add iic interface to ig4 driver, move isl and cyapa to iicbus
Summary:
The hardware does not expose a classic SMBus interface.
Instead it has a lower level interface that can express a far richer
I2C protocol than what smbus offers. However, the interface does not
provide a way to explicitly generate the I2C stop and start conditions.
It's only possible to request that the stop condition is generated
after transferring the next byte in either direction. So, at least
one data byte must always be transferred.
Thus, some I2C sequences are impossible to generate, e.g., an equivalent
of smbus quick command (<start>-<slave addr>-<r/w bit>-<stop>).
At the same time isl(4) and cyapa(4) are moved to iicbus and now they use
iicbus_transfer for communication. Previously they used smbus_trans()
interface that is not defined by the SMBus protocol and was implemented
only by ig4(4). In fact, that interface was impossible to implement
for the typical SMBus controllers like intpm(4) or ichsmb(4) where
a type of the SMBus command must be programmed.
The plan is to remove smbus_trans() and all its uses.
As an aside, the smbus_trans() method deviates from the standard,
but perhaps backwards, FreeBSD convention of using 8-bit slave
addresses (shifted by 1 bit to the left). The method expects
7-bit addresses.
There is a user facing consequence of this change.
A user must now provide device hints for isl and cyapa that specify an iicbus to use
and a slave address on it.
On Chromebook hardware where isl and cyapa devices are commonly found
it is also possible to use a new chromebook_platform(4) driver that
automatically configures isl and cyapa devices. There is no need to
provide the device hints in that case,
Right now smbus(4) driver tries to discover all slaves on the bus.
That is very dangerous. Fortunately, the probing code uses smbus_trans()
to do its job, so it is really enabled for ig4 only.
The plan is to remove that auto-probing code and smbus_trans().
Tested by: grembo, Matthias Apitz <guru@unixarea.de> (w/o
chromebook_platform)
Discussed with: grembo, imp
Reviewed by: wblock (docs)
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D8172
2016-10-30 12:15:33 +00:00
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.\" Copyright (c) 2016 Andriy Gapon <avg@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd October 13, 2016
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.Dt CHROMEBOOK_PLATFORM 4
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.Os
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.Sh NAME
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.Nm chromebook_platform
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.Nd support driver for hardware on various Chromebook models
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.Sh SYNOPSIS
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To compile this driver into the kernel, place the following lines into
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the kernel configuration file:
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.Bd -ragged -offset indent
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.Cd "device chromebook_platform"
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.Ed
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.Pp
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Alternatively, to load the driver as a module at boot time, place the following line in
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.Xr loader.conf 5 :
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.Bd -literal -offset indent
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chromebook_platform_load="YES"
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.Ed
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.Sh DESCRIPTION
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The
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.Nm
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driver provides automatic configuration for devices that cannot be enumerated
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or safely probed.
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In particular, I2C peripherals are different from model to model.
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.Nm
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has a model-specific information about the I2C peripherals, their drivers,
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their bus attachments and slave addresses.
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.Pp
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Note that
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.Nm
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does not load driver modules for the peripherals.
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Those have to be compiled into the kernel or loaded separately.
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.Sh SEE ALSO
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.Xr cyapa 4 ,
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.Xr iicbus 4 ,
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2016-11-23 18:45:15 +00:00
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.Xr isl 4
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add iic interface to ig4 driver, move isl and cyapa to iicbus
Summary:
The hardware does not expose a classic SMBus interface.
Instead it has a lower level interface that can express a far richer
I2C protocol than what smbus offers. However, the interface does not
provide a way to explicitly generate the I2C stop and start conditions.
It's only possible to request that the stop condition is generated
after transferring the next byte in either direction. So, at least
one data byte must always be transferred.
Thus, some I2C sequences are impossible to generate, e.g., an equivalent
of smbus quick command (<start>-<slave addr>-<r/w bit>-<stop>).
At the same time isl(4) and cyapa(4) are moved to iicbus and now they use
iicbus_transfer for communication. Previously they used smbus_trans()
interface that is not defined by the SMBus protocol and was implemented
only by ig4(4). In fact, that interface was impossible to implement
for the typical SMBus controllers like intpm(4) or ichsmb(4) where
a type of the SMBus command must be programmed.
The plan is to remove smbus_trans() and all its uses.
As an aside, the smbus_trans() method deviates from the standard,
but perhaps backwards, FreeBSD convention of using 8-bit slave
addresses (shifted by 1 bit to the left). The method expects
7-bit addresses.
There is a user facing consequence of this change.
A user must now provide device hints for isl and cyapa that specify an iicbus to use
and a slave address on it.
On Chromebook hardware where isl and cyapa devices are commonly found
it is also possible to use a new chromebook_platform(4) driver that
automatically configures isl and cyapa devices. There is no need to
provide the device hints in that case,
Right now smbus(4) driver tries to discover all slaves on the bus.
That is very dangerous. Fortunately, the probing code uses smbus_trans()
to do its job, so it is really enabled for ig4 only.
The plan is to remove that auto-probing code and smbus_trans().
Tested by: grembo, Matthias Apitz <guru@unixarea.de> (w/o
chromebook_platform)
Discussed with: grembo, imp
Reviewed by: wblock (docs)
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D8172
2016-10-30 12:15:33 +00:00
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.Sh AUTHORS
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.An -nosplit
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The
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.Nm
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driver and this manual page were written by
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.An Andriy Gapon Aq Mt avg@FreeBSD.org .
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