i2c: Delete legacy model documentation
The legacy i2c binding model is deprecated and will be removed soon, so we no longer need to document it. Signed-off-by: Jean Delvare <khali@linux-fr.org>
This commit is contained in:
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e313353dd4
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@ -25,8 +25,6 @@ routines, and should be zero-initialized except for fields with data you
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provide. A client structure holds device-specific information like the
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provide. A client structure holds device-specific information like the
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driver model device node, and its I2C address.
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driver model device node, and its I2C address.
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/* iff driver uses driver model ("new style") binding model: */
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static struct i2c_device_id foo_idtable[] = {
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static struct i2c_device_id foo_idtable[] = {
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{ "foo", my_id_for_foo },
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{ "foo", my_id_for_foo },
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{ "bar", my_id_for_bar },
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{ "bar", my_id_for_bar },
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@ -40,7 +38,6 @@ static struct i2c_driver foo_driver = {
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.name = "foo",
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.name = "foo",
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},
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},
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/* iff driver uses driver model ("new style") binding model: */
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.id_table = foo_ids,
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.id_table = foo_ids,
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.probe = foo_probe,
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.probe = foo_probe,
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.remove = foo_remove,
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.remove = foo_remove,
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@ -49,11 +46,6 @@ static struct i2c_driver foo_driver = {
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.detect = foo_detect,
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.detect = foo_detect,
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.address_data = &addr_data,
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.address_data = &addr_data,
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/* else, driver uses "legacy" binding model: */
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.attach_adapter = foo_attach_adapter,
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.detach_client = foo_detach_client,
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/* these may be used regardless of the driver binding model */
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.shutdown = foo_shutdown, /* optional */
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.shutdown = foo_shutdown, /* optional */
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.suspend = foo_suspend, /* optional */
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.suspend = foo_suspend, /* optional */
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.resume = foo_resume, /* optional */
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.resume = foo_resume, /* optional */
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@ -88,7 +80,7 @@ be very useful.
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An example structure is below.
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An example structure is below.
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struct foo_data {
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struct foo_data {
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struct i2c_client client;
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struct i2c_client *client;
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enum chips type; /* To keep the chips type for `sensors' drivers. */
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enum chips type; /* To keep the chips type for `sensors' drivers. */
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/* Because the i2c bus is slow, it is often useful to cache the read
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/* Because the i2c bus is slow, it is often useful to cache the read
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@ -144,10 +136,10 @@ Probing and attaching
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=====================
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=====================
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The Linux I2C stack was originally written to support access to hardware
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The Linux I2C stack was originally written to support access to hardware
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monitoring chips on PC motherboards, and thus it embeds some assumptions
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monitoring chips on PC motherboards, and thus used to embed some assumptions
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that are more appropriate to SMBus (and PCs) than to I2C. One of these
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that were more appropriate to SMBus (and PCs) than to I2C. One of these
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assumptions is that most adapters and devices drivers support the SMBUS_QUICK
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assumptions was that most adapters and devices drivers support the SMBUS_QUICK
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protocol to probe device presence. Another is that devices and their drivers
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protocol to probe device presence. Another was that devices and their drivers
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can be sufficiently configured using only such probe primitives.
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can be sufficiently configured using only such probe primitives.
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As Linux and its I2C stack became more widely used in embedded systems
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As Linux and its I2C stack became more widely used in embedded systems
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@ -164,6 +156,9 @@ since the "legacy" model requires drivers to create "i2c_client" device
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objects after SMBus style probing, while the Linux driver model expects
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objects after SMBus style probing, while the Linux driver model expects
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drivers to be given such device objects in their probe() routines.
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drivers to be given such device objects in their probe() routines.
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The legacy model is deprecated now and will soon be removed, so we no
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longer document it here.
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Standard Driver Model Binding ("New Style")
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Standard Driver Model Binding ("New Style")
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-------------------------------------------
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-------------------------------------------
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@ -193,8 +188,8 @@ matches the device's name. It is passed the entry that was matched so
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the driver knows which one in the table matched.
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the driver knows which one in the table matched.
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Device Creation (Standard driver model)
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Device Creation
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---------------------------------------
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---------------
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If you know for a fact that an I2C device is connected to a given I2C bus,
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If you know for a fact that an I2C device is connected to a given I2C bus,
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you can instantiate that device by simply filling an i2c_board_info
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you can instantiate that device by simply filling an i2c_board_info
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@ -221,8 +216,8 @@ in the I2C bus driver. You may want to save the returned i2c_client
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reference for later use.
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reference for later use.
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Device Detection (Standard driver model)
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Device Detection
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----------------------------------------
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----------------
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Sometimes you do not know in advance which I2C devices are connected to
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Sometimes you do not know in advance which I2C devices are connected to
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a given I2C bus. This is for example the case of hardware monitoring
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a given I2C bus. This is for example the case of hardware monitoring
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@ -246,8 +241,8 @@ otherwise misdetections are likely to occur and things can get wrong
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quickly.
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quickly.
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Device Deletion (Standard driver model)
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Device Deletion
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---------------------------------------
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---------------
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Each I2C device which has been created using i2c_new_device() or
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Each I2C device which has been created using i2c_new_device() or
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i2c_new_probed_device() can be unregistered by calling
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i2c_new_probed_device() can be unregistered by calling
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@ -256,228 +251,6 @@ called automatically before the underlying I2C bus itself is removed, as a
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device can't survive its parent in the device driver model.
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device can't survive its parent in the device driver model.
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Legacy Driver Binding Model
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---------------------------
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Most i2c devices can be present on several i2c addresses; for some this
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is determined in hardware (by soldering some chip pins to Vcc or Ground),
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for others this can be changed in software (by writing to specific client
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registers). Some devices are usually on a specific address, but not always;
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and some are even more tricky. So you will probably need to scan several
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i2c addresses for your clients, and do some sort of detection to see
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whether it is actually a device supported by your driver.
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To give the user a maximum of possibilities, some default module parameters
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are defined to help determine what addresses are scanned. Several macros
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are defined in i2c.h to help you support them, as well as a generic
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detection algorithm.
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You do not have to use this parameter interface; but don't try to use
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function i2c_probe() if you don't.
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Probing classes (Legacy model)
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------------------------------
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All parameters are given as lists of unsigned 16-bit integers. Lists are
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terminated by I2C_CLIENT_END.
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The following lists are used internally:
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normal_i2c: filled in by the module writer.
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A list of I2C addresses which should normally be examined.
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probe: insmod parameter.
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A list of pairs. The first value is a bus number (-1 for any I2C bus),
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the second is the address. These addresses are also probed, as if they
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were in the 'normal' list.
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ignore: insmod parameter.
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A list of pairs. The first value is a bus number (-1 for any I2C bus),
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the second is the I2C address. These addresses are never probed.
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This parameter overrules the 'normal_i2c' list only.
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force: insmod parameter.
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A list of pairs. The first value is a bus number (-1 for any I2C bus),
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the second is the I2C address. A device is blindly assumed to be on
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the given address, no probing is done.
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Additionally, kind-specific force lists may optionally be defined if
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the driver supports several chip kinds. They are grouped in a
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NULL-terminated list of pointers named forces, those first element if the
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generic force list mentioned above. Each additional list correspond to an
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insmod parameter of the form force_<kind>.
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Fortunately, as a module writer, you just have to define the `normal_i2c'
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parameter. The complete declaration could look like this:
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/* Scan 0x4c to 0x4f */
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static const unsigned short normal_i2c[] = { 0x4c, 0x4d, 0x4e, 0x4f,
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I2C_CLIENT_END };
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/* Magic definition of all other variables and things */
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I2C_CLIENT_INSMOD;
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/* Or, if your driver supports, say, 2 kind of devices: */
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I2C_CLIENT_INSMOD_2(foo, bar);
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If you use the multi-kind form, an enum will be defined for you:
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enum chips { any_chip, foo, bar, ... }
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You can then (and certainly should) use it in the driver code.
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Note that you *have* to call the defined variable `normal_i2c',
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without any prefix!
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Attaching to an adapter (Legacy model)
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--------------------------------------
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Whenever a new adapter is inserted, or for all adapters if the driver is
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being registered, the callback attach_adapter() is called. Now is the
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time to determine what devices are present on the adapter, and to register
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a client for each of them.
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The attach_adapter callback is really easy: we just call the generic
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detection function. This function will scan the bus for us, using the
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information as defined in the lists explained above. If a device is
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detected at a specific address, another callback is called.
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int foo_attach_adapter(struct i2c_adapter *adapter)
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{
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return i2c_probe(adapter,&addr_data,&foo_detect_client);
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}
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Remember, structure `addr_data' is defined by the macros explained above,
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so you do not have to define it yourself.
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The i2c_probe function will call the foo_detect_client
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function only for those i2c addresses that actually have a device on
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them (unless a `force' parameter was used). In addition, addresses that
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are already in use (by some other registered client) are skipped.
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The detect client function (Legacy model)
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-----------------------------------------
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The detect client function is called by i2c_probe. The `kind' parameter
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contains -1 for a probed detection, 0 for a forced detection, or a positive
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number for a forced detection with a chip type forced.
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Returning an error different from -ENODEV in a detect function will cause
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the detection to stop: other addresses and adapters won't be scanned.
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This should only be done on fatal or internal errors, such as a memory
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shortage or i2c_attach_client failing.
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For now, you can ignore the `flags' parameter. It is there for future use.
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int foo_detect_client(struct i2c_adapter *adapter, int address,
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int kind)
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{
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int err = 0;
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int i;
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struct i2c_client *client;
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struct foo_data *data;
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const char *name = "";
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/* Let's see whether this adapter can support what we need.
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Please substitute the things you need here! */
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if (!i2c_check_functionality(adapter,I2C_FUNC_SMBUS_WORD_DATA |
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I2C_FUNC_SMBUS_WRITE_BYTE))
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goto ERROR0;
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/* OK. For now, we presume we have a valid client. We now create the
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client structure, even though we cannot fill it completely yet.
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But it allows us to access several i2c functions safely */
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if (!(data = kzalloc(sizeof(struct foo_data), GFP_KERNEL))) {
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err = -ENOMEM;
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goto ERROR0;
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}
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client = &data->client;
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i2c_set_clientdata(client, data);
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client->addr = address;
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client->adapter = adapter;
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client->driver = &foo_driver;
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/* Now, we do the remaining detection. If no `force' parameter is used. */
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/* First, the generic detection (if any), that is skipped if any force
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parameter was used. */
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if (kind < 0) {
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/* The below is of course bogus */
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if (foo_read(client, FOO_REG_GENERIC) != FOO_GENERIC_VALUE)
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goto ERROR1;
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}
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/* Next, specific detection. This is especially important for `sensors'
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devices. */
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/* Determine the chip type. Not needed if a `force_CHIPTYPE' parameter
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was used. */
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if (kind <= 0) {
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i = foo_read(client, FOO_REG_CHIPTYPE);
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if (i == FOO_TYPE_1)
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kind = chip1; /* As defined in the enum */
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else if (i == FOO_TYPE_2)
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kind = chip2;
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else {
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printk("foo: Ignoring 'force' parameter for unknown chip at "
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"adapter %d, address 0x%02x\n",i2c_adapter_id(adapter),address);
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goto ERROR1;
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}
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}
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/* Now set the type and chip names */
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if (kind == chip1) {
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name = "chip1";
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} else if (kind == chip2) {
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name = "chip2";
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}
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/* Fill in the remaining client fields. */
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strlcpy(client->name, name, I2C_NAME_SIZE);
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data->type = kind;
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mutex_init(&data->update_lock); /* Only if you use this field */
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/* Any other initializations in data must be done here too. */
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/* This function can write default values to the client registers, if
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needed. */
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foo_init_client(client);
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/* Tell the i2c layer a new client has arrived */
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if ((err = i2c_attach_client(client)))
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goto ERROR1;
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return 0;
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/* OK, this is not exactly good programming practice, usually. But it is
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very code-efficient in this case. */
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ERROR1:
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kfree(data);
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ERROR0:
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return err;
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}
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Removing the client (Legacy model)
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==================================
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The detach_client call back function is called when a client should be
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removed. It may actually fail, but only when panicking. This code is
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much simpler than the attachment code, fortunately!
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int foo_detach_client(struct i2c_client *client)
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{
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int err;
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/* Try to detach the client from i2c space */
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if ((err = i2c_detach_client(client)))
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return err;
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kfree(i2c_get_clientdata(client));
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return 0;
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}
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Initializing the module or kernel
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Initializing the module or kernel
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=================================
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=================================
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