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-rw-r--r--Documentation/i2c/writing-clients51
1 files changed, 40 insertions, 11 deletions
diff --git a/Documentation/i2c/writing-clients b/Documentation/i2c/writing-clients
index d4cd4126d1a..6b61b3a2e90 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)
---------------------------------------
@@ -569,7 +598,6 @@ SMBus communication
in terms of it. Never use this function directly!
- extern s32 i2c_smbus_write_quick(struct i2c_client * client, u8 value);
extern s32 i2c_smbus_read_byte(struct i2c_client * client);
extern s32 i2c_smbus_write_byte(struct i2c_client * client, u8 value);
extern s32 i2c_smbus_read_byte_data(struct i2c_client * client, u8 command);
@@ -578,30 +606,31 @@ SMBus communication
extern s32 i2c_smbus_read_word_data(struct i2c_client * client, u8 command);
extern s32 i2c_smbus_write_word_data(struct i2c_client * client,
u8 command, u16 value);
+ extern s32 i2c_smbus_read_block_data(struct i2c_client * client,
+ u8 command, u8 *values);
extern s32 i2c_smbus_write_block_data(struct i2c_client * client,
u8 command, u8 length,
u8 *values);
extern s32 i2c_smbus_read_i2c_block_data(struct i2c_client * client,
u8 command, u8 length, u8 *values);
-
-These ones were removed in Linux 2.6.10 because they had no users, but could
-be added back later if needed:
-
- extern s32 i2c_smbus_read_block_data(struct i2c_client * client,
- u8 command, u8 *values);
extern s32 i2c_smbus_write_i2c_block_data(struct i2c_client * client,
u8 command, u8 length,
u8 *values);
+
+These ones were removed from i2c-core because they had no users, but could
+be added back later if needed:
+
+ extern s32 i2c_smbus_write_quick(struct i2c_client * client, u8 value);
extern s32 i2c_smbus_process_call(struct i2c_client * client,
u8 command, u16 value);
extern s32 i2c_smbus_block_process_call(struct i2c_client *client,
u8 command, u8 length,
u8 *values)
-All these transactions return -1 on failure. The 'write' transactions
-return 0 on success; the 'read' transactions return the read value, except
-for read_block, which returns the number of values read. The block buffers
-need not be longer than 32 bytes.
+All these transactions return a negative errno value on failure. The 'write'
+transactions return 0 on success; the 'read' transactions return the read
+value, except for block transactions, which return the number of values
+read. The block buffers need not be longer than 32 bytes.
You can read the file `smbus-protocol' for more information about the
actual SMBus protocol.