[PATCH] w1: Added default generic read/write operations.

Special file in each w1 slave device's directory called "rw" is created
each time new slave and no appropriate w1 family is registered.
"rw" file supports read and write operations, which allows to perform
almost any kind of operations. Each logical operation is a transaction
in nature, which can contain several (two or one) low-level operations.
Let's see how one can read EEPROM context:
1. one must write control buffer, i.e. buffer containing command byte
and two byte address. At this step bus is reset and appropriate device
is selected using either W1_SKIP_ROM or W1_MATCH_ROM command.
Then provided control buffer is being written to the wire.
2. reading. This will issue reading eeprom response.

It is possible that between 1. and 2. w1 master thread will reset bus for
searching and slave device will be even removed, but in this case 0xff will
be read, since no device was selected.

Signed-off-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 15 insertions, 3 deletions

diff --git a/Documentation/w1/w1.generic b/Documentation/w1/w1.generic
index f937fbe1cacb..4c6509dd4789 100644
--- a/Documentation/w1/w1.generic
+++ b/Documentation/w1/w1.generic
@@ -27,8 +27,19 @@ When a w1 master driver registers with the w1 subsystem, the following occurs:
 
 When a device is found on the bus, w1 core checks if driver for it's family is
 loaded. If so, the family driver is attached to the slave.
-If there is no driver for the family, a simple sysfs entry is created
-for the slave device.
+If there is no driver for the family, default one is assigned, which allows to perform
+almost any kind of operations. Each logical operation is a transaction
+in nature, which can contain several (two or one) low-level operations.
+Let's see how one can read EEPROM context:
+1. one must write control buffer, i.e. buffer containing command byte
+and two byte address. At this step bus is reset and appropriate device
+is selected using either W1_SKIP_ROM or W1_MATCH_ROM command.
+Then provided control buffer is being written to the wire.
+2. reading. This will issue reading eeprom response.
+
+It is possible that between 1. and 2. w1 master thread will reset bus for searching
+and slave device will be even removed, but in this case 0xff will
+be read, since no device was selected.
 
 
 W1 device families
@@ -89,4 +100,5 @@ driver             - (standard) symlink to the w1 driver
 name               - the device name, usually the same as the directory name
 w1_slave           - (optional) a binary file whose meaning depends on the
                      family driver
-
+rw                 - (optional) created for slave devices which do not have
+                     appropriate family driver. Allows to read/write binary data.