Subject: Re: MI I^2C drivers
To: Castor Fu <>
From: Jason R Thorpe <>
List: tech-kern
Date: 07/26/2000 10:47:26
On Wed, Jul 26, 2000 at 10:30:12AM -0700, Castor Fu wrote:

 > But the stuff in sys/dev/i2c is just not that useful.  We wanted a more
 > general framework.  On our system we have something like the following:
 > 	cai2c0  at chipa?
 > 	iicbus* at cai2c?
 > 	zot0 at iicbus? slaveaddr 0x34          # normalized slave address 
 > 	bar0 at iicbus? slaveaddr 0x46          # normalized slave address
 > The iicbus device has an ioctl for servicing raw io requests through
 > the interface which is also used by child devices.  
 > The io requests at the read/write multiple bytes to support devices
 > like ours where the I2C interface can spit out multiple bytes at a time. 
 > Things get even more complicated if you want to support multiple
 > masters, but I don't know of any systems which take advantage of
 > that part of I2C.
 > I've heard rumors that cgd has similar requirements to ours. . . 
 > If people think this is of general interest we can start iterating on
 > a common framework.

Also take into consideration SMBus, please, and the fact that not all
host controllers are bit-bangers.

        -- Jason R. Thorpe <>