Re: [RFC PATCH 0/3] Introduce IIO interface for fingerprint sensors

["Baluta, Teodora" <teodora.baluta@intel.com>]

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On Vi, 2014-12-26 at 11:13 +0000, Jonathan Cameron wrote:
> On 18/12/14 16:51, Lars-Peter Clausen wrote:
> > Adding V4L folks to Cc for more input.
> Thanks Lars - we definitely would need the v4l guys to agree to a driver like
> this going in IIO. (not that I'm convinced it should!)
> > 
> > On 12/08/2014 03:10 PM, Baluta, Teodora wrote:
> >> Hello,
> >>
> >> On Vi, 2014-12-05 at 02:15 +0000, Jonathan Cameron wrote:
> >>> On 04/12/14 13:00, Teodora Baluta wrote:
> >>>> This patchset adds support for fingerprint sensors through the IIO interface.
> >>>> This way userspace applications collect information in a uniform way. All
> >>>> processing would be done in the upper layers as suggested in [0].
> >>>>
> >>>> In order to test out this proposal, a minimal implementation for UPEK's
> >>>> TouchChip Fingerprint Sensor via USB is also available. Although there is an
> >>>> existing implementation in userspace for USB fingerprint devices, including this
> >>>> particular device, the driver represents a proof of concept of how fingerprint
> >>>> sensors could be integrated in the IIO framework regardless of the used bus. For
> >>>> lower power requirements, the SPI bus is preferred and a kernel driver
> >>>> implementation makes more sense.
> >>>
> >>> So why not v4l?  These are effectively image sensors..
> >>
> >> Well, here's why I don't think v4l would be the best option:
> >>
> >> - an image scanner could be implemented in the v4l subsystem, but it
> >> seems far more complicated for a simple fingerprint scanner - it usually
> >> has drivers for webcams, TVs or video streaming devices. The v4l
> >> subsystem (with all its support for colorspace, decoders, image
> >> compression, frame control) seems a bit of an overkill for a very
> >> straightforward fingerprint imaging sensor.
> Whilst those are there, I would doubt the irrelevant bits would put much
> burden on a fingerprint scanning driver.  Been a while since I did
> anything in that area though so I could be wrong!
> >>
> >> - a fingerprint device could also send out a processed information, not
> >> just the image of a fingerprint. This means that the processing is done
> >> in hardware - the UPEK TouchStrip chipset in libfprint has this behavior
> >> (see [0]). So, the IIO framework would support a uniform way of handling
> >> fingerprint devices that either do processing in software or in
> >> hardware.
> This is more interesting, but does that map well to IIO style
> channels anyway?  If not we are going to end up with a whole new
> interface which ever subsystem is used for the image side of things.
> >>
> >> The way I see it now, for processed fingerprint information, an IIO
> >> device could have an IIO_FINGERPRINT channel with a modifier and only
> >> the sensitivity threshold attribute set. We would also need two
> >> triggers: one for enrollment and one for the verification mode to
> >> control the device from a userspace application.
> Sure - what you proposed would work.  The question is whether it is
> the best way to do it.

Any thoughts on this from the v4l community?

Thanks,
Teodora

> 
> 
> >>
> >> Thanks,
> >> Teodora
> >>
> >> [0] http://www.freedesktop.org/wiki/Software/fprint/libfprint/upekts/
> >>
> >>
> >>>>
> >>>> A sysfs trigger is enabled and the device starts scanning. As soon as an image
> >>>> is available it is written in the character device /dev/iio:deviceX.
> >>>>
> >>>> Userspace applications will be able to calculate the expected image size using
> >>>> the fingerprint attributes height, width and bit depth. Other attributes
> >>>> introduced for the fingerprint channel in IIO represent information that aids in
> >>>> the fingerprint image processing. Besides these, the proposed interface offers
> >>>> userspace a way to read a feedback after a scan (like the swipe was too slow or
> >>>> too fast) through a modified fingerprint_status channel.
> >>>>
> >>>> [0] http://www.spinics.net/lists/linux-iio/msg11463.html
> >>>>
> >>>> Teodora Baluta (3):
> >>>>    iio: core: add support for fingerprint devices
> >>>>    iio: core: change channel's storagebits/realbits to u32
> >>>>    iio: fingerprint: add fingerprint sensor via USB
> >>>>
> >>>>   Documentation/ABI/testing/sysfs-bus-iio |  51 +++
> >>>>   drivers/iio/Kconfig                     |   1 +
> >>>>   drivers/iio/Makefile                    |   1 +
> >>>>   drivers/iio/fingerprint/Kconfig         |  15 +
> >>>>   drivers/iio/fingerprint/Makefile        |   5 +
> >>>>   drivers/iio/fingerprint/fp_tc.c         | 162 +++++++++
> >>>>   drivers/iio/fingerprint/fp_tc.h         |  22 ++
> >>>>   drivers/iio/fingerprint/fp_tc_usb.c     | 618 ++++++++++++++++++++++++++++++++
> >>>>   drivers/iio/fingerprint/fp_tc_usb.h     | 144 ++++++++
> >>>>   drivers/iio/industrialio-core.c         |   9 +
> >>>>   include/linux/iio/iio.h                 |  11 +-
> >>>>   include/linux/iio/types.h               |  10 +
> >>>>   12 files changed, 1047 insertions(+), 2 deletions(-)
> >>>>   create mode 100644 drivers/iio/fingerprint/Kconfig
> >>>>   create mode 100644 drivers/iio/fingerprint/Makefile
> >>>>   create mode 100644 drivers/iio/fingerprint/fp_tc.c
> >>>>   create mode 100644 drivers/iio/fingerprint/fp_tc.h
> >>>>   create mode 100644 drivers/iio/fingerprint/fp_tc_usb.c
> >>>>   create mode 100644 drivers/iio/fingerprint/fp_tc_usb.h
> >>>>
> >>>
> >>
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> >>
> > 
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