Re: [PATCH 3/3] iio: proximity: Add a ChromeOS EC MKBP proximity driver

[Jonathan Cameron <jic23@kernel.org>]

On Fri, 22 Jan 2021 14:54:43 -0800
Stephen Boyd <swboyd@chromium.org> wrote:

> Add support for a ChromeOS EC proximity driver that exposes a "front"
> proximity sensor via the IIO subsystem. The EC decides when front
> proximity is near and sets an MKBP switch 'EC_MKBP_FRONT_PROXIMITY' to
> notify the kernel of proximity. Similarly, when proximity detects
> something far away it sets the switch bit to 0. For now this driver
> exposes a single sensor, but it could be expanded in the future via more
> MKBP bits if desired.
> 
> Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> Cc: Benson Leung <bleung@chromium.org>
> Cc: Guenter Roeck <groeck@chromium.org>
> Cc: Douglas Anderson <dianders@chromium.org>
> Cc: Gwendal Grignou <gwendal@chromium.org>
> Signed-off-by: Stephen Boyd <swboyd@chromium.org>

Hi Stephen,

Looks more or less fine to me.  My main concern is potential confusion
in naming with the cros_ec_prox_light driver that we already have.

A few other minor bits and bobs inline.

thanks,

Jonathan


> ---
>  drivers/iio/proximity/Kconfig             |  11 +
>  drivers/iio/proximity/Makefile            |   1 +
>  drivers/iio/proximity/cros_ec_proximity.c | 252 ++++++++++++++++++++++
>  3 files changed, 264 insertions(+)
>  create mode 100644 drivers/iio/proximity/cros_ec_proximity.c
> 
> diff --git a/drivers/iio/proximity/Kconfig b/drivers/iio/proximity/Kconfig
> index 12672a0e89ed..35a04e9ede7d 100644
> --- a/drivers/iio/proximity/Kconfig
> +++ b/drivers/iio/proximity/Kconfig
> @@ -21,6 +21,17 @@ endmenu
>  
>  menu "Proximity and distance sensors"
>  
> +config CROS_EC_PROXIMITY
> +	tristate "ChromeOS EC MKBP Proximity sensor"
> +	depends on CROS_EC
> +	help
> +	  Say Y here to enable the proximity sensor implemented via the ChromeOS EC MKBP
> +	  switches protocol. You must enable one bus option (CROS_EC_I2C or CROS_EC_SPI)
> +	  to use this.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called cros_ec_prox.
> +
>  config ISL29501
>  	tristate "Intersil ISL29501 Time Of Flight sensor"
>  	depends on I2C
> diff --git a/drivers/iio/proximity/Makefile b/drivers/iio/proximity/Makefile
> index 9c1aca1a8b79..b1330dd8e212 100644
> --- a/drivers/iio/proximity/Makefile
> +++ b/drivers/iio/proximity/Makefile
> @@ -5,6 +5,7 @@
>  
>  # When adding new entries keep the list in alphabetical order
>  obj-$(CONFIG_AS3935)		+= as3935.o
> +obj-$(CONFIG_CROS_EC_PROXIMITY)	+= cros_ec_proximity.o
>  obj-$(CONFIG_ISL29501)		+= isl29501.o
>  obj-$(CONFIG_LIDAR_LITE_V2)	+= pulsedlight-lidar-lite-v2.o
>  obj-$(CONFIG_MB1232)		+= mb1232.o
> diff --git a/drivers/iio/proximity/cros_ec_proximity.c b/drivers/iio/proximity/cros_ec_proximity.c
> new file mode 100644
> index 000000000000..a3aef911e3cc
> --- /dev/null
> +++ b/drivers/iio/proximity/cros_ec_proximity.c
> @@ -0,0 +1,252 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Driver for cros-ec proximity sensor exposed through MKBP switch
> + *
> + * Copyright 2021 Google LLC.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/kernel.h>

Slight preference for alphabetical order though keeping specific
sections separate as done here is fine.

> +#include <linux/notifier.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +#include <linux/types.h>
> +
> +#include <linux/platform_data/cros_ec_commands.h>
> +#include <linux/platform_data/cros_ec_proto.h>
> +
> +#include <linux/iio/events.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +
> +#include <asm/unaligned.h>
> +
> +struct cros_ec_proximity_data {
> +	struct cros_ec_device *ec;
> +	struct iio_dev *indio_dev;
> +	struct mutex lock;
> +	struct notifier_block notifier;
> +	bool enabled;
> +};
> +
> +static const struct iio_event_spec cros_ec_prox_events[] = {
> +	{
> +		.type = IIO_EV_TYPE_THRESH,
> +		.dir = IIO_EV_DIR_EITHER,
> +		.mask_separate = BIT(IIO_EV_INFO_ENABLE),
> +	},
> +};
> +
> +static const struct iio_chan_spec cros_ec_prox_chan_spec[] = {
> +	{
> +		.type = IIO_PROXIMITY,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
> +		.event_spec = cros_ec_prox_events,
> +		.num_event_specs = ARRAY_SIZE(cros_ec_prox_events),
> +	},
> +};
> +
> +static int cros_ec_proximity_parse_state(const void *data)
> +{
> +	u32 switches = get_unaligned_le32(data);
> +
> +	return !!(switches & BIT(EC_MKBP_FRONT_PROXIMITY));
> +}
> +
> +static int cros_ec_proximity_query(struct cros_ec_device *ec_dev, int *state)
> +{
> +	struct ec_params_mkbp_info *params;
> +	struct cros_ec_command *msg;
> +	int ret;
> +
> +	msg = kzalloc(sizeof(*msg) + max(sizeof(u32), sizeof(*params)),
> +		      GFP_KERNEL);

Given this is known at build time, perhaps better to add it to the 
iio_priv() accessed structure and avoid having to handle allocations
separately.

> +	if (!msg)
> +		return -ENOMEM;
> +
> +	msg->command = EC_CMD_MKBP_INFO;
> +	msg->version = 1;
> +	msg->outsize = sizeof(*params);
> +	msg->insize = sizeof(u32);
> +	params = (struct ec_params_mkbp_info *)msg->data;
> +	params->info_type = EC_MKBP_INFO_CURRENT;
> +	params->event_type = EC_MKBP_EVENT_SWITCH;
> +
> +	ret = cros_ec_cmd_xfer_status(ec_dev, msg);
> +	if (ret >= 0) {
> +		if (ret != sizeof(u32)) {
> +			dev_warn(ec_dev->dev, "wrong result size: %d != %zu\n",
> +				 ret, sizeof(u32));
> +			ret = -EPROTO;
> +		} else {
> +			*state = cros_ec_proximity_parse_state(msg->data);
> +			ret = 0;
If you move the allocation as suggested above, this can become

if (ret < 0)
	return ret;

if (ret != sizeof(u32)) {
	...
	return -EPROTO;
}

*state = cros_..
return 0;

Which will be neater and not as deeply nested.

> +		}
> +	}
> +
> +	kfree(msg);
> +
> +	return ret;
> +}
> +
> +static int cros_ec_proximity_notify(struct notifier_block *nb,
> +			     unsigned long queued_during_suspend, void *_ec)
> +{
> +	struct cros_ec_proximity_data *data;
> +	struct cros_ec_device *ec = _ec;
> +	u8 event_type = ec->event_data.event_type & EC_MKBP_EVENT_TYPE_MASK;
> +	void *switches = &ec->event_data.data.switches;
> +	struct iio_dev *indio_dev;
> +	s64 timestamp;
> +	int state, dir;
> +	u64 ev;
> +
> +	if (event_type == EC_MKBP_EVENT_SWITCH) {
> +		data = container_of(nb, struct cros_ec_proximity_data, notifier);
> +		indio_dev = data->indio_dev;
> +
> +		mutex_lock(&data->lock);
> +		if (data->enabled) {
> +			timestamp = iio_get_time_ns(indio_dev);
> +			state = cros_ec_proximity_parse_state(switches);
> +			dir = state ? IIO_EV_DIR_FALLING : IIO_EV_DIR_RISING;
> +
> +			ev = IIO_UNMOD_EVENT_CODE(IIO_PROXIMITY, 0,
> +						  IIO_EV_TYPE_THRESH, dir);
> +			iio_push_event(indio_dev, ev, timestamp);
> +		}
> +		mutex_unlock(&data->lock);
> +	}
> +
> +	return NOTIFY_OK;
> +}
> +
> +static int cros_ec_proximity_read_raw(struct iio_dev *indio_dev,
> +			   const struct iio_chan_spec *chan, int *val,
> +			   int *val2, long mask)
> +{
> +	struct cros_ec_proximity_data *data = iio_priv(indio_dev);
> +	struct cros_ec_device *ec = data->ec;
> +	int ret;
> +
> +	if (chan->type != IIO_PROXIMITY)
> +		return -EINVAL;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		ret = iio_device_claim_direct_mode(indio_dev);

Normally we only introduce these protections when adding the ability
to change the state from direct to buffered (which these prevent).
This driver doesn't yet support any other modes so I don't think
there is any benefit in having these.

If the aim is more local protection then should use a local lock
as the semantics fo these functions might change in future.


> +		if (ret)
> +			return ret;
> +
> +		ret = cros_ec_proximity_query(ec, val);
> +		iio_device_release_direct_mode(indio_dev);
> +		if (ret)
> +			return ret;
> +
> +		return IIO_VAL_INT;
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static int cros_ec_proximity_read_event_config(struct iio_dev *indio_dev,
> +				    const struct iio_chan_spec *chan,
> +				    enum iio_event_type type,
> +				    enum iio_event_direction dir)
> +{
> +	struct cros_ec_proximity_data *data = iio_priv(indio_dev);
> +
> +	return data->enabled;
> +}
> +
> +static int cros_ec_proximity_write_event_config(struct iio_dev *indio_dev,
> +				     const struct iio_chan_spec *chan,
> +				     enum iio_event_type type,
> +				     enum iio_event_direction dir, int state)
> +{
> +	struct cros_ec_proximity_data *data = iio_priv(indio_dev);
> +
> +	mutex_lock(&data->lock);
> +	data->enabled = state;
> +	mutex_unlock(&data->lock);
> +
> +	return 0;
> +}
> +
> +static const struct iio_info cros_ec_proximity_info = {
> +	.read_raw = cros_ec_proximity_read_raw,
> +	.read_event_config = cros_ec_proximity_read_event_config,
> +	.write_event_config = cros_ec_proximity_write_event_config,
> +};
> +
> +static int cros_ec_proximity_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct cros_ec_device *ec = dev_get_drvdata(dev->parent);
> +	struct iio_dev *indio_dev;
> +	struct cros_ec_proximity_data *data;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	data = iio_priv(indio_dev);
> +	data->ec = ec;
> +	data->indio_dev = indio_dev;
> +	mutex_init(&data->lock);
> +	platform_set_drvdata(pdev, data);
> +
> +	indio_dev->name = "cros_ec_proximity";
> +	indio_dev->dev.parent = dev;
> +	indio_dev->info = &cros_ec_proximity_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = cros_ec_prox_chan_spec;
> +	indio_dev->num_channels = ARRAY_SIZE(cros_ec_prox_chan_spec);
> +
> +	ret = devm_iio_device_register(dev, indio_dev);
> +	if (ret)
> +		return ret;
> +
> +	data->notifier.notifier_call = cros_ec_proximity_notify;
> +	ret = blocking_notifier_chain_register(&ec->event_notifier,
> +					       &data->notifier);
> +	if (ret)
> +		dev_err(dev, "cannot register notifier: %d\n", ret);
> +
> +	return ret;
> +}
> +
> +static int cros_ec_proximity_remove(struct platform_device *pdev)
> +{
> +	struct cros_ec_proximity_data *data = platform_get_drvdata(pdev);
> +	struct cros_ec_device *ec = data->ec;
> +
> +	blocking_notifier_chain_unregister(&ec->event_notifier,
> +					   &data->notifier);
> +
> +	return 0;
> +}
> +
> +#ifdef CONFIG_OF

As a general rule, we are trying to clear out protections on CONFIG_OF etc
and use of of_match_ptr() on the basis they don't really gain us anything
and prevent use of some other firmware types.  Here I guess you know what
your firmware looks like, but I'm still keen to drop it in the interests
of there being fewer places to copy it from.

It may be a good idea to give this a more specific name as well given
we already have cros-ec-prox as a platform device id from
the cros_ec_light_prox driver.


> +static const struct of_device_id cros_ec_proximity_of_match[] = {
> +	{ .compatible = "google,cros-ec-proximity" },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, cros_ec_proximity_of_match);
> +#endif
> +
> +static struct platform_driver cros_ec_proximity_driver = {
> +	.driver = {
> +		.name = "cros-ec-proximity",
> +		.of_match_table = of_match_ptr(cros_ec_proximity_of_match),
> +	},
> +	.probe = cros_ec_proximity_probe,
> +	.remove = cros_ec_proximity_remove,
> +};
> +module_platform_driver(cros_ec_proximity_driver);
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_DESCRIPTION("ChromeOS EC MKBP proximity sensor driver");