[PATCH v5 2/4] button: add a simple Analog to Digital Converter device based button driver
Simon Glass
sjg at chromium.org
Mon Feb 1 21:38:55 CET 2021
Hi,
On Tue, 26 Jan 2021 at 06:03, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>
> On 26.01.21 12:25, Marek Szyprowski wrote:
> > 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:
>
> Thanks for pointing this out.
>
> To really test the driver we would need an emulated device on the
> sandbox where we can set the voltage and see which button is activated.
>
> I assume this can be added to test/dm/adc.c.
Yes please!
Regards,
Simon
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