux/i2c.h	2008-06-04 08:26:05.000000000 +0200
+++ linux-2.6.26-rc4/include/linux/i2c.h	2008-06-04 08:26:05.000000000 +0200
@@ -43,6 +43,7 @@ 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
@@ -92,6 +93,34 @@ extern s32 i2c_smbus_write_i2c_block_dat
 					  u8 command, u8 length,
 					  const u8 *values);
 
+/**
+ * struct i2c_listener - Be informed of adapter addition and removal
+ * @class: What kind of i2c device the listener may instantiate
+ * @attach_adapter: Called after adapter addition (unimplemented)
+ * @detach_adapter: Called before adapter removal (unimplemented)
+ * @address_data: The I2C addresses to probe, ignore or force
+ * @detect: Callback for device detection
+ * @clients: List of detected clients we created
+ *
+ * The @detect callback returns an i2c_board_info structure for device
+ * creation if the detection was successful, NULL otherwise.
+ *
+ * The @clients list is handled by i2c-core.
+ */
+struct i2c_listener {
+	unsigned int class;
+
+	int (*attach_adapter)(struct i2c_adapter *);
+	int (*detach_adapter)(struct i2c_adapter *);
+
+	const struct i2c_client_address_data *address_data;
+	int (*detect)(struct i2c_adapter *, int address, int kind,
+		      struct i2c_board_info *);
+	struct list_head clients;
+
+	struct list_head list;
+};
+
 /*
  * 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
@@ -155,6 +184,7 @@ 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 i2c_listener.clients
  * @released: used to synchronize client releases & detaches and references
  *
  * An i2c_client identifies a single device (i.e. chip) connected to an
@@ -172,6 +202,7 @@ struct i2c_client {
 	struct device dev;		/* the device structure		*/
 	int irq;			/* irq issued by device (or -1) */
 	struct list_head list;		/* DEPRECATED */
+	struct list_head detected;
 	struct completion released;
 };
 #define to_i2c_client(d) container_of(d, struct i2c_client, dev)
@@ -382,6 +413,9 @@ extern int i2c_add_adapter(struct i2c_ad
 extern int i2c_del_adapter(struct i2c_adapter *);
 extern int i2c_add_numbered_adapter(struct i2c_adapter *);
 
+extern void i2c_add_listener(struct i2c_listener *);
+extern void i2c_del_listener(struct i2c_listener *);
+
 extern int i2c_register_driver(struct module *, struct i2c_driver *);
 extern void i2c_del_driver(struct i2c_driver *);
 
--- linux-2.6.26-rc4.orig/drivers/i2c/i2c-core.c	2008-06-04 08:26:05.000000000 +0200
+++ linux-2.6.26-rc4/drivers/i2c/i2c-core.c	2008-06-04 11:38:02.000000000 +0200
@@ -42,8 +42,16 @@
 static DEFINE_MUTEX(core_lock);
 static DEFINE_IDR(i2c_adapter_idr);
 
+/* listeners_lock protects the listeners list. If you need both core_lock
+   and listeners_lock, core_lock must be taken first. */
+static DEFINE_MUTEX(listeners_lock);
+static LIST_HEAD(listeners);
+
 #define is_newstyle_driver(d) ((d)->probe || (d)->remove)
 
+static int i2c_detect(struct i2c_adapter *adapter,
+		      struct i2c_listener *listener);
+
 /* ------------------------------------------------------------------------- */
 
 static const struct i2c_device_id *i2c_match_id(const struct i2c_device_id *id,
@@ -418,6 +426,7 @@ static int i2c_do_add_adapter(struct dev
 
 static int i2c_register_adapter(struct i2c_adapter *adap)
 {
+	struct i2c_listener *listener;
 	int res = 0, dummy;
 
 	mutex_init(&adap->bus_lock);
@@ -448,6 +457,13 @@ static int i2c_register_adapter(struct i
 	if (adap->nr < __i2c_first_dynamic_bus_num)
 		i2c_scan_static_board_info(adap);
 
+	/* let listeners know that a bus has arrived */
+	mutex_lock(&listeners_lock);
+	list_for_each_entry(listener, &listeners, list) {
+		i2c_detect(adap, listener);
+	}
+	mutex_unlock(&listeners_lock);
+
 	/* let legacy drivers scan this bus for matching devices */
 	dummy = bus_for_each_drv(&i2c_bus_type, NULL, adap,
 				 i2c_do_add_adapter);
@@ -576,6 +592,7 @@ static int i2c_do_del_adapter(struct dev
 int i2c_del_adapter(struct i2c_adapter *adap)
 {
 	struct i2c_client *client, *_n;
+	struct i2c_listener *listener;
 	int res = 0;
 
 	mutex_lock(&core_lock);
@@ -588,6 +605,21 @@ int i2c_del_adapter(struct i2c_adapter *
 		goto out_unlock;
 	}
 
+	/* Walk the listeners to remove the devices we created ourselves */
+	mutex_lock(&listeners_lock);
+	list_for_each_entry(listener, &listeners, list) {
+		list_for_each_entry_safe(client, _n, &listener->clients,
+					 detected) {
+			if (client->adapter == adap) {
+				dev_dbg(&adap->dev, "Removing %s at 0x%x\n",
+					client->name, client->addr);
+				list_del(&client->detected);
+				i2c_unregister_device(client);
+			}
+		}
+	}
+	mutex_unlock(&listeners_lock);
+
 	/* Tell drivers about this removal */
 	res = bus_for_each_drv(&i2c_bus_type, NULL, adap,
 			       i2c_do_del_adapter);
@@ -752,6 +784,53 @@ EXPORT_SYMBOL(i2c_del_driver);
 
 /* ------------------------------------------------------------------------- */
 
+static int __i2c_detect(struct device *dev, void *data)
+{
+	struct i2c_adapter *adapter = to_i2c_adapter(dev);
+	struct i2c_listener *listener = data;
+
+	i2c_detect(adapter, listener);
+
+	return 0;
+}
+
+void i2c_add_listener(struct i2c_listener *listener)
+{
+	mutex_lock(&core_lock);
+	mutex_lock(&listeners_lock);
+	INIT_LIST_HEAD(&listener->clients);
+	list_add_tail(&listener->list, &listeners);
+	pr_debug("i2c: Listener %p added\n", listener);
+
+	/* let this listener know about buses that are already there */
+	class_for_each_device(&i2c_adapter_class, listener, __i2c_detect);
+	mutex_unlock(&listeners_lock);
+	mutex_unlock(&core_lock);
+}
+EXPORT_SYMBOL_GPL(i2c_add_listener);
+
+void i2c_del_listener(struct i2c_listener *listener)
+{
+	struct i2c_client *client, *_n;
+
+	mutex_lock(&listeners_lock);
+	/* remove all clients that originate from this listener */
+	list_for_each_entry_safe(client, _n, &listener->clients, detected) {
+		dev_dbg(&client->adapter->dev, "Removing %s at 0x%x\n",
+			client->name, client->addr);
+		list_del(&client->detected);
+		i2c_unregister_device(client);
+	}
+
+	list_del(&listener->list);
+	pr_debug("i2c: Listener %p deleted\n", listener);
+	mutex_unlock(&listeners_lock);
+
+}
+EXPORT_SYMBOL_GPL(i2c_del_listener);
+
+/* ------------------------------------------------------------------------- */
+
 static int __i2c_check_addr(struct device *dev, void *addrp)
 {
 	struct i2c_client	*client = i2c_verify_client(dev);
@@ -1196,6 +1275,162 @@ int i2c_probe(struct i2c_adapter *adapte
 }
 EXPORT_SYMBOL(i2c_probe);
 
+/* Separate detection function for listeners */
+static int i2c_detect_address(struct i2c_adapter *adapter,
+			      int addr, int kind,
+			      struct i2c_listener *listener)
+{
+	struct i2c_board_info info;
+	struct i2c_client *client;
+	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));
+	err = listener->detect(adapter, addr, kind, &info);
+	if (err) {
+		/* -ENODEV can be returned if there is a chip at the given address
+		   but it isn't supported by this chip driver. We catch it here as
+		   this isn't an error. */
+		return err == -ENODEV ? 0 : err;
+	}
+
+	/* Consistency check */
+	if (info.type[0] == '\0' || info.addr != addr) {
+		dev_err(&adapter->dev, "Detection function returned "
+			"inconsistent data for 0x%x\n", addr);
+	} else {
+		/* Detection succeeded, instantiate the device */
+		dev_dbg(&adapter->dev, "Creating %s at 0x%x\n",
+			info.type, info.addr);
+		client = i2c_new_device(adapter, &info);
+		list_add_tail(&client->detected, &listener->clients);
+	}
+	return 0;
+}
+
+static int i2c_detect(struct i2c_adapter *adapter,
+		      struct i2c_listener *listener)
+{
+	const struct i2c_client_address_data *address_data;
+	int i, err;
+	int adap_id = i2c_adapter_id(adapter);
+
+	address_data = listener->address_data;
+
+	/* 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);
+					err = i2c_detect_address(adapter,
+						forces[kind][i + 1],
+						kind, listener);
+					if (err)
+						return err;
+				}
+			}
+		}
+	}
+
+	/* 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)
+			return 0;
+
+		dev_warn(&adapter->dev, "SMBus Quick command not supported, "
+			 "can't probe for chips\n");
+		return -EOPNOTSUPP;
+	}
+
+	/* 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]);
+			err = i2c_detect_address(adapter,
+						 address_data->probe[i + 1],
+						 -1, listener);
+			if (err)
+				return err;
+		}
+	}
+
+	/* Stop here if the classes do not match */
+	if (!(adapter->class & listener->class))
+		return 0;
+
+	/* 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]);
+		err = i2c_detect_address(adapter, address_data->normal_i2c[i],
+					 -1, listener);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
 struct i2c_client *
 i2c_new_probed_device(struct i2c_adapter *adap,
 		      struct i2c_board_info *info,

-- 
Jean Delvare

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