Commit 4735c98f authored by Jean Delvare's avatar Jean Delvare Committed by Jean Delvare
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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

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

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

* 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: default avatarJean Delvare <>
parent 8508159e
......@@ -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: */
.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
Device Deletion (Standard driver model)
......@@ -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 */
......@@ -457,7 +463,7 @@ static int i2c_register_adapter(struct i2c_adapter *adap)
if (adap->nr < __i2c_first_dynamic_bus_num)
/* let legacy drivers scan this bus for matching devices */
/* Notify drivers */
dummy = bus_for_each_drv(&i2c_bus_type, NULL, adap,
......@@ -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);
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;
i2c_detect(adapter, driver);
/* Legacy drivers scan i2c busses directly */
if (driver->attach_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->;
/* legacy drivers scan i2c busses directly */
if (driver->attach_adapter)
class_for_each_device(&i2c_adapter_class, driver,
/* Walk the adapters that are already present */
class_for_each_device(&i2c_adapter_class, driver, __attach_adapter);
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);
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)
/* legacy driver? */
if (!is_newstyle_driver(driver))
class_for_each_device(&i2c_adapter_class, driver,
class_for_each_device(&i2c_adapter_class, driver, __detach_adapter);
pr_debug("i2c-core: driver [%s] unregistered\n", driver->;
......@@ -1205,6 +1233,179 @@ int i2c_probe(struct i2c_adapter *adapter,
/* 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",
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,
return 0;
/* prevent 24RF08 corruption */
if ((addr & ~0x0f) == 0x50)
i2c_smbus_xfer(adapter, addr, 0, 0, 0,
/* 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->,
} 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);
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],
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");
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;
if (ignore)
dev_dbg(&adapter->dev, "found normal entry for adapter %d, "
"addr 0x%02x\n", adap_id,
temp_client->addr = address_data->normal_i2c[i];
err = i2c_detect_address(temp_client, -1, driver);
if (err)
goto exit_free;
return err;
struct i2c_client *
i2c_new_probed_device(struct i2c_adapter *adap,
struct i2c_board_info *info,
......@@ -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 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)
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