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Add a pair of convenience routines for doing simple "register" read/writes

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on i2c devices, where the "register" can be any length.

Many (perhaps most) common i2c devices are organized as a collection of
(usually 1-byte-wide) registers, and are accessed by first writing a 1-byte
register index/offset number, then by reading or writing the data.
Generally there is an auto-increment feature so the when multiple bytes
are read or written, multiple contiguous registers are accessed.

Most existing slave device drivers allocate an array of iic_msg structures,
fill in all the transfer info, and invoke iicbus_transfer().  These new
functions commonize all that and reduce register access to a simple call
with a few arguments.
This commit is contained in:
Ian Lepore 2017-07-26 20:40:24 +00:00
parent c45b18681f
commit 7ec74c580d
2 changed files with 62 additions and 0 deletions
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52
sys/dev/iicbus/iiconf.c
View File

@ -470,3 +470,55 @@ iicbus_transfer_gen(device_t dev, struct iic_msg *msgs, uint32_t nmsgs)
iicbus_stop(bus);
return (error);
}
int
iicdev_readfrom(device_t slavedev, uint8_t regaddr, void *buffer,
uint16_t buflen, int waithow)
{
struct iic_msg msgs[2];
uint8_t slaveaddr;
/*
* Two transfers back to back with a repeat-start between them; first we
* write the address-within-device, then we read from the device.
*/
slaveaddr = iicbus_get_addr(slavedev);
msgs[0].slave = slaveaddr;
msgs[0].flags = IIC_M_WR | IIC_M_NOSTOP;
msgs[0].len = 1;
msgs[0].buf = &regaddr;
msgs[1].slave = slaveaddr;
msgs[1].flags = IIC_M_RD;
msgs[1].len = buflen;
msgs[1].buf = buffer;
return (iicbus_transfer_excl(slavedev, msgs, nitems(msgs), waithow));
}
int iicdev_writeto(device_t slavedev, uint8_t regaddr, void *buffer,
uint16_t buflen, int waithow)
{
struct iic_msg msgs[2];
uint8_t slaveaddr;
/*
* Two transfers back to back with no stop or start between them; first
* we write the address then we write the data to that address, all in a
* single transfer from two scattered buffers.
*/
slaveaddr = iicbus_get_addr(slavedev);
msgs[0].slave = slaveaddr;
msgs[0].flags = IIC_M_WR | IIC_M_NOSTOP;
msgs[0].len = 1;
msgs[0].buf = &regaddr;
msgs[1].slave = slaveaddr;
msgs[1].flags = IIC_M_WR | IIC_M_NOSTART;
msgs[1].len = buflen;
msgs[1].buf = buffer;
return (iicbus_transfer_excl(slavedev, msgs, nitems(msgs), waithow));
}

10
sys/dev/iicbus/iiconf.h
View File

@ -133,6 +133,16 @@ int iicbus_transfer_excl(device_t bus, struct iic_msg *msgs, uint32_t nmsgs,
int how);
int iicbus_transfer_gen(device_t bus, struct iic_msg *msgs, uint32_t nmsgs);
/*
* Simple register read/write routines, but the "register" can be any size.
* The transfers are done with iicbus_transfer_excl(). Reads use a repeat-start
* between sending the address and reading; writes use a single start/stop.
*/
int iicdev_readfrom(device_t _slavedev, uint8_t _regaddr, void *_buffer,
uint16_t _buflen, int _waithow);
int iicdev_writeto(device_t _slavedev, uint8_t _regaddr, void *_buffer,
uint16_t _buflen, int _waithow);
#define IICBUS_MODVER 1
#define IICBUS_MINVER 1
#define IICBUS_MAXVER 1