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Diffstat (limited to 'cpukit/libi2c/libi2c.h')
| -rw-r--r-- | cpukit/libi2c/libi2c.h | 234 |
1 files changed, 234 insertions, 0 deletions
diff --git a/cpukit/libi2c/libi2c.h b/cpukit/libi2c/libi2c.h new file mode 100644 index 0000000000..761e44a9d2 --- /dev/null +++ b/cpukit/libi2c/libi2c.h @@ -0,0 +1,234 @@ +#ifndef RTEMS_LIBI2C_H +#define RTEMS_LIBI2C_H +/*$Id$*/ +#include <rtems.h> + +#include <rtems/io.h> + +#ifdef __cplusplus +extern "C" { +#endif + +/* Simple I2C driver API */ + +/* Initialize the libary - may fail if no semaphore or no driver slot is available */ +int rtems_libi2c_initialize (); + +/* Bus Driver API + * + * Bus drivers provide access to low-level i2c functions + * such as 'send start', 'send address', 'get bytes' etc. + */ + +/* first field must be a pointer to ops; driver + * may add its own fields after this. + * the struct that is registered with the library + * is not copied; a pointer will we passed + * to the callback functions (ops). + */ +typedef struct rtems_libi2c_bus_t_ +{ + struct rtems_libi2c_bus_ops_ *ops; + int size; /* size of whole structure */ +} rtems_libi2c_bus_t; + +/* Access functions a low level driver must provide; + * + * All of these, except read_bytes and write_bytes + * return RTEMS_SUCCESSFUL on success and an error status + * otherwise. The read and write ops return the number + * of chars read/written or -(status code) on error. + */ +typedef struct rtems_libi2c_bus_ops_ +{ + /* Initialize the bus; might be called again to reset the bus driver */ + rtems_status_code (*init) (rtems_libi2c_bus_t * bushdl); + /* Send start condition */ + rtems_status_code (*send_start) (rtems_libi2c_bus_t * bushdl); + /* Send stop condition */ + rtems_status_code (*send_stop) (rtems_libi2c_bus_t * bushdl); + /* initiate transfer from (rw!=0) or to a device */ + rtems_status_code (*send_addr) (rtems_libi2c_bus_t * bushdl, + unsigned32 addr, int rw); + /* read a number of bytes */ + int (*read_bytes) (rtems_libi2c_bus_t * bushdl, unsigned char *bytes, + int nbytes); + /* write a number of bytes */ + int (*write_bytes) (rtems_libi2c_bus_t * bushdl, unsigned char *bytes, + int nbytes); +} rtems_libi2c_bus_ops_t; + + +/* + * Register a lowlevel driver + * + * TODO: better description + * + * This allocates a major number identifying *this* driver + * (i.e., libi2c) and the minor number encodes a bus# and a i2c address. + * + * The name will be registered in the filesystem (parent + * directories must exist). It may be NULL in which case + * the library will pick a default. + * + * RETURNS: bus # (>=0) or -1 on error (errno set). + */ + +int rtems_libi2c_register_bus (char *name, rtems_libi2c_bus_t * bus); + +extern rtems_device_major_number rtems_libi2c_major; + +#define RTEMS_LIBI2C_MAKE_MINOR(busno, i2caddr) \ + ((((busno)&((1<<3)-1))<<10) | ((i2caddr)&((1<<10)-1))) + +/* After the library is initialized, a major number is available. + * As soon as a low-level bus driver is registered (above routine + * returns a 'busno'), a device node can be created in the filesystem + * with a major/minor number pair of + * + * rtems_libi2c_major / RTEMS_LIBI2C_MAKE_MINOR(busno, i2caddr) + * + * and a 'raw' hi-level driver is then attached to this device + * node. + * This 'raw' driver has very simple semantics: + * + * 'open' sends a start condition + * 'read'/'write' address the device identified by the i2c bus# and address + * encoded in the minor number and read or write, respectively + * a stream of bytes from or to the device. Every time the + * direction is changed, a 're-start' condition followed by + * an 'address' cycle is generated on the i2c bus. + * 'close' sends a stop condition. + * + * Hence, using the 'raw' driver, e.g., 100 bytes at offset 0x200 can be + * read from an EEPROM by the following pseudo-code: + * + * mknod("/dev/i2c-54", mode, MKDEV(rtems_libi2c_major, RTEMS_LIBI2C_MAKE_MINOR(0,0x54))) + * + * int fd; + * char off[2]={0x02,0x00}; + * + * fd = open("/dev/i2c-54",O_RDWR); + * write(fd,off,2); + * read(fd,buf,100); + * close(fd); + * + */ + +/* Higher Level Driver API + * + * Higher level drivers know how to deal with specific i2c + * devices (independent of the bus interface chip) and provide + * an abstraction, i.e., the usual read/write/ioctl access. + * + * Using the above example, such a high level driver could + * prevent the user from issuing potentially destructive write + * operations (the aforementioned EEPROM interprets any 3rd + * and following byte written to the device as data, i.e., the + * contents could easily be changed!). + * The correct 'read-pointer offset' programming could be + * implemented in 'open' and 'ioctl' of a high-level driver and + * the user would then only have to perform harmless read + * operations, e.g., + * + * fd = open("/dev/i2c.eeprom",O_RDONLY) / * opens and sets EEPROM read pointer * / + * ioctl(fd, IOCTL_SEEK, 0x200) / * repositions the read pointer * / + * read(fd, buf, 100) + * close(fd) + * + */ + +/* struct provided at driver registration. The driver may store + * private data behind the mandatory first fields but the size + * must be set to the size of the entire struct, e.g., + * + * struct driver_pvt { + * rtems_libi2c_drv_t pub; + * struct { ... } pvt; + * } my_driver = { + * { ops: my_ops, + * size: sizeof(my_driver) + * }, + * { ...}; + * }; + * + * A pointer to this struct is passed to the callback ops. + */ + +typedef struct rtems_libi2c_drv_t_ +{ + rtems_driver_address_table *ops; /* the driver ops */ + int size; /* size of whole structure (including appended private data) */ +} rtems_libi2c_drv_t; + +/* + * The high level driver must be registered with a particular + * bus number and i2c address. + * + * The registration procedure also creates a filesystem node, + * i.e., the returned minor number is not really needed. + * + * If the 'name' argument is NULL, no filesystem node is + * created (but this can be done 'manually' using rtems_libi2c_major + * and the return value of this routine). + * + * RETURNS minor number (FYI) or -1 on failure + */ +int +rtems_libi2c_register_drv (char *name, rtems_libi2c_drv_t * drvtbl, + unsigned bus, unsigned i2caddr); + +/* Operations available to high level drivers */ + +/* NOTES: The bus a device is attached to is LOCKED from the first send_start + * until send_stop is executed! + * + * Bus tenure MUST NOT span multiple system calls - otherwise, a single + * thread could get into the protected sections (or would deadlock if the + * mutex was not nestable). + * E.g., consider what happens if 'open' sends a 'start' and 'close' + * sends a 'stop' (i.e., the bus mutex would be locked in 'open' and + * released in 'close'. A single thread could try to open two devices + * on the same bus and would either deadlock or nest into the bus mutex + * and potentially mess up the i2c messages. + * + * The correct way is to *always* relinquish the i2c bus (i.e., send 'stop' + * from any driver routine prior to returning control to the caller. + * Consult the implementation of the generic driver routines (open, close, ...) + * below or the examples in i2c-2b-eeprom.c and i2c-2b-ds1621.c + * + * Drivers just pass the minor number on to these routines... + */ +rtems_status_code rtems_libi2c_send_start (rtems_device_minor_number minor); + +rtems_status_code rtems_libi2c_send_stop (rtems_device_minor_number minor); + +rtems_status_code +rtems_libi2c_send_addr (rtems_device_minor_number minor, int rw); + +/* the read/write routines return the number of bytes transferred + * or -(status_code) on error. + */ +int +rtems_libi2c_read_bytes (rtems_device_minor_number minor, + unsigned char *bytes, int nbytes); + +int +rtems_libi2c_write_bytes (rtems_device_minor_number minor, + unsigned char *bytes, int nbytes); + +/* Send start, send address and read bytes */ +int +rtems_libi2c_start_read_bytes (unsigned32 minor, unsigned char *bytes, + int nbytes); + +/* Send start, send address and write bytes */ +int +rtems_libi2c_start_write_bytes (unsigned32 minor, unsigned char *bytes, + int nbytes); + +#ifdef __cplusplus +} +#endif + +#endif |