i2c: Documentation update

Make the documentation on how to write and port i2c drivers more in
line with the current state of things:
* i2c-isa is deprecated and soon gone, so stop advertising it.
* Drop many sensors-specific references. Most of them were outdated
  anyway.
* Update the example code to reflect the recent and not-so-recent
  API and coding style preference changes.
* Simplify the example init and cleanup functions.

This should make things less complex to understand for newcomers.

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

1 files changed, 31 insertions, 261 deletions

diff --git a/Documentation/i2c/writing-clients b/Documentation/i2c/writing-clients
index f7e04ec849b1..3d8d36b0ad12 100644
--- a/Documentation/i2c/writing-clients
+++ b/Documentation/i2c/writing-clients
@@ -74,16 +74,13 @@ An example structure is below.
 
   struct foo_data {
     struct i2c_client client;
-    struct semaphore lock; /* For ISA access in `sensors' drivers. */
-    int sysctl_id;         /* To keep the /proc directory entry for 
-                              `sensors' drivers. */
     enum chips type;       /* To keep the chips type for `sensors' drivers. */
    
     /* Because the i2c bus is slow, it is often useful to cache the read
        information of a chip for some time (for example, 1 or 2 seconds).
        It depends of course on the device whether this is really worthwhile
        or even sensible. */
-    struct semaphore update_lock; /* When we are reading lots of information,
+    struct mutex update_lock;     /* When we are reading lots of information,
                                      another process should not update the
                                      below information */
     char valid;                   /* != 0 if the following fields are valid. */
@@ -104,8 +101,7 @@ some obscure clients). But we need generic reading and writing routines.
 I have found it useful to define foo_read and foo_write function for this.
 For some cases, it will be easier to call the i2c functions directly,
 but many chips have some kind of register-value idea that can easily
-be encapsulated. Also, some chips have both ISA and I2C interfaces, and
-it useful to abstract from this (only for `sensors' drivers).
+be encapsulated.
 
 The below functions are simple examples, and should not be copied
 literally.
@@ -128,24 +124,6 @@ literally.
       return i2c_smbus_write_word_data(client,reg,value);
   }
 
-For sensors code, you may have to cope with ISA registers too. Something
-like the below often works. Note the locking! 
-
-  int foo_read_value(struct i2c_client *client, u8 reg)
-  {
-    int res;
-    if (i2c_is_isa_client(client)) {
-      down(&(((struct foo_data *) (client->data)) -> lock));
-      outb_p(reg,client->addr + FOO_ADDR_REG_OFFSET);
-      res = inb_p(client->addr + FOO_DATA_REG_OFFSET);
-      up(&(((struct foo_data *) (client->data)) -> lock));
-      return res;
-    } else
-      return i2c_smbus_read_byte_data(client,reg);
-  }
-
-Writing is done the same way.
-
 
 Probing and attaching
 =====================
@@ -257,10 +235,6 @@ detection algorithm.
 You do not have to use this parameter interface; but don't try to use
 function i2c_probe() if you don't.
 
-NOTE: If you want to write a `sensors' driver, the interface is slightly
-      different! See below.
-
-
 
 Probing classes (Legacy model)
 ------------------------------
@@ -344,10 +318,6 @@ The detect client function is called by i2c_probe. The `kind' parameter
 contains -1 for a probed detection, 0 for a forced detection, or a positive
 number for a forced detection with a chip type forced.
 
-Below, some things are only needed if this is a `sensors' driver. Those
-parts are between /* SENSORS ONLY START */ and /* SENSORS ONLY END */
-markers. 
-
 Returning an error different from -ENODEV in a detect function will cause
 the detection to stop: other addresses and adapters won't be scanned.
 This should only be done on fatal or internal errors, such as a memory
@@ -356,64 +326,20 @@ shortage or i2c_attach_client failing.
 For now, you can ignore the `flags' parameter. It is there for future use.
 
   int foo_detect_client(struct i2c_adapter *adapter, int address, 
-                        unsigned short flags, int kind)
+                        int kind)
   {
     int err = 0;
     int i;
-    struct i2c_client *new_client;
+    struct i2c_client *client;
     struct foo_data *data;
-    const char *client_name = ""; /* For non-`sensors' drivers, put the real
-                                     name here! */
+    const char *name = "";
    
     /* Let's see whether this adapter can support what we need.
-       Please substitute the things you need here! 
-       For `sensors' drivers, add `! is_isa &&' to the if statement */
+       Please substitute the things you need here! */
     if (!i2c_check_functionality(adapter,I2C_FUNC_SMBUS_WORD_DATA |
                                         I2C_FUNC_SMBUS_WRITE_BYTE))
        goto ERROR0;
 
-    /* SENSORS ONLY START */
-    const char *type_name = "";
-    int is_isa = i2c_is_isa_adapter(adapter);
-
-    /* Do this only if the chip can additionally be found on the ISA bus
-       (hybrid chip). */
-
-    if (is_isa) {
-
-      /* Discard immediately if this ISA range is already used */
-      /* FIXME: never use check_region(), only request_region() */
-      if (check_region(address,FOO_EXTENT))
-        goto ERROR0;
-
-      /* Probe whether there is anything on this address.
-         Some example code is below, but you will have to adapt this
-         for your own driver */
-
-      if (kind < 0) /* Only if no force parameter was used */ {
-        /* We may need long timeouts at least for some chips. */
-        #define REALLY_SLOW_IO
-        i = inb_p(address + 1);
-        if (inb_p(address + 2) != i)
-          goto ERROR0;
-        if (inb_p(address + 3) != i)
-          goto ERROR0;
-        if (inb_p(address + 7) != i)
-          goto ERROR0;
-        #undef REALLY_SLOW_IO
-
-        /* Let's just hope nothing breaks here */
-        i = inb_p(address + 5) & 0x7f;
-        outb_p(~i & 0x7f,address+5);
-        if ((inb_p(address + 5) & 0x7f) != (~i & 0x7f)) {
-          outb_p(i,address+5);
-          return 0;
-        }
-      }
-    }
-
-    /* SENSORS ONLY END */
-
     /* OK. For now, we presume we have a valid client. We now create the
        client structure, even though we cannot fill it completely yet.
        But it allows us to access several i2c functions safely */
@@ -423,13 +349,12 @@ For now, you can ignore the `flags' parameter. It is there for future use.
       goto ERROR0;
     }
 
-    new_client = &data->client;
-    i2c_set_clientdata(new_client, data);
+    client = &data->client;
+    i2c_set_clientdata(client, data);
 
-    new_client->addr = address;
-    new_client->adapter = adapter;
-    new_client->driver = &foo_driver;
-    new_client->flags = 0;
+    client->addr = address;
+    client->adapter = adapter;
+    client->driver = &foo_driver;
 
     /* Now, we do the remaining detection. If no `force' parameter is used. */
 
@@ -437,19 +362,17 @@ For now, you can ignore the `flags' parameter. It is there for future use.
        parameter was used. */
     if (kind < 0) {
       /* The below is of course bogus */
-      if (foo_read(new_client,FOO_REG_GENERIC) != FOO_GENERIC_VALUE)
+      if (foo_read(client, FOO_REG_GENERIC) != FOO_GENERIC_VALUE)
          goto ERROR1;
     }
 
-    /* SENSORS ONLY START */
-
     /* Next, specific detection. This is especially important for `sensors'
        devices. */
 
     /* Determine the chip type. Not needed if a `force_CHIPTYPE' parameter
        was used. */
     if (kind <= 0) {
-      i = foo_read(new_client,FOO_REG_CHIPTYPE);
+      i = foo_read(client, FOO_REG_CHIPTYPE);
       if (i == FOO_TYPE_1) 
         kind = chip1; /* As defined in the enum */
       else if (i == FOO_TYPE_2)
@@ -463,63 +386,31 @@ For now, you can ignore the `flags' parameter. It is there for future use.
 
     /* Now set the type and chip names */
     if (kind == chip1) {
-      type_name = "chip1"; /* For /proc entry */
-      client_name = "CHIP 1";
+      name = "chip1";
     } else if (kind == chip2) {
-      type_name = "chip2"; /* For /proc entry */
-      client_name = "CHIP 2";
+      name = "chip2";
     }
    
-    /* Reserve the ISA region */
-    if (is_isa)
-      request_region(address,FOO_EXTENT,type_name);
-
-    /* SENSORS ONLY END */
-
     /* Fill in the remaining client fields. */
-    strcpy(new_client->name,client_name);
-
-    /* SENSORS ONLY BEGIN */
+    strlcpy(client->name, name, I2C_NAME_SIZE);
     data->type = kind;
-    /* SENSORS ONLY END */
-
-    data->valid = 0; /* Only if you use this field */
-    init_MUTEX(&data->update_lock); /* Only if you use this field */
+    mutex_init(&data->update_lock); /* Only if you use this field */
 
     /* Any other initializations in data must be done here too. */
 
-    /* Tell the i2c layer a new client has arrived */
-    if ((err = i2c_attach_client(new_client)))
-      goto ERROR3;
-
-    /* SENSORS ONLY BEGIN */
-    /* Register a new directory entry with module sensors. See below for
-       the `template' structure. */
-    if ((i = i2c_register_entry(new_client, type_name,
-                                    foo_dir_table_template,THIS_MODULE)) < 0) {
-      err = i;
-      goto ERROR4;
-    }
-    data->sysctl_id = i;
-
-    /* SENSORS ONLY END */
-
     /* This function can write default values to the client registers, if
        needed. */
-    foo_init_client(new_client);
+    foo_init_client(client);
+
+    /* Tell the i2c layer a new client has arrived */
+    if ((err = i2c_attach_client(client)))
+      goto ERROR1;
+
     return 0;
 
     /* OK, this is not exactly good programming practice, usually. But it is
        very code-efficient in this case. */
 
-    ERROR4:
-      i2c_detach_client(new_client);
-    ERROR3:
-    ERROR2:
-    /* SENSORS ONLY START */
-      if (is_isa)
-        release_region(address,FOO_EXTENT);
-    /* SENSORS ONLY END */
     ERROR1:
       kfree(data);
     ERROR0:
@@ -536,22 +427,12 @@ much simpler than the attachment code, fortunately!
 
   int foo_detach_client(struct i2c_client *client)
   {
-    int err,i;
-
-    /* SENSORS ONLY START */
-    /* Deregister with the `i2c-proc' module. */
-    i2c_deregister_entry(((struct lm78_data *)(client->data))->sysctl_id);
-    /* SENSORS ONLY END */
+    int err;
 
     /* Try to detach the client from i2c space */
     if ((err = i2c_detach_client(client)))
       return err;
 
-    /* HYBRID SENSORS CHIP ONLY START */
-    if i2c_is_isa_client(client)
-      release_region(client->addr,LM78_EXTENT);
-    /* HYBRID SENSORS CHIP ONLY END */
-
     kfree(i2c_get_clientdata(client));
     return 0;
   }
@@ -564,42 +445,34 @@ When the kernel is booted, or when your foo driver module is inserted,
 you have to do some initializing. Fortunately, just attaching (registering)
 the driver module is usually enough.
 
-  /* Keep track of how far we got in the initialization process. If several
-     things have to initialized, and we fail halfway, only those things
-     have to be cleaned up! */
-  static int __initdata foo_initialized = 0;
-
   static int __init foo_init(void)
   {
     int res;
-    printk("foo version %s (%s)\n",FOO_VERSION,FOO_DATE);
     
     if ((res = i2c_add_driver(&foo_driver))) {
       printk("foo: Driver registration failed, module not inserted.\n");
-      foo_cleanup();
       return res;
     }
-    foo_initialized ++;
     return 0;
   }
 
-  void foo_cleanup(void)
+  static void __exit foo_cleanup(void)
   {
-    if (foo_initialized == 1) {
-      i2c_del_driver(&foo_driver);
-      foo_initialized --;
-    }
+    i2c_del_driver(&foo_driver);
   }
 
   /* Substitute your own name and email address */
   MODULE_AUTHOR("Frodo Looijaard <frodol@dds.nl>"
   MODULE_DESCRIPTION("Driver for Barf Inc. Foo I2C devices");
 
+  /* a few non-GPL license types are also allowed */
+  MODULE_LICENSE("GPL");
+
   module_init(foo_init);
   module_exit(foo_cleanup);
 
 Note that some functions are marked by `__init', and some data structures
-by `__init_data'.  Hose functions and structures can be removed after
+by `__initdata'.  These functions and structures can be removed after
 kernel booting (or module loading) is completed.
 
 
@@ -729,110 +602,7 @@ General purpose routines
 Below all general purpose routines are listed, that were not mentioned
 before.
 
-  /* This call returns a unique low identifier for each registered adapter,
-   * or -1 if the adapter was not registered.
+  /* This call returns a unique low identifier for each registered adapter.
    */
   extern int i2c_adapter_id(struct i2c_adapter *adap);
 
-
-The sensors sysctl/proc interface
-=================================
-
-This section only applies if you write `sensors' drivers.
-
-Each sensors driver creates a directory in /proc/sys/dev/sensors for each
-registered client. The directory is called something like foo-i2c-4-65.
-The sensors module helps you to do this as easily as possible.
-
-The template
-------------
-
-You will need to define a ctl_table template. This template will automatically
-be copied to a newly allocated structure and filled in where necessary when
-you call sensors_register_entry.
-
-First, I will give an example definition.
-  static ctl_table foo_dir_table_template[] = {
-    { FOO_SYSCTL_FUNC1, "func1", NULL, 0, 0644, NULL, &i2c_proc_real,
-      &i2c_sysctl_real,NULL,&foo_func },
-    { FOO_SYSCTL_FUNC2, "func2", NULL, 0, 0644, NULL, &i2c_proc_real,
-      &i2c_sysctl_real,NULL,&foo_func },
-    { FOO_SYSCTL_DATA, "data", NULL, 0, 0644, NULL, &i2c_proc_real,
-      &i2c_sysctl_real,NULL,&foo_data },
-    { 0 }
-  };
-
-In the above example, three entries are defined. They can either be
-accessed through the /proc interface, in the /proc/sys/dev/sensors/*
-directories, as files named func1, func2 and data, or alternatively 
-through the sysctl interface, in the appropriate table, with identifiers
-FOO_SYSCTL_FUNC1, FOO_SYSCTL_FUNC2 and FOO_SYSCTL_DATA.
-
-The third, sixth and ninth parameters should always be NULL, and the
-fourth should always be 0. The fifth is the mode of the /proc file;
-0644 is safe, as the file will be owned by root:root. 
-
-The seventh and eighth parameters should be &i2c_proc_real and
-&i2c_sysctl_real if you want to export lists of reals (scaled
-integers). You can also use your own function for them, as usual.
-Finally, the last parameter is the call-back to gather the data
-(see below) if you use the *_proc_real functions. 
-
-
-Gathering the data
-------------------
-
-The call back functions (foo_func and foo_data in the above example)
-can be called in several ways; the operation parameter determines
-what should be done:
-
-  * If operation == SENSORS_PROC_REAL_INFO, you must return the
-    magnitude (scaling) in nrels_mag;
-  * If operation == SENSORS_PROC_REAL_READ, you must read information
-    from the chip and return it in results. The number of integers
-    to display should be put in nrels_mag;
-  * If operation == SENSORS_PROC_REAL_WRITE, you must write the
-    supplied information to the chip. nrels_mag will contain the number
-    of integers, results the integers themselves.
-
-The *_proc_real functions will display the elements as reals for the
-/proc interface. If you set the magnitude to 2, and supply 345 for
-SENSORS_PROC_REAL_READ, it would display 3.45; and if the user would
-write 45.6 to the /proc file, it would be returned as 4560 for
-SENSORS_PROC_REAL_WRITE. A magnitude may even be negative!
-
-An example function:
-
-  /* FOO_FROM_REG and FOO_TO_REG translate between scaled values and
-     register values. Note the use of the read cache. */
-  void foo_in(struct i2c_client *client, int operation, int ctl_name, 
-              int *nrels_mag, long *results)
-  {
-    struct foo_data *data = client->data;
-    int nr = ctl_name - FOO_SYSCTL_FUNC1; /* reduce to 0 upwards */
-    
-    if (operation == SENSORS_PROC_REAL_INFO)
-      *nrels_mag = 2;
-    else if (operation == SENSORS_PROC_REAL_READ) {
-      /* Update the readings cache (if necessary) */
-      foo_update_client(client);
-      /* Get the readings from the cache */
-      results[0] = FOO_FROM_REG(data->foo_func_base[nr]);
-      results[1] = FOO_FROM_REG(data->foo_func_more[nr]);
-      results[2] = FOO_FROM_REG(data->foo_func_readonly[nr]);
-      *nrels_mag = 2;
-    } else if (operation == SENSORS_PROC_REAL_WRITE) {
-      if (*nrels_mag >= 1) {
-        /* Update the cache */
-        data->foo_base[nr] = FOO_TO_REG(results[0]);
-        /* Update the chip */
-        foo_write_value(client,FOO_REG_FUNC_BASE(nr),data->foo_base[nr]);
-      }
-      if (*nrels_mag >= 2) {
-        /* Update the cache */
-        data->foo_more[nr] = FOO_TO_REG(results[1]);
-        /* Update the chip */
-        foo_write_value(client,FOO_REG_FUNC_MORE(nr),data->foo_more[nr]);
-      }
-    }
-  }