Re: [PATCH v2 2/3] iio: sps30: add support for serial interface

From: Jonathan Cameron
Date: Sun May 02 2021 - 13:37:37 EST

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In reply to: Tomasz Duszynski: "[PATCH v2 2/3] iio: sps30: add support for serial interface"
Next in thread: Tomasz Duszynski: "Re: [PATCH v2 2/3] iio: sps30: add support for serial interface"
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On Sun, 2 May 2021 15:44:30 +0200
Tomasz Duszynski <tomasz.duszynski@xxxxxxxxxxx> wrote:

> Sensor has support for both i2c and serial communication interfaces.
> Both offer very similar set of features. Minor differences don't impact
> overall functionality like doing measurements, etc.
>
> Support for i2c have already been added, this patch adds support
> for the latter ie. serial interface.
>
> Signed-off-by: Tomasz Duszynski <tomasz.duszynski@xxxxxxxxxxx>
Two trivial comments inline. I'm happy to tidy those up whilst applying if
everyone else is happy with this and you don't need to do a v3.

Thanks,

Jonathan

> ---
> MAINTAINERS | 1 +
> drivers/iio/chemical/Kconfig | 11 +
> drivers/iio/chemical/Makefile | 1 +
> drivers/iio/chemical/sps30_serial.c | 428 ++++++++++++++++++++++++++++
> 4 files changed, 441 insertions(+)
> create mode 100644 drivers/iio/chemical/sps30_serial.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 4b39a9c48736..cab9a63ad2cf 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -16138,6 +16138,7 @@ S: Maintained
> F: Documentation/devicetree/bindings/iio/chemical/sensirion,sps30.yaml
> F: drivers/iio/chemical/sps30.c
> F: drivers/iio/chemical/sps30_i2c.c
> +F: drivers/iio/chemical/sps30_serial.c
>
> SERIAL DEVICE BUS
> M: Rob Herring <robh@xxxxxxxxxx>
> diff --git a/drivers/iio/chemical/Kconfig b/drivers/iio/chemical/Kconfig
> index 2b45a76ab7bc..a4920646e9be 100644
> --- a/drivers/iio/chemical/Kconfig
> +++ b/drivers/iio/chemical/Kconfig
> @@ -148,6 +148,17 @@ config SPS30_I2C
> To compile this driver as a module, choose M here: the module will
> be called sps30_i2c.
>
> +config SPS30_SERIAL
> + tristate "SPS30 particulate matter sensor serial driver"
> + depends on SERIAL_DEV_BUS
> + select SPS30
> + help
> + Say Y here to build support for the Sensirion SPS30 serial interface
> + driver.
> +
> + To compile this driver as a module, choose M here: the module will
> + be called sps30_serial.
> +
> config VZ89X
> tristate "SGX Sensortech MiCS VZ89X VOC sensor"
> depends on I2C
> diff --git a/drivers/iio/chemical/Makefile b/drivers/iio/chemical/Makefile
> index 41c264a229c0..4898690cc155 100644
> --- a/drivers/iio/chemical/Makefile
> +++ b/drivers/iio/chemical/Makefile
> @@ -18,4 +18,5 @@ obj-$(CONFIG_SCD30_SERIAL) += scd30_serial.o
> obj-$(CONFIG_SENSIRION_SGP30) += sgp30.o
> obj-$(CONFIG_SPS30) += sps30.o
> obj-$(CONFIG_SPS30_I2C) += sps30_i2c.o
> +obj-$(CONFIG_SPS30_SERIAL) += sps30_serial.o
> obj-$(CONFIG_VZ89X) += vz89x.o
> diff --git a/drivers/iio/chemical/sps30_serial.c b/drivers/iio/chemical/sps30_serial.c
> new file mode 100644
> index 000000000000..3dc1a9e2ae82
> --- /dev/null
> +++ b/drivers/iio/chemical/sps30_serial.c
> @@ -0,0 +1,428 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Sensirion SPS30 particulate matter sensor serial driver
> + *
> + * Copyright (c) 2021 Tomasz Duszynski <tomasz.duszynski@xxxxxxxxxxx>
> + */
> +#include <linux/completion.h>
> +#include <linux/device.h>
> +#include <linux/errno.h>
> +#include <linux/iio/iio.h>
> +#include <linux/minmax.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/serdev.h>
> +#include <linux/types.h>
> +
> +#include "sps30.h"
> +
> +#define SPS30_SERIAL_DEV_NAME "sps30"
> +
> +#define SPS30_SERIAL_SOF_EOF 0x7e
> +#define SPS30_SERIAL_TIMEOUT msecs_to_jiffies(20)
> +#define SPS30_SERIAL_MAX_BUF_SIZE 263
> +#define SPS30_SERIAL_ESCAPE_CHAR 0x7d
> +
> +#define SPS30_SERIAL_FRAME_MIN_SIZE 7
> +#define SPS30_SERIAL_FRAME_ADR_OFFSET 1
> +#define SPS30_SERIAL_FRAME_CMD_OFFSET 2
> +#define SPS30_SERIAL_FRAME_MOSI_LEN_OFFSET 3
> +#define SPS30_SERIAL_FRAME_MISO_STATE_OFFSET 3
> +#define SPS30_SERIAL_FRAME_MISO_LEN_OFFSET 4
> +#define SPS30_SERIAL_FRAME_MISO_DATA_OFFSET 5
> +
> +#define SPS30_SERIAL_START_MEAS 0x00
> +#define SPS30_SERIAL_STOP_MEAS 0x01
> +#define SPS30_SERIAL_READ_MEAS 0x03
> +#define SPS30_SERIAL_RESET 0xd3
> +#define SPS30_SERIAL_CLEAN_FAN 0x56
> +#define SPS30_SERIAL_PERIOD 0x80
> +#define SPS30_SERIAL_DEV_INFO 0xd0
> +#define SPS30_SERIAL_READ_VERSION 0xd1
> +
> +struct sps30_serial_priv {
> + struct completion new_frame;
> + unsigned char buf[SPS30_SERIAL_MAX_BUF_SIZE];
> + size_t num;
> + bool escaped;
> + bool done;
> +};
> +
> +static int sps30_serial_xfer(struct sps30_state *state, const unsigned char *buf, size_t size)
> +{
> + struct serdev_device *serdev = to_serdev_device(state->dev);
> + struct sps30_serial_priv *priv = state->priv;
> + int ret;
> +
> + priv->num = 0;
> + priv->escaped = false;
> + priv->done = false;
> +
> + ret = serdev_device_write(serdev, buf, size, SPS30_SERIAL_TIMEOUT);
> + if (ret < 0)
> + return ret;
> + if (ret != size)
> + return -EIO;
> +
> + ret = wait_for_completion_interruptible_timeout(&priv->new_frame, SPS30_SERIAL_TIMEOUT);
> + if (ret < 0)
> + return ret;
> + if (!ret)
> + return -ETIMEDOUT;
> +
> + return 0;
> +}
> +
> +static struct {
> + unsigned char byte;
> + unsigned char byte2;
> +} sps30_serial_bytes[] = {
> + { 0x11, 0x31 },
> + { 0x13, 0x33 },
> + { 0x7e, 0x5e },
> + { 0x7d, 0x5d },
> +};

const?

> +
> +static int sps30_serial_put_byte(unsigned char *buf, unsigned char byte)
> +{
> + int i;
> +
> + for (i = 0; i < ARRAY_SIZE(sps30_serial_bytes); i++) {
> + if (sps30_serial_bytes[i].byte != byte)
> + continue;
> +
> + buf[0] = SPS30_SERIAL_ESCAPE_CHAR;
> + buf[1] = sps30_serial_bytes[i].byte2;
> +
> + return 2;
> + }
> +
> + buf[0] = byte;
> +
> + return 1;
> +}
> +
> +static char sps30_serial_get_byte(bool escaped, unsigned char byte2)
> +{
> + int i;
> +
> + if (!escaped)
> + return byte2;
> +
> + for (i = 0; i < ARRAY_SIZE(sps30_serial_bytes); i++) {
> + if (sps30_serial_bytes[i].byte2 != byte2)
> + continue;
> +
> + return sps30_serial_bytes[i].byte;
> + }
> +
> + return 0;
> +}
> +
> +static unsigned char sps30_serial_calc_chksum(const unsigned char *buf, size_t num)
> +{
> + unsigned int chksum = 0;
> + size_t i;
> +
> + for (i = 0; i < num; i++)
> + chksum += buf[i];
> +
> + return ~chksum;
> +}
> +
> +static int sps30_serial_prep_frame(unsigned char *buf, unsigned char cmd,
> + const unsigned char *arg, size_t arg_size)
> +{
> + unsigned char chksum;
> + int num = 0;
> + size_t i;
> +
> + buf[num++] = SPS30_SERIAL_SOF_EOF;
> + buf[num++] = 0;
> + num += sps30_serial_put_byte(buf + num, cmd);
> + num += sps30_serial_put_byte(buf + num, arg_size);
> +
> + for (i = 0; i < arg_size; i++)
> + num += sps30_serial_put_byte(buf + num, arg[i]);
> +
> + /* SOF isn't checksummed */
> + chksum = sps30_serial_calc_chksum(buf + 1, num - 1);
> + num += sps30_serial_put_byte(buf + num, chksum);
> + buf[num++] = SPS30_SERIAL_SOF_EOF;
> +
> + return num;
> +}
> +
> +static bool sps30_serial_frame_valid(struct sps30_state *state, const unsigned char *buf)
> +{
> + struct sps30_serial_priv *priv = state->priv;
> + unsigned char chksum;
> +
> + if ((priv->num < SPS30_SERIAL_FRAME_MIN_SIZE) ||
> + (priv->num != SPS30_SERIAL_FRAME_MIN_SIZE +
> + priv->buf[SPS30_SERIAL_FRAME_MISO_LEN_OFFSET])) {
> + dev_err(state->dev, "frame has invalid number of bytes\n");
> + return false;
> + }
> +
> + if ((priv->buf[SPS30_SERIAL_FRAME_ADR_OFFSET] != buf[SPS30_SERIAL_FRAME_ADR_OFFSET]) ||
> + (priv->buf[SPS30_SERIAL_FRAME_CMD_OFFSET] != buf[SPS30_SERIAL_FRAME_CMD_OFFSET])) {
> + dev_err(state->dev, "frame has wrong ADR and CMD bytes\n");
> + return false;
> + }
> +
> + if (priv->buf[SPS30_SERIAL_FRAME_MISO_STATE_OFFSET]) {
> + dev_err(state->dev, "frame with non-zero state received (0x%02x)\n",
> + priv->buf[SPS30_SERIAL_FRAME_MISO_STATE_OFFSET]);
> + return false;
> + }
> +
> + /* SOF, checksum and EOF are not checksummed */
> + chksum = sps30_serial_calc_chksum(priv->buf + 1, priv->num - 3);
> + if (priv->buf[priv->num - 2] != chksum) {
> + dev_err(state->dev, "frame integrity check failed\n");
> + return false;
> + }
> +
> + return true;
> +}
> +
> +static int sps30_serial_command(struct sps30_state *state, unsigned char cmd,
> + const void *arg, size_t arg_size, void *rsp, size_t rsp_size)
> +{
> + struct sps30_serial_priv *priv = state->priv;
> + unsigned char buf[SPS30_SERIAL_MAX_BUF_SIZE];
> + int ret, size;
> +
> + size = sps30_serial_prep_frame(buf, cmd, arg, arg_size);
> + ret = sps30_serial_xfer(state, buf, size);
> + if (ret)
> + return ret;
> +
> + if (!sps30_serial_frame_valid(state, buf))
> + return -EIO;
> +
> + if (rsp) {
> + rsp_size = min_t(size_t, priv->buf[SPS30_SERIAL_FRAME_MISO_LEN_OFFSET], rsp_size);
> + memcpy(rsp, &priv->buf[SPS30_SERIAL_FRAME_MISO_DATA_OFFSET], rsp_size);
> + }
> +
> + return rsp_size;
> +}
> +
> +static int sps30_serial_receive_buf(struct serdev_device *serdev,
> + const unsigned char *buf, size_t size)
> +{
> + struct iio_dev *indio_dev = dev_get_drvdata(&serdev->dev);
> + struct sps30_serial_priv *priv;
> + struct sps30_state *state;
> + unsigned char byte;
> + size_t i;
> +
> + if (!indio_dev)
> + return 0;
> +
> + state = iio_priv(indio_dev);
> + priv = state->priv;
> +
> + /* just in case device put some unexpected data on the bus */
> + if (priv->done)
> + return size;
> +
> + /* wait for the start of frame */
> + if (!priv->num && size && buf[0] != SPS30_SERIAL_SOF_EOF)
> + return 1;
> +
> + if (priv->num + size >= ARRAY_SIZE(priv->buf))
> + size = ARRAY_SIZE(priv->buf) - priv->num;
> +
> + for (i = 0; i < size; i++) {
> + byte = buf[i];
> + /* remove stuffed bytes on-the-fly */
> + if (byte == SPS30_SERIAL_ESCAPE_CHAR) {
> + priv->escaped = true;
> + continue;
> + }
> +
> + byte = sps30_serial_get_byte(priv->escaped, byte);
> + if (priv->escaped && !byte)
> + dev_warn(state->dev, "unrecognized escaped char (0x%02x)\n", byte);
> +
> + priv->buf[priv->num++] = byte;
> +
> + /* EOF received */
> + if (!priv->escaped && byte == SPS30_SERIAL_SOF_EOF) {
> + if (priv->num < SPS30_SERIAL_FRAME_MIN_SIZE)
> + continue;
> +
> + priv->done = true;
> + complete(&priv->new_frame);
> + i++;
> + break;
> + }
> +
> + priv->escaped = false;
> + }
> +
> + return i;
> +}
> +
> +static const struct serdev_device_ops sps30_serial_device_ops = {
> + .receive_buf = sps30_serial_receive_buf,
> + .write_wakeup = serdev_device_write_wakeup,
> +};
> +
> +static int sps30_serial_start_meas(struct sps30_state *state)
> +{
> + /* request BE IEEE754 formatted data */
> + unsigned char buf[] = { 0x01, 0x03 };
> +
> + return sps30_serial_command(state, SPS30_SERIAL_START_MEAS, buf, sizeof(buf), NULL, 0);
> +}
> +
> +static int sps30_serial_stop_meas(struct sps30_state *state)
> +{
> + return sps30_serial_command(state, SPS30_SERIAL_STOP_MEAS, NULL, 0, NULL, 0);
> +}
> +
> +static int sps30_serial_reset(struct sps30_state *state)
> +{
> + int ret;
> +
> + ret = sps30_serial_command(state, SPS30_SERIAL_RESET, NULL, 0, NULL, 0);
> + msleep(500);
> +
> + return ret;
> +}
> +
> +static int sps30_serial_read_meas(struct sps30_state *state, __be32 *meas, size_t num)
> +{
> + int ret;
> +
> + /* measurements are ready within a second */
> + if (msleep_interruptible(1000))
> + return -EINTR;
> +
> + ret = sps30_serial_command(state, SPS30_SERIAL_READ_MEAS, NULL, 0, meas, num * sizeof(num));
> + if (ret < 0)
> + return ret;
> + /* if measurements aren't ready sensor returns empty frame */
> + if (ret == SPS30_SERIAL_FRAME_MIN_SIZE)
> + return -ETIMEDOUT;
> + if (ret != num * sizeof(*meas))
> + return -EIO;
> +
> + return 0;
> +}
> +
> +static int sps30_serial_clean_fan(struct sps30_state *state)
> +{
> + return sps30_serial_command(state, SPS30_SERIAL_CLEAN_FAN, NULL, 0, NULL, 0);
> +}
> +
> +static int sps30_serial_read_cleaning_period(struct sps30_state *state, __be32 *period)
> +{
> + unsigned char buf[] = { 0x00 };
> + int ret;
> +
> + ret = sps30_serial_command(state, SPS30_SERIAL_PERIOD, buf, sizeof(buf),
> + period, sizeof(*period));
> + if (ret < 0)
> + return ret;
> + if (ret != sizeof(*period))
> + return -EIO;
> +
> + return 0;
> +}
> +
> +static int sps30_serial_write_cleaning_period(struct sps30_state *state, __be32 period)
> +{
> + unsigned char buf[5] = { 0x00 };
> +
> + memcpy(buf + 1, &period, sizeof(period));
> +
> + return sps30_serial_command(state, SPS30_SERIAL_PERIOD, buf, sizeof(buf), NULL, 0);
> +}
> +
> +static int sps30_serial_show_info(struct sps30_state *state)
> +{
> + /* extra nul byte just in case serial number isn't a valid string */
> + unsigned char buf[32 + 1] = { 0x00 };
> + struct device *dev = state->dev;
> + int ret;
> +
> + /* tell device to return serial number */
> + buf[0] = 0x03;

Bit odd when you just set it to 0 above. Maybe just set
unsigned char buf[32 + 1] = { 0x03 }; and combine the comments?

If everything else is fine, I can do that whilst applying.

> + ret = sps30_serial_command(state, SPS30_SERIAL_DEV_INFO, buf, 1, buf, sizeof(buf) - 1);
> + if (ret < 0)
> + return ret;
> +
> + dev_info(dev, "serial number: %s\n", buf);
> +
> + ret = sps30_serial_command(state, SPS30_SERIAL_READ_VERSION, NULL, 0, buf, sizeof(buf) - 1);
> + if (ret < 0)
> + return ret;
> + if (ret < 2)
> + return -EIO;
> +
> + dev_info(dev, "fw version: %u.%u\n", buf[0], buf[1]);
> +
> + return 0;
> +}
> +
> +static const struct sps30_ops sps30_serial_ops = {
> + .start_meas = sps30_serial_start_meas,
> + .stop_meas = sps30_serial_stop_meas,
> + .read_meas = sps30_serial_read_meas,
> + .reset = sps30_serial_reset,
> + .clean_fan = sps30_serial_clean_fan,
> + .read_cleaning_period = sps30_serial_read_cleaning_period,
> + .write_cleaning_period = sps30_serial_write_cleaning_period,
> + .show_info = sps30_serial_show_info,
> +};
> +
> +static int sps30_serial_probe(struct serdev_device *serdev)
> +{
> + struct device *dev = &serdev->dev;
> + struct sps30_serial_priv *priv;
> + int ret;
> +
> + priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> + if (!priv)
> + return -ENOMEM;
> +
> + init_completion(&priv->new_frame);
> + serdev_device_set_client_ops(serdev, &sps30_serial_device_ops);
> +
> + ret = devm_serdev_device_open(dev, serdev);
> + if (ret)
> + return ret;
> +
> + serdev_device_set_baudrate(serdev, 115200);
> + serdev_device_set_flow_control(serdev, false);
> +
> + ret = serdev_device_set_parity(serdev, SERDEV_PARITY_NONE);
> + if (ret)
> + return ret;
> +
> + return sps30_probe(dev, SPS30_SERIAL_DEV_NAME, priv, &sps30_serial_ops);
> +}
> +
> +static const struct of_device_id sps30_serial_of_match[] = {
> + { .compatible = "sensirion,sps30" },
> + { }
> +};
> +MODULE_DEVICE_TABLE(of, sps30_serial_of_match);
> +
> +static struct serdev_device_driver sps30_serial_driver = {
> + .driver = {
> + .name = KBUILD_MODNAME,
> + .of_match_table = sps30_serial_of_match,
> + },
> + .probe = sps30_serial_probe,
> +};
> +module_serdev_device_driver(sps30_serial_driver);
> +
> +MODULE_AUTHOR("Tomasz Duszynski <tomasz.duszynski@xxxxxxxxxxx>");
> +MODULE_DESCRIPTION("Sensirion SPS30 particulate matter sensor serial driver");
> +MODULE_LICENSE("GPL v2");

Next message: Jonathan Cameron: "Re: [PATCH v3 0/2] staging: iio: cdc: ad7746: add dt properties for capacitive channel setup"
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