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

[Jonathan Cameron <jic23@kernel.org>]

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.. 
> 
> 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
>