[PATCH v5 2/4] button: add a simple Analog to Digital Converter device based button driver
Marek Szyprowski
m.szyprowski at samsung.com
Tue Jan 26 12:25:04 CET 2021
Hi Heinrich,
On 26.01.2021 12:10, Heinrich Schuchardt wrote:
> On 1/26/21 10:50 AM, Marek Szyprowski wrote:
>> Add a simple Analog to Digital Converter device based button driver.
>> This
>> driver binds to the 'adc-keys' device tree node.
>>
>> Signed-off-by: Marek Szyprowski <m.szyprowski at samsung.com>
>> ---
>> drivers/button/Kconfig | 8 ++
>> drivers/button/Makefile | 1 +
>> drivers/button/button-adc.c | 156 ++++++++++++++++++++++++++++++++++++
>> 3 files changed, 165 insertions(+)
>> create mode 100644 drivers/button/button-adc.c
>>
>> diff --git a/drivers/button/Kconfig b/drivers/button/Kconfig
>> index 6b3ec7e55d..6db3c5e93a 100644
>> --- a/drivers/button/Kconfig
>> +++ b/drivers/button/Kconfig
>> @@ -9,6 +9,14 @@ config BUTTON
>> can provide access to board-specific buttons. Use of the
>> device tree
>> for configuration is encouraged.
>>
>> +config BUTTON_ADC
>> + bool "Button adc"
>> + depends on BUTTON
>> + help
>> + Enable support for buttons which are connected to Analog to
>> Digital
>> + Converter device. The ADC driver must use driver model.
>> Buttons are
>> + configured using the device tree.
>> +
>> config BUTTON_GPIO
>> bool "Button gpio"
>> depends on BUTTON
>> diff --git a/drivers/button/Makefile b/drivers/button/Makefile
>> index fcc10ebe8d..bbd18af149 100644
>> --- a/drivers/button/Makefile
>> +++ b/drivers/button/Makefile
>> @@ -3,4 +3,5 @@
>> # Copyright (C) 2020 Philippe Reynes <philippe.reynes at softathome.com>
>>
>> obj-$(CONFIG_BUTTON) += button-uclass.o
>> +obj-$(CONFIG_BUTTON_ADC) += button-adc.o
>> obj-$(CONFIG_BUTTON_GPIO) += button-gpio.o
>> diff --git a/drivers/button/button-adc.c b/drivers/button/button-adc.c
>> new file mode 100644
>> index 0000000000..1901d59a0e
>> --- /dev/null
>> +++ b/drivers/button/button-adc.c
>> @@ -0,0 +1,156 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright (C) 2021 Samsung Electronics Co., Ltd.
>> + * http://www.samsung.com
>> + * Author: Marek Szyprowski <m.szyprowski at samsung.com>
>> + */
>> +
>> +#include <common.h>
>> +#include <adc.h>
>> +#include <button.h>
>> +#include <log.h>
>> +#include <dm.h>
>> +#include <dm/lists.h>
>> +#include <dm/of_access.h>
>> +#include <dm/uclass-internal.h>
>> +
>> +/**
>> + * struct button_adc_priv - private data for button-adc driver.
>> + *
>> + * @adc: Analog to Digital Converter device to which button is
>> connected.
>> + * @channel: channel of the ADC device to probe the button state.
>> + * @min: minimal raw ADC sample value to consider button as pressed.
>> + * @max: maximal raw ADC sample value to consider button as pressed.
>> + */
>> +struct button_adc_priv {
>> + struct udevice *adc;
>> + int channel;
>> + int min;
>> + int max;
>> +};
>> +
>> +static enum button_state_t button_adc_get_state(struct udevice *dev)
>> +{
>> + struct button_adc_priv *priv = dev_get_priv(dev);
>> + unsigned int val;
>> + int ret;
>> +
>> + ret = adc_start_channel(priv->adc, priv->channel);
>> + if (ret)
>> + return ret;
>> +
>> + ret = adc_channel_data(priv->adc, priv->channel, &val);
>> + if (ret)
>> + return ret;
>> +
>> + if (ret == 0)
>> + return (val >= priv->min && val < priv->max) ?
>> + BUTTON_ON : BUTTON_OFF;
>> +
>> + return ret;
>> +}
>> +
>> +static int button_adc_probe(struct udevice *dev)
>> +{
>> + struct button_uc_plat *uc_plat = dev_get_uclass_plat(dev);
>> + struct button_adc_priv *priv = dev_get_priv(dev);
>> + struct ofnode_phandle_args args;
>> + u32 treshold, up_treshold, t;
>> + unsigned int mask;
>> + ofnode node;
>> + int ret, vdd;
>> +
>> + /* Ignore the top-level button node */
>> + if (!uc_plat->label)
>> + return 0;
>> +
>> + ret = dev_read_phandle_with_args(dev->parent, "io-channels",
>> + "#io-channel-cells", 0, 0, &args);
>> + if (ret)
>> + return ret;
>> +
>> + ret = uclass_get_device_by_ofnode(UCLASS_ADC, args.node,
>> &priv->adc);
>> + if (ret)
>> + return ret;
>> +
>> + ret = ofnode_read_u32(dev_ofnode(dev->parent),
>> + "keyup-threshold-microvolt", &up_treshold);
>> + if (ret)
>> + return ret;
>> +
>> + ret = ofnode_read_u32(dev_ofnode(dev), "press-threshold-microvolt",
>> + &treshold);
>> + if (ret)
>> + return ret;
>> +
>> + dev_for_each_subnode(node, dev->parent) {
>> + ret = ofnode_read_u32(dev_ofnode(dev),
>> + "press-threshold-microvolt", &t);
>> + if (ret)
>> + return ret;
>> +
>> + if (t > treshold)
>> + up_treshold = t;
>
> Linux' Documentation/devicetree/bindings/input/adc-keys.txt describes
> that one virtual key is created per sub-node.
>
> If I read your code correctly, this is not what you are implementing.
> Instead you only define a single key per adc-keys node.
>
> Why are your deviating from the bindings document?
No I don't. button_adc_bind() binds to the root node with 'adc-keys'
compatible, while the dev_for_each_subnode() loop instantiates driver
for each subnode, so the button_adc_probe() is called for each defined
key. I've copied this pattern from gpio-keys driver.
>> ...
Here is the related code:
>> +static int button_adc_bind(struct udevice *parent)
>> +{
>> + struct udevice *dev;
>> + ofnode node;
>> + int ret;
>> +
>> + dev_for_each_subnode(node, parent) {
>> + struct button_uc_plat *uc_plat;
>> + const char *label;
>> +
>> + label = ofnode_read_string(node, "label");
>> + if (!label) {
>> + debug("%s: node %s has no label\n", __func__,
>> + ofnode_get_name(node));
>> + return -EINVAL;
>> + }
>> + ret = device_bind_driver_to_node(parent, "button_adc",
>> + ofnode_get_name(node),
>> + node, &dev);
>> + if (ret)
>> + return ret;
>> + uc_plat = dev_get_uclass_plat(dev);
>> + uc_plat->label = label;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static const struct button_ops button_adc_ops = {
>> + .get_state = button_adc_get_state,
>> +};
>> +
>> +static const struct udevice_id button_adc_ids[] = {
>> + { .compatible = "adc-keys" },
>> + { }
>> +};
>> +
>> +U_BOOT_DRIVER(button_adc) = {
>> + .name = "button_adc",
>> + .id = UCLASS_BUTTON,
>> + .of_match = button_adc_ids,
>> + .ops = &button_adc_ops,
>> + .priv_auto = sizeof(struct button_adc_priv),
>> + .bind = button_adc_bind,
>> + .probe = button_adc_probe,
>> +};
>>
>
>
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
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