Re: [PATCH v2 3/4] iio: chemical: scd30: add serial interface driver

From: Tomasz Duszynski
Date: Sun May 31 2020 - 11:52:39 EST

On Sun, May 31, 2020 at 11:15:18AM +0100, Jonathan Cameron wrote:
> On Sat, 30 May 2020 23:36:29 +0200
> Tomasz Duszynski <tomasz.duszynski@xxxxxxxxxxx> wrote:
>
> > Add serial interface driver for the SCD30 sensor.
> >
> > Signed-off-by: Tomasz Duszynski <tomasz.duszynski@xxxxxxxxxxx>
>
> Ah Now I see why you had those extra elements in the iio_priv
> structure.
>

Indeed. That the whole point of having them. I'll add a short
explanation what those elements are for.

> Hmm. serdev_device callbacks using the top level device drvdata
> is a bit annoying. Really feels to me like they should have
> their own priv data for those callbacks given the device
> drvdata gets used for so many other things.
>
> Oh well. Guess this is the best we can do!
>
> Jonathan
>
> > ---
> > MAINTAINERS | 1 +
> > drivers/iio/chemical/Kconfig | 11 ++
> > drivers/iio/chemical/Makefile | 1 +
> > drivers/iio/chemical/scd30_serial.c | 266 ++++++++++++++++++++++++++++
> > 4 files changed, 279 insertions(+)
> > create mode 100644 drivers/iio/chemical/scd30_serial.c
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 13aed3473b7e..5db4b446c8ba 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -15143,6 +15143,7 @@ S: Maintained
> > F: drivers/iio/chemical/scd30.h
> > F: drivers/iio/chemical/scd30_core.c
> > F: drivers/iio/chemical/scd30_i2c.c
> > +F: drivers/iio/chemical/scd30_serial.c
> >
> > SENSIRION SPS30 AIR POLLUTION SENSOR DRIVER
> > M: Tomasz Duszynski <tduszyns@xxxxxxxxx>
> > diff --git a/drivers/iio/chemical/Kconfig b/drivers/iio/chemical/Kconfig
> > index 970d34888c2e..10bb431bc3ce 100644
> > --- a/drivers/iio/chemical/Kconfig
> > +++ b/drivers/iio/chemical/Kconfig
> > @@ -107,6 +107,17 @@ config SCD30_I2C
> > To compile this driver as a module, choose M here: the module will
> > be called scd30_i2c.
> >
> > +config SCD30_SERIAL
> > + tristate "SCD30 carbon dioxide sensor serial driver"
> > + depends on SCD30_CORE && SERIAL_DEV_BUS
> > + select CRC16
> > + help
> > + Say Y here to build support for the Sensirion SCD30 serial interface
> > + driver.
> > +
> > + To compile this driver as a module, choose M here: the module will
> > + be called scd30_serial.
> > +
> > config SENSIRION_SGP30
> > tristate "Sensirion SGPxx gas sensors"
> > depends on I2C
> > diff --git a/drivers/iio/chemical/Makefile b/drivers/iio/chemical/Makefile
> > index 0966ca34e34b..fef63dd5bf92 100644
> > --- a/drivers/iio/chemical/Makefile
> > +++ b/drivers/iio/chemical/Makefile
> > @@ -14,6 +14,7 @@ obj-$(CONFIG_IAQCORE) += ams-iaq-core.o
> > obj-$(CONFIG_PMS7003) += pms7003.o
> > obj-$(CONFIG_SCD30_CORE) += scd30_core.o
> > obj-$(CONFIG_SCD30_I2C) += scd30_i2c.o
> > +obj-$(CONFIG_SCD30_SERIAL) += scd30_serial.o
> > obj-$(CONFIG_SENSIRION_SGP30) += sgp30.o
> > obj-$(CONFIG_SPS30) += sps30.o
> > obj-$(CONFIG_VZ89X) += vz89x.o
> > diff --git a/drivers/iio/chemical/scd30_serial.c b/drivers/iio/chemical/scd30_serial.c
> > new file mode 100644
> > index 000000000000..07d7d3110fe0
> > --- /dev/null
> > +++ b/drivers/iio/chemical/scd30_serial.c
> > @@ -0,0 +1,266 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Sensirion SCD30 carbon dioxide sensor serial driver
> > + *
> > + * Copyright (c) 2020 Tomasz Duszynski <tomasz.duszynski@xxxxxxxxxxx>
> > + */
> > +#include <linux/crc16.h>
> > +#include <linux/device.h>
> > +#include <linux/errno.h>
> > +#include <linux/iio/iio.h>
> > +#include <linux/jiffies.h>
> > +#include <linux/mod_devicetable.h>
> > +#include <linux/module.h>
> > +#include <linux/property.h>
> > +#include <linux/serdev.h>
> > +#include <linux/string.h>
> > +#include <linux/types.h>
> > +#include <asm/unaligned.h>
> > +
> > +#include "scd30.h"
> > +
> > +#define SCD30_SERDEV_ADDR 0x61
> > +#define SCD30_SERDEV_WRITE 0x06
> > +#define SCD30_SERDEV_READ 0x03
> > +#define SCD30_SERDEV_MAX_BUF_SIZE 17
> > +#define SCD30_SERDEV_RX_HEADER_SIZE 3
> > +#define SCD30_SERDEV_CRC_SIZE 2
> > +#define SCD30_SERDEV_TIMEOUT msecs_to_jiffies(200)
> > +
> > +struct scd30_serdev_priv {
> > + struct completion meas_ready;
> > + char *buf;
> > + int num_expected;
> > + int num;
> > +};
> > +
> > +static u16 scd30_serdev_cmd_lookup_tbl[] = {
> > + [CMD_START_MEAS] = 0x0036,
> > + [CMD_STOP_MEAS] = 0x0037,
> > + [CMD_MEAS_INTERVAL] = 0x0025,
> > + [CMD_MEAS_READY] = 0x0027,
> > + [CMD_READ_MEAS] = 0x0028,
> > + [CMD_ASC] = 0x003a,
> > + [CMD_FRC] = 0x0039,
> > + [CMD_TEMP_OFFSET] = 0x003b,
> > + [CMD_FW_VERSION] = 0x0020,
> > + [CMD_RESET] = 0x0034,
> > +};
> > +
> > +static u16 scd30_serdev_calc_crc(const char *buf, int size)
> > +{
> > + return crc16(0xffff, buf, size);
> > +}
> > +
> > +static int scd30_serdev_xfer(struct scd30_state *state, char *txbuf, int txsize,
> > + char *rxbuf, int rxsize)
> > +{
> > + struct serdev_device *serdev = to_serdev_device(state->dev);
> > + struct scd30_serdev_priv *priv = state->priv;
> > + int ret;
> > +
> > + priv->buf = rxbuf;
> > + priv->num_expected = rxsize;
> > + priv->num = 0;
> > +
> > + ret = serdev_device_write(serdev, txbuf, txsize, SCD30_SERDEV_TIMEOUT);
> > + if (ret < txsize)
> > + return ret < 0 ? ret : -EIO;
> > +
> > + ret = wait_for_completion_interruptible_timeout(&priv->meas_ready,
> > + SCD30_SERDEV_TIMEOUT);
> > + if (ret > 0)
> > + ret = 0;
> > + else if (!ret)
> > + ret = -ETIMEDOUT;
> > +
> > + return ret;
> > +}
> > +
> > +static int scd30_serdev_command(struct scd30_state *state, enum scd30_cmd cmd,
> > + u16 arg, void *response, int size)
> > +{
> > + /*
> > + * Communication over serial line is based on modbus protocol (or rather
> > + * its variation called modbus over serial to be precise). Upon
> > + * receiving a request device should reply with response.
> > + *
> > + * Frame below represents a request message. Each field takes
> > + * exactly one byte.
> > + *
> > + * +------+------+-----+-----+-------+-------+-----+-----+
> > + * | dev | op | reg | reg | byte1 | byte0 | crc | crc |
> > + * | addr | code | msb | lsb | | | lsb | msb |
> > + * +------+------+-----+-----+-------+-------+-----+-----+
> > + *
> > + * The message device replies with depends on the 'op code' field from
> > + * the request. In case it was set to SCD30_SERDEV_WRITE sensor should
> > + * reply with unchanged request. Otherwise 'op code' was set to
> > + * SCD30_SERDEV_READ and response looks like the one below. As with
> > + * request, each field takes one byte.
> > + *
> > + * +------+------+--------+-------+-----+-------+-----+-----+
> > + * | dev | op | num of | byte0 | ... | byteN | crc | crc |
> > + * | addr | code | bytes | | | | lsb | msb |
> > + * +------+------+--------+-------+-----+-------+-----+-----+
> > + */
> > + char txbuf[SCD30_SERDEV_MAX_BUF_SIZE] = { SCD30_SERDEV_ADDR },
> > + rxbuf[SCD30_SERDEV_MAX_BUF_SIZE], *rsp = response;
> > + int ret, rxsize, txsize = 2;
> > + u16 crc;
> > +
> > + put_unaligned_be16(scd30_serdev_cmd_lookup_tbl[cmd], txbuf + txsize);
> > + txsize += 2;
> > +
> > + if (rsp) {
> > + txbuf[1] = SCD30_SERDEV_READ;
> > + if (cmd == CMD_READ_MEAS)
> > + /* number of u16 words to read */
> > + put_unaligned_be16(size / 2, txbuf + txsize);
> > + else
> > + put_unaligned_be16(0x0001, txbuf + txsize);
> > + txsize += 2;
> > + crc = scd30_serdev_calc_crc(txbuf, txsize);
> > + put_unaligned_le16(crc, txbuf + txsize);
> > + txsize += 2;
> > + rxsize = SCD30_SERDEV_RX_HEADER_SIZE + size +
> > + SCD30_SERDEV_CRC_SIZE;
> > + } else {
> > + if ((cmd == CMD_STOP_MEAS) || (cmd == CMD_RESET))
> > + arg = 0x0001;
> > +
> > + txbuf[1] = SCD30_SERDEV_WRITE;
> > + put_unaligned_be16(arg, txbuf + txsize);
> > + txsize += 2;
> > + crc = scd30_serdev_calc_crc(txbuf, txsize);
> > + put_unaligned_le16(crc, txbuf + txsize);
> > + txsize += 2;
> > + rxsize = txsize;
> > + }
> > +
> > + ret = scd30_serdev_xfer(state, txbuf, txsize, rxbuf, rxsize);
> > + if (ret)
> > + return ret;
> > +
> > + switch (txbuf[1]) {
> > + case SCD30_SERDEV_WRITE:
> > + if (memcmp(txbuf, txbuf, txsize)) {
> > + dev_err(state->dev, "wrong message received\n");
> > + return -EIO;
> > + }
> > + break;
> > + case SCD30_SERDEV_READ:
> > + if (rxbuf[2] != (rxsize -
> > + SCD30_SERDEV_RX_HEADER_SIZE -
> > + SCD30_SERDEV_CRC_SIZE)) {
> > + dev_err(state->dev,
> > + "received data size does not match header\n");
> > + return -EIO;
> > + }
> > +
> > + rxsize -= SCD30_SERDEV_CRC_SIZE;
> > + crc = get_unaligned_le16(rxbuf + rxsize);
> > + if (crc != scd30_serdev_calc_crc(rxbuf, rxsize)) {
> > + dev_err(state->dev, "data integrity check failed\n");
> > + return -EIO;
> > + }
> > +
> > + rxsize -= SCD30_SERDEV_RX_HEADER_SIZE;
> > + memcpy(rsp, rxbuf + SCD30_SERDEV_RX_HEADER_SIZE, rxsize);
> > + break;
> > + default:
> > + dev_err(state->dev, "received unknown op code\n");
> > + return -EIO;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static int scd30_serdev_receive_buf(struct serdev_device *serdev,
> > + const unsigned char *buf, size_t size)
> > +{
> > + struct iio_dev *indio_dev = dev_get_drvdata(&serdev->dev);
> > + struct scd30_serdev_priv *priv;
> > + struct scd30_state *state;
> > + int num;
> > +
> > + if (!indio_dev)
> > + return 0;
> > +
> > + state = iio_priv(indio_dev);
> > + priv = state->priv;
> > +
> > + /* just in case sensor puts some unexpected bytes on the bus */
> > + if (!priv->buf)
> > + return 0;
> > +
> > + if (priv->num + size >= priv->num_expected)
> > + num = priv->num_expected - priv->num;
> > + else
> > + num = size;
> > +
> > + memcpy(priv->buf + priv->num, buf, num);
> > + priv->num += num;
> > +
> > + if (priv->num == priv->num_expected) {
> > + priv->buf = NULL;
> > + complete(&priv->meas_ready);
> > + }
> > +
> > + return num;
> > +}
> > +
> > +static const struct serdev_device_ops scd30_serdev_ops = {
> > + .receive_buf = scd30_serdev_receive_buf,
> > + .write_wakeup = serdev_device_write_wakeup,
> > +};
> > +
> > +static int scd30_serdev_probe(struct serdev_device *serdev)
> > +{
> > + struct device *dev = &serdev->dev;
> > + struct scd30_serdev_priv *priv;
> > + int irq, ret;
> > +
> > + priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> > + if (!priv)
> > + return -ENOMEM;
> > +
> > + init_completion(&priv->meas_ready);
> > + serdev_device_set_client_ops(serdev, &scd30_serdev_ops);
> > +
> > + ret = devm_serdev_device_open(dev, serdev);
> > + if (ret)
> > + return ret;
> > +
> > + serdev_device_set_baudrate(serdev, 19200);
> > + serdev_device_set_flow_control(serdev, false);
> > +
> > + ret = serdev_device_set_parity(serdev, SERDEV_PARITY_NONE);
> > + if (ret)
> > + return ret;
> > +
> > + irq = fwnode_irq_get(dev_fwnode(dev), 0);
> > +
> > + return scd30_probe(dev, irq, KBUILD_MODNAME, priv,
> > + scd30_serdev_command);
> > +}
> > +
> > +static const struct of_device_id scd30_serdev_of_match[] = {
> > + { .compatible = "sensirion,scd30" },
> > + { }
> > +};
> > +MODULE_DEVICE_TABLE(of, scd30_serdev_of_match);
> > +
> > +static struct serdev_device_driver scd30_serdev_driver = {
> > + .driver = {
> > + .name = KBUILD_MODNAME,
> > + .of_match_table = scd30_serdev_of_match,
> > + .pm = &scd30_pm_ops,
> > + },
> > + .probe = scd30_serdev_probe,
> > +};
> > +module_serdev_device_driver(scd30_serdev_driver);
> > +
> > +MODULE_AUTHOR("Tomasz Duszynski <tomasz.duszynski@xxxxxxxxxxx>");
> > +MODULE_DESCRIPTION("Sensirion SCD30 carbon dioxide sensor serial driver");
> > +MODULE_LICENSE("GPL v2");
>