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Use a single write of 3 bytes instead of iicdev_writeto() in ads111x.

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The iicdev_writeto() function basically does scatter-gather IO by filling
in a pair of iic_msg structs to write the register address then the data
from different locations but with a single bus START/xfer/STOP sequence.
It turns out several low-level i2c controller drivers do not honor the
IIC_NOSTART flag, so the second piece of the write gets a new START on
the bus, and that confuses the ads111x chips which expect a continuous
write of 3 bytes to set a register.

A proper fix for this is to track down all the misbehaving controllers
drivers and fix them.  For now this change makes this driver work again.
This commit is contained in:
Ian Lepore 2019-09-05 19:17:53 +00:00
parent f6a3b357e9
commit acce2d7606
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=351887
1 changed files with 13 additions and 3 deletions
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16
sys/dev/iicbus/ads111x.c
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@ -167,11 +167,21 @@ struct ads111x_softc {
static int
ads111x_write_2(struct ads111x_softc *sc, int reg, int val)
{
uint8_t data[2];
uint8_t data[3];
struct iic_msg msgs[1];
uint8_t slaveaddr;
be16enc(data, val);
slaveaddr = iicbus_get_addr(sc->dev);
return (iic2errno(iicdev_writeto(sc->dev, reg, data, 2, IIC_WAIT)));
data[0] = reg;
be16enc(&data[1], val);
msgs[0].slave = slaveaddr;
msgs[0].flags = IIC_M_WR;
msgs[0].len = sizeof(data);
msgs[0].buf = data;
return (iicbus_transfer_excl(sc->dev, msgs, nitems(msgs), IIC_WAIT));
}
static int