Adding V4L folks to Cc for more input.
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.
- 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.
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.
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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