diff options
Diffstat (limited to 'Documentation/i2c')
| -rw-r--r-- | Documentation/i2c/busses/i2c-i810 | 47 | ||||
| -rw-r--r-- | Documentation/i2c/busses/i2c-prosavage | 23 | ||||
| -rw-r--r-- | Documentation/i2c/busses/i2c-savage4 | 26 | ||||
| -rw-r--r-- | Documentation/i2c/chips/max6875 | 2 | ||||
| -rw-r--r-- | Documentation/i2c/chips/pca9539 | 10 | ||||
| -rw-r--r-- | Documentation/i2c/chips/pcf8574 | 12 | ||||
| -rw-r--r-- | Documentation/i2c/chips/pcf8575 | 9 | ||||
| -rw-r--r-- | Documentation/i2c/fault-codes | 127 | ||||
| -rw-r--r-- | Documentation/i2c/functionality | 95 | ||||
| -rw-r--r-- | Documentation/i2c/smbus-protocol | 81 | ||||
| -rw-r--r-- | Documentation/i2c/upgrading-clients | 281 | ||||
| -rw-r--r-- | Documentation/i2c/writing-clients | 69 |
12 files changed, 578 insertions, 204 deletions
diff --git a/Documentation/i2c/busses/i2c-i810 b/Documentation/i2c/busses/i2c-i810 deleted file mode 100644 index 778210ee1583..000000000000 --- 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 703687902511..000000000000 --- 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 6ecceab618d3..000000000000 --- 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 a0cd8af2f408..10ca43cd1a72 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 1d81c530c4a5..6aff890088b1 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 5c1ad1376b62..235815c075ff 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 25f5698a61cf..40b268eb276f 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 000000000000..045765c0b9b5 --- /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/functionality b/Documentation/i2c/functionality index 60cca249e452..42c17c1fb3cd 100644 --- a/Documentation/i2c/functionality +++ b/Documentation/i2c/functionality @@ -51,26 +51,38 @@ A few combinations of the above flags are also defined for your convenience: the transparent emulation layer) -ALGORITHM/ADAPTER IMPLEMENTATION --------------------------------- +ADAPTER IMPLEMENTATION +---------------------- -When you write a new algorithm driver, you will have to implement a -function callback `functionality', that gets an i2c_adapter structure -pointer as its only parameter: +When you write a new adapter driver, you will have to implement a +function callback `functionality'. Typical implementations are given +below. - struct i2c_algorithm { - /* Many other things of course; check <linux/i2c.h>! */ - u32 (*functionality) (struct i2c_adapter *); +A typical SMBus-only adapter would list all the SMBus transactions it +supports. This example comes from the i2c-piix4 driver: + + static u32 piix4_func(struct i2c_adapter *adapter) + { + return I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE | + I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA | + I2C_FUNC_SMBUS_BLOCK_DATA; } -A typically implementation is given below, from i2c-algo-bit.c: +A typical full-I2C adapter would use the following (from the i2c-pxa +driver): - static u32 bit_func(struct i2c_adapter *adap) + static u32 i2c_pxa_functionality(struct i2c_adapter *adap) { - return I2C_FUNC_SMBUS_EMUL | I2C_FUNC_10BIT_ADDR | - I2C_FUNC_PROTOCOL_MANGLING; + return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL; } +I2C_FUNC_SMBUS_EMUL includes all the SMBus transactions (with the +addition of I2C block transactions) which i2c-core can emulate using +I2C_FUNC_I2C without any help from the adapter driver. The idea is +to let the client drivers check for the support of SMBus functions +without having to care whether the said functions are implemented in +hardware by the adapter, or emulated in software by i2c-core on top +of an I2C adapter. CLIENT CHECKING @@ -78,36 +90,33 @@ CLIENT CHECKING Before a client tries to attach to an adapter, or even do tests to check whether one of the devices it supports is present on an adapter, it should -check whether the needed functionality is present. There are two functions -defined which should be used instead of calling the functionality hook -in the algorithm structure directly: - - /* Return the functionality mask */ - extern u32 i2c_get_functionality (struct i2c_adapter *adap); - - /* Return 1 if adapter supports everything we need, 0 if not. */ - extern int i2c_check_functionality (struct i2c_adapter *adap, u32 func); +check whether the needed functionality is present. The typical way to do +this is (from the lm75 driver): -This is a typical way to use these functions (from the writing-clients -document): - int foo_detect_client(struct i2c_adapter *adapter, int address, - unsigned short flags, int kind) + static int lm75_detect(...) { - /* Define needed variables */ - - /* As the very first action, we check whether the adapter has the - needed functionality: we need the SMBus read_word_data, - write_word_data and write_byte functions in this example. */ - if (!i2c_check_functionality(adapter,I2C_FUNC_SMBUS_WORD_DATA | - I2C_FUNC_SMBUS_WRITE_BYTE)) - goto ERROR0; - - /* Now we can do the real detection */ - - ERROR0: - /* Return an error */ + (...) + if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA | + I2C_FUNC_SMBUS_WORD_DATA)) + goto exit; + (...) } +Here, the lm75 driver checks if the adapter can do both SMBus byte data +and SMBus word data transactions. If not, then the driver won't work on +this adapter and there's no point in going on. If the check above is +successful, then the driver knows that it can call the following +functions: i2c_smbus_read_byte_data(), i2c_smbus_write_byte_data(), +i2c_smbus_read_word_data() and i2c_smbus_write_word_data(). As a rule of +thumb, the functionality constants you test for with +i2c_check_functionality() should match exactly the i2c_smbus_* functions +which you driver is calling. + +Note that the check above doesn't tell whether the functionalities are +implemented in hardware by the underlying adapter or emulated in +software by i2c-core. Client drivers don't have to care about this, as +i2c-core will transparently implement SMBus transactions on top of I2C +adapters. CHECKING THROUGH /DEV @@ -116,19 +125,19 @@ CHECKING THROUGH /DEV If you try to access an adapter from a userspace program, you will have to use the /dev interface. You will still have to check whether the functionality you need is supported, of course. This is done using -the I2C_FUNCS ioctl. An example, adapted from the lm_sensors i2cdetect -program, is below: +the I2C_FUNCS ioctl. An example, adapted from the i2cdetect program, is +below: int file; - if (file = open("/dev/i2c-0",O_RDWR) < 0) { + if (file = open("/dev/i2c-0", O_RDWR) < 0) { /* Some kind of error handling */ exit(1); } - if (ioctl(file,I2C_FUNCS,&funcs) < 0) { + if (ioctl(file, I2C_FUNCS, &funcs) < 0) { /* Some kind of error handling */ exit(1); } - if (! (funcs & I2C_FUNC_SMBUS_QUICK)) { + if (!(funcs & I2C_FUNC_SMBUS_QUICK)) { /* Oops, the needed functionality (SMBus write_quick function) is not available! */ exit(1); diff --git a/Documentation/i2c/smbus-protocol b/Documentation/i2c/smbus-protocol index 8a653c60d25a..24bfb65da17d 100644 --- a/Documentation/i2c/smbus-protocol +++ b/Documentation/i2c/smbus-protocol @@ -1,5 +1,6 @@ SMBus Protocol Summary ====================== + The following is a summary of the SMBus protocol. It applies to all revisions of the protocol (1.0, 1.1, and 2.0). Certain protocol features which are not supported by @@ -8,6 +9,7 @@ this package are briefly described at the end of this document. Some adapters understand only the SMBus (System Management Bus) protocol, which is a subset from the I2C protocol. Fortunately, many devices use only the same subset, which makes it possible to put them on an SMBus. + If you write a driver for some I2C device, please try to use the SMBus commands if at all possible (if the device uses only that subset of the I2C protocol). This makes it possible to use the device driver on both @@ -15,7 +17,12 @@ SMBus adapters and I2C adapters (the SMBus command set is automatically translated to I2C on I2C adapters, but plain I2C commands can not be handled at all on most pure SMBus adapters). -Below is a list of SMBus commands. +Below is a list of SMBus protocol operations, and the functions executing +them. Note that the names used in the SMBus protocol specifications usually +don't match these function names. For some of the operations which pass a +single data byte, the functions using SMBus protocol operation names execute +a different protocol operation entirely. + Key to symbols ============== @@ -35,17 +42,16 @@ 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 Write Quick -================= +SMBus Quick Command +=================== This sends a single bit to the device, at the place of the Rd/Wr bit. -There is no equivalent Read Quick command. A Addr Rd/Wr [A] P -SMBus Read Byte -=============== +SMBus Receive Byte: i2c_smbus_read_byte() +========================================== This reads a single byte from a device, without specifying a device register. Some devices are so simple that this interface is enough; for @@ -55,17 +61,17 @@ the previous SMBus command. S Addr Rd [A] [Data] NA P -SMBus Write Byte -================ +SMBus Send Byte: i2c_smbus_write_byte() +======================================== -This is the reverse of Read Byte: it sends a single byte to a device. -See Read Byte for more information. +This operation is the reverse of Receive Byte: it sends a single byte +to a device. See Receive Byte for more information. S Addr Wr [A] Data [A] P -SMBus Read Byte Data -==================== +SMBus Read Byte: i2c_smbus_read_byte_data() +============================================ This reads a single byte from a device, from a designated register. The register is specified through the Comm byte. @@ -73,30 +79,30 @@ The register is specified through the Comm byte. S Addr Wr [A] Comm [A] S Addr Rd [A] [Data] NA P -SMBus Read Word Data -==================== +SMBus Read Word: i2c_smbus_read_word_data() +============================================ -This command is very like Read Byte Data; again, data is read from a +This operation is very like Read Byte; again, data is read from a device, from a designated register that is specified through the Comm byte. But this time, the data is a complete word (16 bits). S Addr Wr [A] Comm [A] S Addr Rd [A] [DataLow] A [DataHigh] NA P -SMBus Write Byte Data -===================== +SMBus Write Byte: i2c_smbus_write_byte_data() +============================================== This writes a single byte to a device, to a designated register. The register is specified through the Comm byte. This is the opposite of -the Read Byte Data command. +the Read Byte operation. S Addr Wr [A] Comm [A] Data [A] P -SMBus Write Word Data -===================== +SMBus Write Word: i2c_smbus_write_word_data() +============================================== -This is the opposite operation of the Read Word Data command. 16 bits +This is the opposite of the Read Word operation. 16 bits of data is written to a device, to the designated register that is specified through the Comm byte. @@ -113,8 +119,8 @@ S Addr Wr [A] Comm [A] DataLow [A] DataHigh [A] S Addr Rd [A] [DataLow] A [DataHigh] NA P -SMBus Block Read -================ +SMBus Block Read: i2c_smbus_read_block_data() +============================================== This command reads a block of up to 32 bytes from a device, from a designated register that is specified through the Comm byte. The amount @@ -124,8 +130,8 @@ S Addr Wr [A] Comm [A] S Addr Rd [A] [Count] A [Data] A [Data] A ... A [Data] NA P -SMBus Block Write -================= +SMBus Block Write: i2c_smbus_write_block_data() +================================================ The opposite of the Block Read command, this writes up to 32 bytes to a device, to a designated register that is specified through the @@ -134,10 +140,11 @@ Comm byte. The amount of data is specified in the Count byte. S Addr Wr [A] Comm [A] Count [A] Data [A] Data [A] ... [A] Data [A] P -SMBus Block Process Call -======================== +SMBus Block Write - Block Read Process Call +=========================================== -SMBus Block Process Call was introduced in Revision 2.0 of the specification. +SMBus Block Write - Block Read Process Call was introduced in +Revision 2.0 of the specification. This command selects a device register (through the Comm byte), sends 1 to 31 bytes of data to it, and reads 1 to 31 bytes of data in return. @@ -159,13 +166,16 @@ alerting device's address. Packet Error Checking (PEC) =========================== + Packet Error Checking was introduced in Revision 1.1 of the specification. -PEC adds a CRC-8 error-checking byte to all transfers. +PEC adds a CRC-8 error-checking byte to transfers using it, immediately +before the terminating STOP. Address Resolution Protocol (ARP) ================================= + The Address Resolution Protocol was introduced in Revision 2.0 of the specification. It is a higher-layer protocol which uses the messages above. @@ -177,14 +187,17 @@ require PEC checksums. I2C Block Transactions ====================== + The following I2C block transactions are supported by the SMBus layer and are described here for completeness. +They are *NOT* defined by the SMBus specification. + I2C block transactions do not limit the number of bytes transferred but the SMBus layer places a limit of 32 bytes. -I2C Block Read -============== +I2C Block Read: i2c_smbus_read_i2c_block_data() +================================================ This command reads a block of bytes from a device, from a designated register that is specified through the Comm byte. @@ -203,8 +216,8 @@ S Addr Wr [A] Comm1 [A] Comm2 [A] S Addr Rd [A] [Data] A [Data] A ... A [Data] NA P -I2C Block Write -=============== +I2C Block Write: i2c_smbus_write_i2c_block_data() +================================================== The opposite of the Block Read command, this writes bytes to a device, to a designated register that is specified through the @@ -212,5 +225,3 @@ Comm byte. Note that command lengths of 0, 2, or more bytes are supported as they are indistinguishable from data. S Addr Wr [A] Comm [A] Data [A] Data [A] ... [A] Data [A] P - - diff --git a/Documentation/i2c/upgrading-clients b/Documentation/i2c/upgrading-clients new file mode 100644 index 000000000000..9a45f9bb6a25 --- /dev/null +++ b/Documentation/i2c/upgrading-clients @@ -0,0 +1,281 @@ +Upgrading I2C Drivers to the new 2.6 Driver Model +================================================= + +Ben Dooks <ben-linux@fluff.org> + +Introduction +------------ + +This guide outlines how to alter existing Linux 2.6 client drivers from +the old to the new new binding methods. + + +Example old-style driver +------------------------ + + +struct example_state { + struct i2c_client client; + .... +}; + +static struct i2c_driver example_driver; + +static unsigned short ignore[] = { I2C_CLIENT_END }; +static unsigned short normal_addr[] = { OUR_ADDR, I2C_CLIENT_END }; + +I2C_CLIENT_INSMOD; + +static int example_attach(struct i2c_adapter *adap, int addr, int kind) +{ + struct example_state *state; + struct device *dev = &adap->dev; /* to use for dev_ reports */ + int ret; + + state = kzalloc(sizeof(struct example_state), GFP_KERNEL); + if (state == NULL) { + dev_err(dev, "failed to create our state\n"); + return -ENOMEM; + } + + example->client.addr = addr; + example->client.flags = 0; + example->client.adapter = adap; + + i2c_set_clientdata(&state->i2c_client, state); + strlcpy(client->i2c_client.name, "example", I2C_NAME_SIZE); + + ret = i2c_attach_client(&state->i2c_client); + if (ret < 0) { + dev_err(dev, "failed to attach client\n"); + kfree(state); + return ret; + } + + dev = &state->i2c_client.dev; + + /* rest of the initialisation goes here. */ + + dev_info(dev, "example client created\n"); + + return 0; +} + +static int __devexit example_detach(struct i2c_client *client) +{ + struct example_state *state = i2c_get_clientdata(client); + + i2c_detach_client(client); + kfree(state); + return 0; +} + +static int example_attach_adapter(struct i2c_adapter *adap) +{ + return i2c_probe(adap, &addr_data, example_attach); +} + +static struct i2c_driver example_driver = { + .driver = { + .owner = THIS_MODULE, + .name = "example", + }, + .attach_adapter = example_attach_adapter, + .detach_client = __devexit_p(example_detach), + .suspend = example_suspend, + .resume = example_resume, +}; + + +Updating the client +------------------- + +The new style binding model will check against a list of supported +devices and their associated address supplied by the code registering +the busses. This means that the driver .attach_adapter and +.detach_adapter methods can be removed, along with the addr_data, +as follows: + +- static struct i2c_driver example_driver; + +- static unsigned short ignore[] = { I2C_CLIENT_END }; +- static unsigned short normal_addr[] = { OUR_ADDR, I2C_CLIENT_END }; + +- I2C_CLIENT_INSMOD; + +- static int example_attach_adapter(struct i2c_adapter *adap) +- { +- return i2c_probe(adap, &addr_data, example_attach); +- } + + static struct i2c_driver example_driver = { +- .attach_adapter = example_attach_adapter, +- .detach_client = __devexit_p(example_detach), + } + +Add the probe and remove methods to the i2c_driver, as so: + + static struct i2c_driver example_driver = { ++ .probe = example_probe, ++ .remove = __devexit_p(example_remove), + } + +Change the example_attach method to accept the new parameters +which include the i2c_client that it will be working with: + +- static int example_attach(struct i2c_adapter *adap, int addr, int kind) ++ static int example_probe(struct i2c_client *client, ++ const struct i2c_device_id *id) + +Change the name of example_attach to example_probe to align it with the +i2c_driver entry names. The rest of the probe routine will now need to be +changed as the i2c_client has already been setup for use. + +The necessary client fields have already been setup before +the probe function is called, so the following client setup +can be removed: + +- example->client.addr = addr; +- example->client.flags = 0; +- example->client.adapter = adap; +- +- strlcpy(client->i2c_client.name, "example", I2C_NAME_SIZE); + +The i2c_set_clientdata is now: + +- i2c_set_clientdata(&state->client, state); ++ i2c_set_clientdata(client, state); + +The call to i2c_attach_client is no longer needed, if the probe +routine exits successfully, then the driver will be automatically +attached by the core. Change the probe routine as so: + +- ret = i2c_attach_client(&state->i2c_client); +- if (ret < 0) { +- dev_err(dev, "failed to attach client\n"); +- kfree(state); +- return ret; +- } + + +Remove the storage of 'struct i2c_client' from the 'struct example_state' +as we are provided with the i2c_client in our example_probe. Instead we +store a pointer to it for when it is needed. + +struct example_state { +- struct i2c_client client; ++ struct i2c_client *client; + +the new i2c client as so: + +- struct device *dev = &adap->dev; /* to use for dev_ reports */ ++ struct device *dev = &i2c_client->dev; /* to use for dev_ reports */ + +And remove the change after our client is attached, as the driver no +longer needs to register a new client structure with the core: + +- dev = &state->i2c_client.dev; + +In the probe routine, ensure that the new state has the client stored +in it: + +static int example_probe(struct i2c_client *i2c_client, + const struct i2c_device_id *id) +{ + struct example_state *state; + struct device *dev = &i2c_client->dev; + int ret; + + state = kzalloc(sizeof(struct example_state), GFP_KERNEL); + if (state == NULL) { + dev_err(dev, "failed to create our state\n"); + return -ENOMEM; + } + ++ state->client = i2c_client; + +Update the detach method, by changing the name to _remove and +to delete the i2c_detach_client call. It is possible that you +can also remove the ret variable as it is not not needed for +any of the core functions. + +- static int __devexit example_detach(struct i2c_client *client) ++ static int __devexit example_remove(struct i2c_client *client) +{ + struct example_state *state = i2c_get_clientdata(client); + +- i2c_detach_client(client); + +And finally ensure that we have the correct ID table for the i2c-core +and other utilities: + ++ struct i2c_device_id example_idtable[] = { ++ { "example", 0 }, ++ { } ++}; ++ ++MODULE_DEVICE_TABLE(i2c, example_idtable); + +static struct i2c_driver example_driver = { + .driver = { + .owner = THIS_MODULE, + .name = "example", + }, ++ .id_table = example_ids, + + +Our driver should now look like this: + +struct example_state { + struct i2c_client *client; + .... +}; + +static int example_probe(struct i2c_client *client, + const struct i2c_device_id *id) +{ + struct example_state *state; + struct device *dev = &client->dev; + + state = kzalloc(sizeof(struct example_state), GFP_KERNEL); + if (state == NULL) { + dev_err(dev, "failed to create our state\n"); + return -ENOMEM; + } + + state->client = client; + i2c_set_clientdata(client, state); + + /* rest of the initialisation goes here. */ + + dev_info(dev, "example client created\n"); + + return 0; +} + +static int __devexit example_remove(struct i2c_client *client) +{ + struct example_state *state = i2c_get_clientdata(client); + + kfree(state); + return 0; +} + +static struct i2c_device_id example_idtable[] = { + { "example", 0 }, + { } +}; + +MODULE_DEVICE_TABLE(i2c, example_idtable); + +static struct i2c_driver example_driver = { + .driver = { + .owner = THIS_MODULE, + .name = "example", + }, + .id_table = example_idtable, + .probe = example_probe, + .remove = __devexit_p(example_remove), + .suspend = example_suspend, + .resume = example_resume, +}; diff --git a/Documentation/i2c/writing-clients b/Documentation/i2c/writing-clients index ee75cbace28d..6b61b3a2e90b 100644 --- a/Documentation/i2c/writing-clients +++ b/Documentation/i2c/writing-clients @@ -25,14 +25,29 @@ routines, and should be zero-initialized except for fields with data you provide. A client structure holds device-specific information like the driver model device node, and its I2C address. +/* iff driver uses driver model ("new style") binding model: */ + +static struct i2c_device_id foo_idtable[] = { + { "foo", my_id_for_foo }, + { "bar", my_id_for_bar }, + { } +}; + +MODULE_DEVICE_TABLE(i2c, foo_idtable); + static struct i2c_driver foo_driver = { .driver = { .name = "foo", }, /* iff driver uses driver model ("new style") binding model: */ + .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, @@ -173,10 +188,9 @@ handle may be used during foo_probe(). If foo_probe() reports success (zero not a negative status code) it may save the handle and use it until foo_remove() returns. That binding model is used by most Linux drivers. -Drivers match devices when i2c_client.driver_name and the driver name are -the same; this approach is used in several other busses that don't have -device typing support in the hardware. The driver and module name should -match, so hotplug/coldplug mechanisms will modprobe the driver. +The probe function is called when an entry in the id_table name field +matches the device's name. It is passed the entry that was matched so +the driver knows which one in the table matched. Device Creation (Standard driver model) @@ -207,6 +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) --------------------------------------- @@ -559,7 +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); @@ -568,30 +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. |
