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Input: rotary-encoder - convert documentation into to ReST format
This file require minimum adjustments to be a valid ReST file.
Do it, in order to be able to parse it with Sphinx.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
authored by
Mauro Carvalho Chehab
and committed by
Dmitry Torokhov
42f2309b
7b11fdc3
+38
-36
+38
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Documentation/input/rotary-encoder.txt
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Documentation/input/rotary-encoder.txt
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============================================================
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rotary-encoder - a generic driver for GPIO connected devices
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Daniel Mack <daniel@caiaq.de>, Feb 2009
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============================================================
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0. Function
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-----------
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:Author: Daniel Mack <daniel@caiaq.de>, Feb 2009
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Function
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--------
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Rotary encoders are devices which are connected to the CPU or other
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peripherals with two wires. The outputs are phase-shifted by 90 degrees
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a stable state with both outputs high (half-period mode) and some have
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a stable state in all steps (quarter-period mode).
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The phase diagram of these two outputs look like this:
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The phase diagram of these two outputs look like this::
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_____ _____ _____
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| | | | | |
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https://en.wikipedia.org/wiki/Rotary_encoder
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1. Events / state machine
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-------------------------
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Events / state machine
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----------------------
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In half-period mode, state a) and c) above are used to determine the
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rotational direction based on the last stable state. Events are reported in
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should have happened, unless it flipped back on half the way. The
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'armed' state tells us about that.
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2. Platform requirements
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------------------------
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Platform requirements
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---------------------
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As there is no hardware dependent call in this driver, the platform it is
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used with must support gpiolib. Another requirement is that IRQs must be
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able to fire on both edges.
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3. Board integration
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--------------------
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Board integration
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-----------------
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To use this driver in your system, register a platform_device with the
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name 'rotary-encoder' and associate the IRQs and some specific platform
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Because GPIO to IRQ mapping is platform specific, this information must
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be given in separately to the driver. See the example below.
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---------<snip>---------
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::
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/* board support file example */
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/* board support file example */
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#include <linux/input.h>
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#include <linux/rotary_encoder.h>
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#include <linux/input.h>
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#include <linux/rotary_encoder.h>
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#define GPIO_ROTARY_A 1
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#define GPIO_ROTARY_B 2
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#define GPIO_ROTARY_A 1
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#define GPIO_ROTARY_B 2
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static struct rotary_encoder_platform_data my_rotary_encoder_info = {
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.steps = 24,
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.axis = ABS_X,
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.relative_axis = false,
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.rollover = false,
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.gpio_a = GPIO_ROTARY_A,
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.gpio_b = GPIO_ROTARY_B,
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.inverted_a = 0,
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.inverted_b = 0,
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.half_period = false,
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.wakeup_source = false,
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};
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static struct rotary_encoder_platform_data my_rotary_encoder_info = {
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.steps = 24,
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.axis = ABS_X,
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.relative_axis = false,
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.rollover = false,
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.gpio_a = GPIO_ROTARY_A,
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.gpio_b = GPIO_ROTARY_B,
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.inverted_a = 0,
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.inverted_b = 0,
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.half_period = false,
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.wakeup_source = false,
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};
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static struct platform_device rotary_encoder_device = {
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.name = "rotary-encoder",
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.id = 0,
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.dev = {
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.platform_data = &my_rotary_encoder_info,
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}
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};
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static struct platform_device rotary_encoder_device = {
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.name = "rotary-encoder",
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.id = 0,
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.dev = {
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.platform_data = &my_rotary_encoder_info,
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}
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};