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author | Linus Torvalds <torvalds@linux-foundation.org> | 2016-10-11 13:22:22 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-10-11 13:22:22 -0700 |
commit | de34f4da7f62ff59ac6e1ef320b0fcfa3296fce3 (patch) | |
tree | 88b5db2fc7fbbb0353edd8447a832a5225a49d01 /Documentation/media/uapi/v4l/dev-touch.rst | |
parent | 56e520c7a0a490b63b042b047ec9659fc08762a4 (diff) | |
parent | 9fce0c226536fc36c7fb0a80000ca38a995be43e (diff) |
Merge tag 'media/v4.9-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media
Pull media updates from Mauro Carvalho Chehab:
- Documentation improvements: conversion of all non-DocBook documents
to Sphinx and lots of fixes to the uAPI media book
- New PCI driver for Techwell TW5864 media grabber boards
- New SoC driver for ATMEL Image Sensor Controller
- Removal of some obsolete SoC drivers (s5p-tv driver and soc_camera
drivers)
- Addition of ST CEC driver
- Lots of drivers fixes, improvements and additions
* tag 'media/v4.9-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media: (464 commits)
[media] ttusb_dec: avoid the risk of go past buffer
[media] cx23885: Fix some smatch warnings
[media] si2165: switch to regmap
[media] si2165: use i2c_client->dev instead of i2c_adapter->dev for logging
[media] si2165: Remove legacy attach
[media] cx231xx: attach si2165 driver via i2c_client
[media] cx231xx: Prepare for attaching new style i2c_client DVB demod drivers
[media] cx23885: attach si2165 driver via i2c_client
[media] si2165: support i2c_client attach
[media] si2165: avoid division by zero
[media] rcar-vin: add R-Car gen2 fallback compatibility string
[media] lgdt3306a: remove 20*50 msec unnecessary timeout
[media] cx25821: Remove deprecated create_singlethread_workqueue
[media] cx25821: Drop Freeing of Workqueue
[media] cxd2841er: force 8MHz bandwidth for DVB-C if specified bw not supported
[media] redrat3: hardware-specific parameters
[media] redrat3: remove hw_timeout member
[media] cxd2841er: BER and SNR reading for ISDB-T
[media] dvb-usb: avoid link error with dib3000m{b,c|
[media] dvb-usb: split out common parts of dibusb
...
Diffstat (limited to 'Documentation/media/uapi/v4l/dev-touch.rst')
-rw-r--r-- | Documentation/media/uapi/v4l/dev-touch.rst | 56 |
1 files changed, 56 insertions, 0 deletions
diff --git a/Documentation/media/uapi/v4l/dev-touch.rst b/Documentation/media/uapi/v4l/dev-touch.rst new file mode 100644 index 000000000000..98797f255ce0 --- /dev/null +++ b/Documentation/media/uapi/v4l/dev-touch.rst @@ -0,0 +1,56 @@ +.. -*- coding: utf-8; mode: rst -*- + +.. _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. |