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author | Mauro Carvalho Chehab <mchehab+huawei@kernel.org> | 2020-03-04 10:21:39 +0100 |
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committer | Mauro Carvalho Chehab <mchehab+huawei@kernel.org> | 2020-04-14 10:31:49 +0200 |
commit | 54f38fcae536ea202ce7d6a359521492fba30c1f (patch) | |
tree | dd1a2b36d8de0b13702f2716526ad3b91650e090 /Documentation/media/uapi/v4l/dev-touch.rst | |
parent | 5dfb8db56b273740a76e8687ee7efb4b2c0ec83b (diff) |
media: docs: move uAPI book to userspace-api/media
Since 2017, there is an space reserved for userspace API,
created by changeset 1d596dee3862 ("docs: Create a user-space API guide").
As the media subsystem was one of the first subsystems to use
Sphinx, until this patch, we were keeping things on a separate
place.
Let's just use the new location, as having all uAPI altogether
will likely make things easier for developers.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Diffstat (limited to 'Documentation/media/uapi/v4l/dev-touch.rst')
-rw-r--r-- | Documentation/media/uapi/v4l/dev-touch.rst | 63 |
1 files changed, 0 insertions, 63 deletions
diff --git a/Documentation/media/uapi/v4l/dev-touch.rst b/Documentation/media/uapi/v4l/dev-touch.rst deleted file mode 100644 index 356f01385221..000000000000 --- a/Documentation/media/uapi/v4l/dev-touch.rst +++ /dev/null @@ -1,63 +0,0 @@ -.. Permission is granted to copy, distribute and/or modify this -.. document under the terms of the GNU Free Documentation License, -.. Version 1.1 or any later version published by the Free Software -.. Foundation, with no Invariant Sections, no Front-Cover Texts -.. and no Back-Cover Texts. A copy of the license is included at -.. Documentation/media/uapi/fdl-appendix.rst. -.. -.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections - -.. _touch: - -************* -Touch Devices -************* - -Touch devices are accessed through character device special files named -``/dev/v4l-touch0`` to ``/dev/v4l-touch255`` with major number 81 and -dynamically allocated minor numbers 0 to 255. - -Overview -======== - -Sensors may be Optical, or Projected Capacitive touch (PCT). - -Processing is required to analyse the raw data and produce input events. In -some systems, this may be performed on the ASIC and the raw data is purely a -side-channel for diagnostics or tuning. In other systems, the ASIC is a simple -analogue front end device which delivers touch data at high rate, and any touch -processing must be done on the host. - -For capacitive touch sensing, the touchscreen is composed of an array of -horizontal and vertical conductors (alternatively called rows/columns, X/Y -lines, or tx/rx). Mutual Capacitance measured is at the nodes where the -conductors cross. Alternatively, Self Capacitance measures the signal from each -column and row independently. - -A touch input may be determined by comparing the raw capacitance measurement to -a no-touch reference (or "baseline") measurement: - -Delta = Raw - Reference - -The reference measurement takes account of variations in the capacitance across -the touch sensor matrix, for example manufacturing irregularities, -environmental or edge effects. - -Querying Capabilities -===================== - -Devices supporting the touch interface set the ``V4L2_CAP_VIDEO_CAPTURE`` flag -and the ``V4L2_CAP_TOUCH`` flag in the ``capabilities`` field of -:c:type:`v4l2_capability` returned by the -:ref:`VIDIOC_QUERYCAP` ioctl. - -At least one of the read/write or streaming I/O methods must be -supported. - -The formats supported by touch devices are documented in -:ref:`Touch Formats <tch-formats>`. - -Data Format Negotiation -======================= - -A touch device may support any I/O method. |