From: Chris Wolfe <cwolfe@chromium.org>
To: Alan Cox <alan@linux.intel.com>
Cc: Nathan Royer <nroyer@invensense.com>,
Andrew Morton <akpm@linux-foundation.org>,
Greg Kroah-Hartman <gregkh@suse.de>,
Jonathan Cameron <jic23@cam.ac.uk>, Jiri Kosina <jkosina@suse.cz>,
Jean Delvare <khali@linux-fr.org>,
linux-kernel@vger.kernel.org, linux-input@vger.kernel.org
Subject: Re: [PATCH 11/11] misc: Add slave driver for bma085 pressure sensor
Date: Fri, 1 Jul 2011 07:28:53 -0700 [thread overview]
Message-ID: <CAN_12A8Za7r92=r3JHx3R=AwAA7xk6=NVVMiSp68HPatb1G3hg@mail.gmail.com> (raw)
In-Reply-To: <20110701085604.0aabd6f1@bob.linux.org.uk>
On Fri, Jul 1, 2011 at 12:56 AM, Alan Cox <alan@linux.intel.com> wrote:
> The slave devices all appear to be generic i2c interface hardware. I
> don't see why they are separate special slave devices to your driver,
> they should simply be i²c drivers so they can be used when those
> devices are found without the mpu3050.
Just to field this quickly, since I've been playing with the hardware
involved. There are actually two different things handled by the
"slave devices".
The MPU-3050 (and some similar InvenSense parts) provide a secondary
I2C bus. By default this is passed through to the I2C bus on which the
3050 is installed, but the MPU can also detach the extra bus and act
as an I2C master on it. A slave device is connected on this extra bus,
configured normally by the kernel, and then taken over by the MPU
(which will periodically do a block read of a configured address).
The second case of a slave device is simply some other device that the
driver reads from, and passes the data to the MPU for processing.
Part of the reason I got started on the KXTF9 driver was to try and
understand how a normal kernel driver could cope with the "here and
gone again" behavior of being on the MPU's secondary bus.
The other note that may not have been made explicit yet is that the
3050 will happily provide unprocessed gyro and slave data without
firmware loaded. The firmware sets up some additional processing
capabilities of the chip, which are used by InvenSense's user-space
products.
Chris
[Sorry about gmail. I'm on the road and hope it doesn't mangle things
too badly.]
next prev parent reply other threads:[~2011-07-01 14:29 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-01 2:18 [PATCH 01/11] misc: inv_mpu primary header file and README file Nathan Royer
2011-07-01 2:18 ` [PATCH 02/11] misc: mpu3050 Register definition and Private data Nathan Royer
2011-07-01 2:18 ` [PATCH 03/11] misc: mpu3050 /dev/mpu implementation Nathan Royer
2011-07-01 2:18 ` [PATCH 04/11] misc: IRQ handling for MPU3050 and slave devices Nathan Royer
2011-07-01 2:18 ` [PATCH 05/11] misc: MPU3050 and slave device configuration Nathan Royer
2011-07-01 17:55 ` Nathan Royer
2011-07-01 2:18 ` [PATCH 06/11] misc: inv_mpu logging and debugging support Nathan Royer
2011-07-01 2:18 ` [PATCH 07/11] misc: I2C communication with the MPU3050 and slave devices Nathan Royer
2011-07-01 2:18 ` [PATCH 08/11] misc: Kconfig and Makefile changes for inv_mpu driver Nathan Royer
2011-07-01 17:10 ` Randy Dunlap
2011-07-01 2:18 ` [PATCH 09/11] misc: Add slave driver for kxtf9 accelerometer Nathan Royer
2011-07-01 2:18 ` [PATCH 10/11] misc: Add slave driver for ak8975 compass driver Nathan Royer
2011-07-01 2:18 ` [PATCH 11/11] misc: Add slave driver for bma085 pressure sensor Nathan Royer
2011-07-01 7:56 ` Alan Cox
2011-07-01 8:47 ` Jean Delvare
2011-07-01 14:28 ` Chris Wolfe [this message]
2011-07-01 14:41 ` Alan Cox
2011-07-01 15:52 ` Chris Wolfe
2011-07-01 17:00 ` Alan Cox
2011-07-01 17:56 ` Nathan Royer
2011-07-01 16:09 ` Jean Delvare
2011-07-01 9:05 ` Jonathan Cameron
2011-07-01 10:35 ` Manuel Stahl
2011-07-01 3:09 ` [PATCH 01/11] misc: inv_mpu primary header file and README file Greg KH
2011-07-01 7:29 ` Alan Cox
2011-07-01 9:00 ` Jonathan Cameron
2011-07-01 3:59 ` Chris Wolfe
2011-07-05 18:08 ` Nathan Royer
2011-07-01 7:53 ` Alan Cox
2011-07-01 9:08 ` Jonathan Cameron
2011-07-01 16:39 ` Nathan Royer
2011-07-03 11:29 ` Jonathan Cameron
2011-07-04 8:16 ` Alan Cox
2011-07-06 1:49 ` Nathan Royer
2011-07-06 9:07 ` Jonathan Cameron
2011-07-06 20:25 ` Nathan Royer
2011-07-06 10:54 ` Alan Cox
2011-07-06 21:27 ` Nathan Royer
2011-07-07 7:40 ` Alan Cox
2011-07-08 1:25 ` Nathan Royer
2011-07-08 11:21 ` Jonathan Cameron
2011-07-08 16:24 ` Nathan Royer
2011-07-04 20:06 ` Eric Andersson
2011-07-01 21:04 ` Arnd Bergmann
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