summaryrefslogtreecommitdiffstats
path: root/Documentation/i2c
diff options
context:
space:
mode:
Diffstat (limited to 'Documentation/i2c')
-rw-r--r--Documentation/i2c/busses/i2c-i81047
-rw-r--r--Documentation/i2c/busses/i2c-prosavage23
-rw-r--r--Documentation/i2c/busses/i2c-savage426
-rw-r--r--Documentation/i2c/chips/max68752
-rw-r--r--Documentation/i2c/chips/pca953910
-rw-r--r--Documentation/i2c/chips/pcf857412
-rw-r--r--Documentation/i2c/chips/pcf85759
-rw-r--r--Documentation/i2c/fault-codes127
-rw-r--r--Documentation/i2c/smbus-protocol4
-rw-r--r--Documentation/i2c/writing-clients51
10 files changed, 187 insertions, 124 deletions
diff --git a/Documentation/i2c/busses/i2c-i810 b/Documentation/i2c/busses/i2c-i810
deleted file mode 100644
index 778210ee158..00000000000
--- a/Documentation/i2c/busses/i2c-i810
+++ /dev/null
@@ -1,47 +0,0 @@
-Kernel driver i2c-i810
-
-Supported adapters:
- * Intel 82810, 82810-DC100, 82810E, and 82815 (GMCH)
- * Intel 82845G (GMCH)
-
-Authors:
- Frodo Looijaard <frodol@dds.nl>,
- Philip Edelbrock <phil@netroedge.com>,
- Kyösti Mälkki <kmalkki@cc.hut.fi>,
- Ralph Metzler <rjkm@thp.uni-koeln.de>,
- Mark D. Studebaker <mdsxyz123@yahoo.com>
-
-Main contact: Mark Studebaker <mdsxyz123@yahoo.com>
-
-Description
------------
-
-WARNING: If you have an '810' or '815' motherboard, your standard I2C
-temperature sensors are most likely on the 801's I2C bus. You want the
-i2c-i801 driver for those, not this driver.
-
-Now for the i2c-i810...
-
-The GMCH chip contains two I2C interfaces.
-
-The first interface is used for DDC (Data Display Channel) which is a
-serial channel through the VGA monitor connector to a DDC-compliant
-monitor. This interface is defined by the Video Electronics Standards
-Association (VESA). The standards are available for purchase at
-http://www.vesa.org .
-
-The second interface is a general-purpose I2C bus. It may be connected to a
-TV-out chip such as the BT869 or possibly to a digital flat-panel display.
-
-Features
---------
-
-Both busses use the i2c-algo-bit driver for 'bit banging'
-and support for specific transactions is provided by i2c-algo-bit.
-
-Issues
-------
-
-If you enable bus testing in i2c-algo-bit (insmod i2c-algo-bit bit_test=1),
-the test may fail; if so, the i2c-i810 driver won't be inserted. However,
-we think this has been fixed.
diff --git a/Documentation/i2c/busses/i2c-prosavage b/Documentation/i2c/busses/i2c-prosavage
deleted file mode 100644
index 70368790251..00000000000
--- a/Documentation/i2c/busses/i2c-prosavage
+++ /dev/null
@@ -1,23 +0,0 @@
-Kernel driver i2c-prosavage
-
-Supported adapters:
-
- S3/VIA KM266/VT8375 aka ProSavage8
- S3/VIA KM133/VT8365 aka Savage4
-
-Author: Henk Vergonet <henk@god.dyndns.org>
-
-Description
------------
-
-The Savage4 chips contain two I2C interfaces (aka a I2C 'master' or
-'host').
-
-The first interface is used for DDC (Data Display Channel) which is a
-serial channel through the VGA monitor connector to a DDC-compliant
-monitor. This interface is defined by the Video Electronics Standards
-Association (VESA). The standards are available for purchase at
-http://www.vesa.org . The second interface is a general-purpose I2C bus.
-
-Usefull for gaining access to the TV Encoder chips.
-
diff --git a/Documentation/i2c/busses/i2c-savage4 b/Documentation/i2c/busses/i2c-savage4
deleted file mode 100644
index 6ecceab618d..00000000000
--- a/Documentation/i2c/busses/i2c-savage4
+++ /dev/null
@@ -1,26 +0,0 @@
-Kernel driver i2c-savage4
-
-Supported adapters:
- * Savage4
- * Savage2000
-
-Authors:
- Alexander Wold <awold@bigfoot.com>,
- Mark D. Studebaker <mdsxyz123@yahoo.com>
-
-Description
------------
-
-The Savage4 chips contain two I2C interfaces (aka a I2C 'master'
-or 'host').
-
-The first interface is used for DDC (Data Display Channel) which is a
-serial channel through the VGA monitor connector to a DDC-compliant
-monitor. This interface is defined by the Video Electronics Standards
-Association (VESA). The standards are available for purchase at
-http://www.vesa.org . The DDC bus is not yet supported because its register
-is not directly memory-mapped.
-
-The second interface is a general-purpose I2C bus. This is the only
-interface supported by the driver at the moment.
-
diff --git a/Documentation/i2c/chips/max6875 b/Documentation/i2c/chips/max6875
index a0cd8af2f40..10ca43cd1a7 100644
--- a/Documentation/i2c/chips/max6875
+++ b/Documentation/i2c/chips/max6875
@@ -49,7 +49,7 @@ $ modprobe max6875 force=0,0x50
The MAX6874/MAX6875 ignores address bit 0, so this driver attaches to multiple
addresses. For example, for address 0x50, it also reserves 0x51.
-The even-address instance is called 'max6875', the odd one is 'max6875 subclient'.
+The even-address instance is called 'max6875', the odd one is 'dummy'.
Programming the chip using i2c-dev
diff --git a/Documentation/i2c/chips/pca9539 b/Documentation/i2c/chips/pca9539
index 1d81c530c4a..6aff890088b 100644
--- a/Documentation/i2c/chips/pca9539
+++ b/Documentation/i2c/chips/pca9539
@@ -7,7 +7,7 @@ drivers/gpio/pca9539.c instead.
Supported chips:
* Philips PCA9539
Prefix: 'pca9539'
- Addresses scanned: 0x74 - 0x77
+ Addresses scanned: none
Datasheet:
http://www.semiconductors.philips.com/acrobat/datasheets/PCA9539_2.pdf
@@ -23,6 +23,14 @@ The input sense can also be inverted.
The 16 lines are split between two bytes.
+Detection
+---------
+
+The PCA9539 is difficult to detect and not commonly found in PC machines,
+so you have to pass the I2C bus and address of the installed PCA9539
+devices explicitly to the driver at load time via the force=... parameter.
+
+
Sysfs entries
-------------
diff --git a/Documentation/i2c/chips/pcf8574 b/Documentation/i2c/chips/pcf8574
index 5c1ad1376b6..235815c075f 100644
--- a/Documentation/i2c/chips/pcf8574
+++ b/Documentation/i2c/chips/pcf8574
@@ -4,13 +4,13 @@ Kernel driver pcf8574
Supported chips:
* Philips PCF8574
Prefix: 'pcf8574'
- Addresses scanned: I2C 0x20 - 0x27
+ Addresses scanned: none
Datasheet: Publicly available at the Philips Semiconductors website
http://www.semiconductors.philips.com/pip/PCF8574P.html
* Philips PCF8574A
Prefix: 'pcf8574a'
- Addresses scanned: I2C 0x38 - 0x3f
+ Addresses scanned: none
Datasheet: Publicly available at the Philips Semiconductors website
http://www.semiconductors.philips.com/pip/PCF8574P.html
@@ -38,12 +38,10 @@ For more informations see the datasheet.
Accessing PCF8574(A) via /sys interface
-------------------------------------
-! Be careful !
The PCF8574(A) is plainly impossible to detect ! Stupid chip.
-So every chip with address in the interval [20..27] and [38..3f] are
-detected as PCF8574(A). If you have other chips in this address
-range, the workaround is to load this module after the one
-for your others chips.
+So, you have to pass the I2C bus and address of the installed PCF857A
+and PCF8574A devices explicitly to the driver at load time via the
+force=... parameter.
On detection (i.e. insmod, modprobe et al.), directories are being
created for each detected PCF8574(A):
diff --git a/Documentation/i2c/chips/pcf8575 b/Documentation/i2c/chips/pcf8575
index 25f5698a61c..40b268eb276 100644
--- a/Documentation/i2c/chips/pcf8575
+++ b/Documentation/i2c/chips/pcf8575
@@ -40,12 +40,9 @@ Detection
---------
There is no method known to detect whether a chip on a given I2C address is
-a PCF8575 or whether it is any other I2C device. So there are two alternatives
-to let the driver find the installed PCF8575 devices:
-- Load this driver after any other I2C driver for I2C devices with addresses
- in the range 0x20 .. 0x27.
-- Pass the I2C bus and address of the installed PCF8575 devices explicitly to
- the driver at load time via the probe=... or force=... parameters.
+a PCF8575 or whether it is any other I2C device, so you have to pass the I2C
+bus and address of the installed PCF8575 devices explicitly to the driver at
+load time via the force=... parameter.
/sys interface
--------------
diff --git a/Documentation/i2c/fault-codes b/Documentation/i2c/fault-codes
new file mode 100644
index 00000000000..045765c0b9b
--- /dev/null
+++ b/Documentation/i2c/fault-codes
@@ -0,0 +1,127 @@
+This is a summary of the most important conventions for use of fault
+codes in the I2C/SMBus stack.
+
+
+A "Fault" is not always an "Error"
+----------------------------------
+Not all fault reports imply errors; "page faults" should be a familiar
+example. Software often retries idempotent operations after transient
+faults. There may be fancier recovery schemes that are appropriate in
+some cases, such as re-initializing (and maybe resetting). After such
+recovery, triggered by a fault report, there is no error.
+
+In a similar way, sometimes a "fault" code just reports one defined
+result for an operation ... it doesn't indicate that anything is wrong
+at all, just that the outcome wasn't on the "golden path".
+
+In short, your I2C driver code may need to know these codes in order
+to respond correctly. Other code may need to rely on YOUR code reporting
+the right fault code, so that it can (in turn) behave correctly.
+
+
+I2C and SMBus fault codes
+-------------------------
+These are returned as negative numbers from most calls, with zero or
+some positive number indicating a non-fault return. The specific
+numbers associated with these symbols differ between architectures,
+though most Linux systems use <asm-generic/errno*.h> numbering.
+
+Note that the descriptions here are not exhaustive. There are other
+codes that may be returned, and other cases where these codes should
+be returned. However, drivers should not return other codes for these
+cases (unless the hardware doesn't provide unique fault reports).
+
+Also, codes returned by adapter probe methods follow rules which are
+specific to their host bus (such as PCI, or the platform bus).
+
+
+EAGAIN
+ Returned by I2C adapters when they lose arbitration in master
+ transmit mode: some other master was transmitting different
+ data at the same time.
+
+ Also returned when trying to invoke an I2C operation in an
+ atomic context, when some task is already using that I2C bus
+ to execute some other operation.
+
+EBADMSG
+ Returned by SMBus logic when an invalid Packet Error Code byte
+ is received. This code is a CRC covering all bytes in the
+ transaction, and is sent before the terminating STOP. This
+ fault is only reported on read transactions; the SMBus slave
+ may have a way to report PEC mismatches on writes from the
+ host. Note that even if PECs are in use, you should not rely
+ on these as the only way to detect incorrect data transfers.
+
+EBUSY
+ Returned by SMBus adapters when the bus was busy for longer
+ than allowed. This usually indicates some device (maybe the
+ SMBus adapter) needs some fault recovery (such as resetting),
+ or that the reset was attempted but failed.
+
+EINVAL
+ This rather vague error means an invalid parameter has been
+ detected before any I/O operation was started. Use a more
+ specific fault code when you can.
+
+ One example would be a driver trying an SMBus Block Write
+ with block size outside the range of 1-32 bytes.
+
+EIO
+ This rather vague error means something went wrong when
+ performing an I/O operation. Use a more specific fault
+ code when you can.
+
+ENODEV
+ Returned by driver probe() methods. This is a bit more
+ specific than ENXIO, implying the problem isn't with the
+ address, but with the device found there. Driver probes
+ may verify the device returns *correct* responses, and
+ return this as appropriate. (The driver core will warn
+ about probe faults other than ENXIO and ENODEV.)
+
+ENOMEM
+ Returned by any component that can't allocate memory when
+ it needs to do so.
+
+ENXIO
+ Returned by I2C adapters to indicate that the address phase
+ of a transfer didn't get an ACK. While it might just mean
+ an I2C device was temporarily not responding, usually it
+ means there's nothing listening at that address.
+
+ Returned by driver probe() methods to indicate that they
+ found no device to bind to. (ENODEV may also be used.)
+
+EOPNOTSUPP
+ Returned by an adapter when asked to perform an operation
+ that it doesn't, or can't, support.
+
+ For example, this would be returned when an adapter that
+ doesn't support SMBus block transfers is asked to execute
+ one. In that case, the driver making that request should
+ have verified that functionality was supported before it
+ made that block transfer request.
+
+ Similarly, if an I2C adapter can't execute all legal I2C
+ messages, it should return this when asked to perform a
+ transaction it can't. (These limitations can't be seen in
+ the adapter's functionality mask, since the assumption is
+ that if an adapter supports I2C it supports all of I2C.)
+
+EPROTO
+ Returned when slave does not conform to the relevant I2C
+ or SMBus (or chip-specific) protocol specifications. One
+ case is when the length of an SMBus block data response
+ (from the SMBus slave) is outside the range 1-32 bytes.
+
+ETIMEDOUT
+ This is returned by drivers when an operation took too much
+ time, and was aborted before it completed.
+
+ SMBus adapters may return it when an operation took more
+ time than allowed by the SMBus specification; for example,
+ when a slave stretches clocks too far. I2C has no such
+ timeouts, but it's normal for I2C adapters to impose some
+ arbitrary limits (much longer than SMBus!) too.
+
diff --git a/Documentation/i2c/smbus-protocol b/Documentation/i2c/smbus-protocol
index 03f08fb491c..24bfb65da17 100644
--- a/Documentation/i2c/smbus-protocol
+++ b/Documentation/i2c/smbus-protocol
@@ -42,8 +42,8 @@ Count (8 bits): A data byte containing the length of a block operation.
[..]: Data sent by I2C device, as opposed to data sent by the host adapter.
-SMBus Quick Command: i2c_smbus_write_quick()
-=============================================
+SMBus Quick Command
+===================
This sends a single bit to the device, at the place of the Rd/Wr bit.
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.