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    SubjectRe: [PATCH RESEND] HID: New hid-cp2112 driver.
    On 08/28/2013 07:57 AM, Jiri Kosina wrote:
    >
    > [ adding Benjamin to CC ]
    >
    > On Tue, 27 Aug 2013, David Barksdale wrote:
    >
    >> This patch adds support for the Silicon Labs CP2112
    >> "Single-Chip HID USB to SMBus Master Bridge."
    >>
    >> I wrote this to support a USB temperature and humidity
    >> sensor I've been working on. It's been tested by using
    >> SMBus byte-read, byte-data-read/write, and word-data-read
    >> transfer modes to talk to an I2C sensor. The other
    >> transfer modes have not been tested.
    >>
    >> Signed-off-by: David Barksdale <dbarksdale@uplogix.com>
    >>
    >> ---
    >> drivers/hid/Kconfig | 6 +
    >> drivers/hid/Makefile | 1 +
    >> drivers/hid/hid-core.c | 3 +
    >> drivers/hid/hid-cp2112.c | 504 +++++++++++++++++++++++++++++++++++++++++++++++
    >> 4 files changed, 514 insertions(+)
    >>
    >> diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
    >> index 14ef6ab..1833948 100644
    >> --- a/drivers/hid/Kconfig
    >> +++ b/drivers/hid/Kconfig
    >> @@ -175,6 +175,12 @@ config HID_PRODIKEYS
    >> multimedia keyboard, but will lack support for the musical keyboard
    >> and some additional multimedia keys.
    >>
    >> +config HID_CP2112
    >> + tristate "Silicon Labs CP2112 HID USB-to-SMBus Bridge support"
    >> + depends on USB_HID
    >> + ---help---
    >> + Support for Silicon Labs CP2112 HID USB to SMBus Master Bridge.
    >> +
    >
    > Hi David,
    >
    > this is rather difficult to get by quickly looking at the code, so I'd
    > like to have a slightly better overview of what the device really is.
    >
    > Is it talking HID protocol on the SMBus? (if so, there is a hid-i2c
    > transport driver for it already).
    > But I guess this is not really the case, as you seem to be using the USB
    > HID functionality as well.
    >
    > Thanks in advance for some more background.
    >

    The CP2112 is a USB HID device that provides an SMBus controller.
    The datasheet can be found here:
    http://www.silabs.com/Support%20Documents/TechnicalDocs/CP2112.pdf
    The interface specification here:
    http://www.silabs.com/Support%20Documents/TechnicalDocs/AN495.pdf
    The host communicates with the CP2112 via HID reports. Device
    configuration uses feature reports and data transfer uses output and
    event reports.
    I prototyped this in userspace using the /dev/hidraw interface and then
    wrote this driver to provide a real i2c adapter device.


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