ACPISMBUS(4)

NAME
acpismbus - ACPI SMBus Control Method Interface

SYNOPSIS
acpismbus* at acpi?
iic* at acpismbus?

DESCRIPTION
The acpismbus driver supports instances of the ACPI SMBus Control Method Interface. This enables i2c access to bus segments which might not otherwise be accessible due to missing "native" driver support. The SMBus Process Call protocol is not supported. All other SMBus protocols are supported to the extent that the underlying controller supports them.

SEE ALSO
acpi(4), iic(4)

HISTORY
The acpismbus driver appeared in NetBSD 6.0.

BUGS
Although acpismbus SMBus Alerts can be associated with individual devices, this capability is ignored. When an acpismbus SMBus Alert is generated, all devices on the i2c bus segment which have registered an interrupt routine are notified.

The SMBus CMI protocol defines a method to provide a list of devices on an i2c bus segment and their addresses. The acpismbus driver makes no attempt to retrieve or process this device list.

There is currently no way to determine if the i2c controller managed by an instance of the ACPI SMBus CMI can also be accessed using a native device driver. Therefore, the acpismbus driver should not be enabled by default. If both a native driver and the acpismbus driver attempt to access the same i2c bus segment, the results are undefined.