| Message ID | 20240826125803.71970-1-apokusinski01@gmail.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | [v3] hwmon: (sht4x): add heater support | expand |
On 8/26/24 05:58, Antoni Pokusinski wrote: > Add support for manipulating the internal heater of sht4x devices. > Enabling the heater removes condensed water from the sensor surface > which disturbs the relative humidity measurements. > > The heater can operate at three heating levels (20, 110 or 200 > milliwatts). Also, two heating durations may be selected (0.1 or 1s). > Once the heating time elapses the heater is automatically switched off. > > Signed-off-by: Antoni Pokusinski <apokusinski01@gmail.com> > --- > Hello Guenter, > > Thanks for the review. > I'm not sure if this short patch description above is now ok or shall I > be even more detailed. > The problem that I was facing was that when I was using the sensor for > relative humidity measurements the results were always ~100% even though > the correct value should be ~60%. Enabling the heater in periodic pulses > to remove the condensation fixed the issue and the measurements were > correct after that. > Thus, I'm not sure if I should include that detailed arguments in the > patch description or leave it as it is right now. > > Regards, > Antoni Pokusinski > > -- > Changes since v2: > * heater_enable_store: remove unnecessary if > * Documentation: remove incorrect info about turning off the heater > * be more specific in the patch description > > Changes since v1: > * explain the use case of the new attributes set > * heater_enable attr: make it write-only > * heater_enable_store: define cmd as u8 instead of u8* > * heater_enable_store: remove unreachable data path > * heater_enable_store: remove unnecessary lock > * heater_enable_store: call i2c_master_send only if status==true > * define attributes as DEVICE_ATTR_* instead of SENSOR_DEVICE_ATTR_* > --- > Documentation/hwmon/sht4x.rst | 10 +++ > drivers/hwmon/sht4x.c | 126 +++++++++++++++++++++++++++++++++- > 2 files changed, 135 insertions(+), 1 deletion(-) > > diff --git a/Documentation/hwmon/sht4x.rst b/Documentation/hwmon/sht4x.rst > index daf21e763425..0b17f89fa1ab 100644 > --- a/Documentation/hwmon/sht4x.rst > +++ b/Documentation/hwmon/sht4x.rst > @@ -42,4 +42,14 @@ humidity1_input Measured humidity in %H > update_interval The minimum interval for polling the sensor, > in milliseconds. Writable. Must be at least > 2000. > +heater_power The requested heater power, in milliwatts. > + Available values: 20, 110, 200 (default: 200). > +heater_time The requested operating time of the heater, > + in milliseconds. > + Available values: 100, 1000 (default 1000). > +heater_enable Enable the heater with the selected power > + and for the selected time in order to remove > + condensed water from the sensor surface. Write-only. > + > + - 1: turn on > =============== ============================================ > diff --git a/drivers/hwmon/sht4x.c b/drivers/hwmon/sht4x.c > index b8916d2735b5..20b50f7feac0 100644 > --- a/drivers/hwmon/sht4x.c > +++ b/drivers/hwmon/sht4x.c > @@ -11,6 +11,7 @@ > #include <linux/crc8.h> > #include <linux/delay.h> > #include <linux/hwmon.h> > +#include <linux/hwmon-sysfs.h> > #include <linux/i2c.h> > #include <linux/jiffies.h> > #include <linux/module.h> > @@ -31,6 +32,12 @@ > */ > #define SHT4X_CMD_MEASURE_HPM 0b11111101 > #define SHT4X_CMD_RESET 0b10010100 > +#define SHT4X_CMD_HEATER_20_1 0b00011110 > +#define SHT4X_CMD_HEATER_20_01 0b00010101 > +#define SHT4X_CMD_HEATER_110_1 0b00101111 > +#define SHT4X_CMD_HEATER_110_01 0b00100100 > +#define SHT4X_CMD_HEATER_200_1 0b00111001 > +#define SHT4X_CMD_HEATER_200_01 0b00110010 > > #define SHT4X_CMD_LEN 1 > #define SHT4X_CRC8_LEN 1 > @@ -54,6 +61,8 @@ DECLARE_CRC8_TABLE(sht4x_crc8_table); > * @last_updated: the previous time that the SHT4X was polled > * @temperature: the latest temperature value received from the SHT4X > * @humidity: the latest humidity value received from the SHT4X > + * @heater_power: the power at which the heater will be started > + * @heater_time: the time for which the heater will remain turned on > */ > struct sht4x_data { > struct i2c_client *client; > @@ -63,6 +72,8 @@ struct sht4x_data { > long last_updated; /* in jiffies */ > s32 temperature; > s32 humidity; > + u32 heater_power; /* in milli-watts */ > + u32 heater_time; /* in milli-seconds */ > }; > > /** > @@ -215,6 +226,117 @@ static int sht4x_hwmon_write(struct device *dev, enum hwmon_sensor_types type, > } > } > > +static ssize_t heater_enable_store(struct device *dev, > + struct device_attribute *attr, > + const char *buf, > + size_t count) > +{ > + struct sht4x_data *data = dev_get_drvdata(dev); > + bool status; > + ssize_t ret; > + u8 cmd; > + > + ret = kstrtobool(buf, &status); > + if (ret) > + return ret; > + > + if (status) { > + if (data->heater_power == 20) { > + if (data->heater_time == 100) > + cmd = SHT4X_CMD_HEATER_20_01; > + else /* data->heater_time == 1000 */ > + cmd = SHT4X_CMD_HEATER_20_1; > + } else if (data->heater_power == 110) { > + if (data->heater_time == 100) > + cmd = SHT4X_CMD_HEATER_110_01; > + else /* data->heater_time == 1000 */ > + cmd = SHT4X_CMD_HEATER_110_1; > + } else { /* data->heater_power == 200 */ > + if (data->heater_time == 100) > + cmd = SHT4X_CMD_HEATER_200_01; > + else /* data->heater_time == 1000 */ > + cmd = SHT4X_CMD_HEATER_200_1; > + } > + > + ret = i2c_master_send(data->client, &cmd, SHT4X_CMD_LEN); > + } This still accepts (and ignores) writing "0" or "false". On top of that, unless I misunderstand the chip documentation, attempts to read the humidity before the "turn on heater" command completes will result in a NACK from the chip. This is not currently handled by the driver. Also, the datasheet states that a high precision measurement is done before the heater is turned off. That measurement is currently ignored. I am not entirely sure how to handle all this, but based on the information in the datasheet I can not accept your current solution. At the very least, you'll need to make sure that an attempt to read the humidity immediately after turning on the heater does not result in an error message. Thanks, Guenter
Hello,
I've been thinking on how to approach the problem of NACKs received
from the sensor while the heater is on but I haven't found
a perfectly satisfying solution either. This is due to the fact that
the device does not provide any way to check if the heater is on/off.
1. I guess that the simplest possible approach would involve sleeping
in `heater_enable_store()`:
ssize_t heater_enable_store() {
...
mutex_lock(data->lock);
ret = i2c_master_send(data->client, &cmd, SHT4X_CMD_LEN);
msleep(...) /* for >100 or >1000 ms */
mutex_unlock(data->lock);
...
}
This way, the user would have to wait for the heating to complete in
order to read RH or temperature measurement. However, I find this
solution unacceptable since it's completely unnecessary for the user
to wait for the heating to complete.
2. A better solution could be possibly to use a wait queue in order
to defer the job of enabling the heater:
struct sht4x_data {
...
struct work_struct* heater_work; /* This would be initialized
with the handler described
below */
}
The task of sending the "heater_enable" command and sleeping would be
performed by the worker function:
static void heater_enable_handler(struct work_struct *work) {
...
mutex_lock(data->lock);
ret = i2c_master_send(data->client, &cmd, SHT4X_CMD_LEN);
msleep(...) /* for >100 or >1000 ms */
mutex_unlock(data->lock);
...
}
And that above mentioned work would be scheduled
in `heater_enable_store()`:
ssize_t heater_enable_store() {
...
schedule_work(data->heater_work);
...
}
I think that this approach with work queue is better since the user
doesn't have to wait for the heating to complete and the RH or
temperature measurements can also be retrieved without the NACK error
(even though the user still may have to wait for the heater to be
off), since the `data->lock` mutex is used to guard both measurement
reads from the sensor and the heating in `heater_enable_handler`.
I'm worried though about the situation where the user writes 1 to
"heater_enable" while it's already enabled. Since the `work_struct`
is already on the queue, the `heater_enable_store` would return an
error and I see no easy solution to this for now.
Regards,
Antoni Pokusinski
On 8/28/24 09:05, Antoni Pokusinski wrote: > Hello, > > I've been thinking on how to approach the problem of NACKs received > from the sensor while the heater is on but I haven't found > a perfectly satisfying solution either. This is due to the fact that > the device does not provide any way to check if the heater is on/off. > > 1. I guess that the simplest possible approach would involve sleeping > in `heater_enable_store()`: > > ssize_t heater_enable_store() { > ... > mutex_lock(data->lock); > ret = i2c_master_send(data->client, &cmd, SHT4X_CMD_LEN); > msleep(...) /* for >100 or >1000 ms */ > mutex_unlock(data->lock); > ... > } > > This way, the user would have to wait for the heating to complete in > order to read RH or temperature measurement. However, I find this > solution unacceptable since it's completely unnecessary for the user > to wait for the heating to complete. > > 2. A better solution could be possibly to use a wait queue in order > to defer the job of enabling the heater: > > struct sht4x_data { > ... > struct work_struct* heater_work; /* This would be initialized > with the handler described > below */ > } > > The task of sending the "heater_enable" command and sleeping would be > performed by the worker function: > > static void heater_enable_handler(struct work_struct *work) { > ... > mutex_lock(data->lock); > ret = i2c_master_send(data->client, &cmd, SHT4X_CMD_LEN); > msleep(...) /* for >100 or >1000 ms */ > mutex_unlock(data->lock); > ... > } > > And that above mentioned work would be scheduled > in `heater_enable_store()`: > > ssize_t heater_enable_store() { > ... > schedule_work(data->heater_work); > ... > } > > I think that this approach with work queue is better since the user > doesn't have to wait for the heating to complete and the RH or > temperature measurements can also be retrieved without the NACK error > (even though the user still may have to wait for the heater to be > off), since the `data->lock` mutex is used to guard both measurement > reads from the sensor and the heating in `heater_enable_handler`. > > I'm worried though about the situation where the user writes 1 to > "heater_enable" while it's already enabled. Since the `work_struct` > is already on the queue, the `heater_enable_store` would return an > error and I see no easy solution to this for now. > Introducing a worker seems to be overly complicated to me. You could store the time when heating is expected to be complete, and use that time in the read function to determine if it needs to wait and/or if it should trigger another RH read request instead of just reading the RH measurement from the heater command. Something like if (still heating) wait for heater to be turned off and measurement completion if (heater was active within [select period of time]) read RH directly without additional request clear heater status else if RH was requested recently report previous RH else request RH measurement read RH This would also help with the heater_enable problem: It would just do nothing if the heater is still enabled from the previous command (or maybe return -EBUSY). If there is some additional requirement by the chip, such as that the heater must not be enabled for more than X% of the time, that information could also be used to determine if it can be enabled again. Thanks, Guenter
diff --git a/Documentation/hwmon/sht4x.rst b/Documentation/hwmon/sht4x.rst index daf21e763425..0b17f89fa1ab 100644 --- a/Documentation/hwmon/sht4x.rst +++ b/Documentation/hwmon/sht4x.rst @@ -42,4 +42,14 @@ humidity1_input Measured humidity in %H update_interval The minimum interval for polling the sensor, in milliseconds. Writable. Must be at least 2000. +heater_power The requested heater power, in milliwatts. + Available values: 20, 110, 200 (default: 200). +heater_time The requested operating time of the heater, + in milliseconds. + Available values: 100, 1000 (default 1000). +heater_enable Enable the heater with the selected power + and for the selected time in order to remove + condensed water from the sensor surface. Write-only. + + - 1: turn on =============== ============================================ diff --git a/drivers/hwmon/sht4x.c b/drivers/hwmon/sht4x.c index b8916d2735b5..20b50f7feac0 100644 --- a/drivers/hwmon/sht4x.c +++ b/drivers/hwmon/sht4x.c @@ -11,6 +11,7 @@ #include <linux/crc8.h> #include <linux/delay.h> #include <linux/hwmon.h> +#include <linux/hwmon-sysfs.h> #include <linux/i2c.h> #include <linux/jiffies.h> #include <linux/module.h> @@ -31,6 +32,12 @@ */ #define SHT4X_CMD_MEASURE_HPM 0b11111101 #define SHT4X_CMD_RESET 0b10010100 +#define SHT4X_CMD_HEATER_20_1 0b00011110 +#define SHT4X_CMD_HEATER_20_01 0b00010101 +#define SHT4X_CMD_HEATER_110_1 0b00101111 +#define SHT4X_CMD_HEATER_110_01 0b00100100 +#define SHT4X_CMD_HEATER_200_1 0b00111001 +#define SHT4X_CMD_HEATER_200_01 0b00110010 #define SHT4X_CMD_LEN 1 #define SHT4X_CRC8_LEN 1 @@ -54,6 +61,8 @@ DECLARE_CRC8_TABLE(sht4x_crc8_table); * @last_updated: the previous time that the SHT4X was polled * @temperature: the latest temperature value received from the SHT4X * @humidity: the latest humidity value received from the SHT4X + * @heater_power: the power at which the heater will be started + * @heater_time: the time for which the heater will remain turned on */ struct sht4x_data { struct i2c_client *client; @@ -63,6 +72,8 @@ struct sht4x_data { long last_updated; /* in jiffies */ s32 temperature; s32 humidity; + u32 heater_power; /* in milli-watts */ + u32 heater_time; /* in milli-seconds */ }; /** @@ -215,6 +226,117 @@ static int sht4x_hwmon_write(struct device *dev, enum hwmon_sensor_types type, } } +static ssize_t heater_enable_store(struct device *dev, + struct device_attribute *attr, + const char *buf, + size_t count) +{ + struct sht4x_data *data = dev_get_drvdata(dev); + bool status; + ssize_t ret; + u8 cmd; + + ret = kstrtobool(buf, &status); + if (ret) + return ret; + + if (status) { + if (data->heater_power == 20) { + if (data->heater_time == 100) + cmd = SHT4X_CMD_HEATER_20_01; + else /* data->heater_time == 1000 */ + cmd = SHT4X_CMD_HEATER_20_1; + } else if (data->heater_power == 110) { + if (data->heater_time == 100) + cmd = SHT4X_CMD_HEATER_110_01; + else /* data->heater_time == 1000 */ + cmd = SHT4X_CMD_HEATER_110_1; + } else { /* data->heater_power == 200 */ + if (data->heater_time == 100) + cmd = SHT4X_CMD_HEATER_200_01; + else /* data->heater_time == 1000 */ + cmd = SHT4X_CMD_HEATER_200_1; + } + + ret = i2c_master_send(data->client, &cmd, SHT4X_CMD_LEN); + } + + return ret; +} + +static ssize_t heater_power_show(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + struct sht4x_data *data = dev_get_drvdata(dev); + + return sysfs_emit(buf, "%u\n", data->heater_power); +} + +static ssize_t heater_power_store(struct device *dev, + struct device_attribute *attr, + const char *buf, + size_t count) +{ + struct sht4x_data *data = dev_get_drvdata(dev); + u32 power; + ssize_t ret; + + ret = kstrtou32(buf, 10, &power); + if (ret) + return ret; + + if (power != 20 && power != 110 && power != 200) + return -EINVAL; + + data->heater_power = power; + + return count; +} + +static ssize_t heater_time_show(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + struct sht4x_data *data = dev_get_drvdata(dev); + + return sysfs_emit(buf, "%u\n", data->heater_time); +} + +static ssize_t heater_time_store(struct device *dev, + struct device_attribute *attr, + const char *buf, + size_t count) +{ + struct sht4x_data *data = dev_get_drvdata(dev); + u32 time; + ssize_t ret; + + ret = kstrtou32(buf, 10, &time); + if (ret) + return ret; + + if (time != 100 && time != 1000) + return -EINVAL; + + data->heater_time = time; + + return count; +} + +static DEVICE_ATTR_WO(heater_enable); +static DEVICE_ATTR_RW(heater_power); +static DEVICE_ATTR_RW(heater_time); + +static struct attribute *sht4x_attrs[] = { + &dev_attr_heater_enable.attr, + &dev_attr_heater_power.attr, + &dev_attr_heater_time.attr, + NULL +}; + +ATTRIBUTE_GROUPS(sht4x); + static const struct hwmon_channel_info * const sht4x_info[] = { HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL), HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT), @@ -255,6 +377,8 @@ static int sht4x_probe(struct i2c_client *client) data->update_interval = SHT4X_MIN_POLL_INTERVAL; data->client = client; + data->heater_power = 200; + data->heater_time = 1000; mutex_init(&data->lock); @@ -270,7 +394,7 @@ static int sht4x_probe(struct i2c_client *client) client->name, data, &sht4x_chip_info, - NULL); + sht4x_groups); return PTR_ERR_OR_ZERO(hwmon_dev); }
Add support for manipulating the internal heater of sht4x devices. Enabling the heater removes condensed water from the sensor surface which disturbs the relative humidity measurements. The heater can operate at three heating levels (20, 110 or 200 milliwatts). Also, two heating durations may be selected (0.1 or 1s). Once the heating time elapses the heater is automatically switched off. Signed-off-by: Antoni Pokusinski <apokusinski01@gmail.com> --- Hello Guenter, Thanks for the review. I'm not sure if this short patch description above is now ok or shall I be even more detailed. The problem that I was facing was that when I was using the sensor for relative humidity measurements the results were always ~100% even though the correct value should be ~60%. Enabling the heater in periodic pulses to remove the condensation fixed the issue and the measurements were correct after that. Thus, I'm not sure if I should include that detailed arguments in the patch description or leave it as it is right now. Regards, Antoni Pokusinski -- Changes since v2: * heater_enable_store: remove unnecessary if * Documentation: remove incorrect info about turning off the heater * be more specific in the patch description Changes since v1: * explain the use case of the new attributes set * heater_enable attr: make it write-only * heater_enable_store: define cmd as u8 instead of u8* * heater_enable_store: remove unreachable data path * heater_enable_store: remove unnecessary lock * heater_enable_store: call i2c_master_send only if status==true * define attributes as DEVICE_ATTR_* instead of SENSOR_DEVICE_ATTR_* --- Documentation/hwmon/sht4x.rst | 10 +++ drivers/hwmon/sht4x.c | 126 +++++++++++++++++++++++++++++++++- 2 files changed, 135 insertions(+), 1 deletion(-)