[PATCH v5 2/4] button: add a simple Analog to Digital Converter device based button driver

[Marek Szyprowski <m.szyprowski@samsung.com>]

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@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@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@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