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Sat, 31 Oct 2026 22:40:31 -0700 (PDT) Received: from localhost.localdomain ([101.0.63.213]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-36a42935b4asm32378828eec.16.2026.10.31.22.40.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 31 Oct 2026 22:40:30 -0700 (PDT) From: Nikhil Gautam To: linux-iio@vger.kernel.org Cc: linux-kernel@vger.kernel.org, jic23@kernel.org, dlechner@baylibre.com, nuno.sa@analog.com, andy@kernel.org, Nikhil Gautam Subject: [PATCH v4] iio: chemical: ccs811: Make sampling frequency configurable Date: Sun, 1 Nov 2026 11:10:19 +0530 Message-Id: <20261101054019.10188-1-nikhilgtr@gmail.com> X-Mailer: git-send-email 2.39.5 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Allow userspace to configure the CCS811 IAQ measurement rate through the IIO sampling_frequency attribute. Support the three IAQ measurement modes with sampling frequencies of 1 Hz, 0.1 Hz, and approximately 0.016667 Hz, corresponding to measurement intervals of 1, 10, and 60 seconds. Preserve unrelated bits in the MEAS_MODE register when updating the drive mode, and cache the selected mode after a successful register write. Expose the supported frequencies through sampling_frequency_available. Signed-off-by: Nikhil Gautam --- Changes in v4: - Move the changelog below the cutter line. - Use a two-dimensional sampling frequency table with a matching drive mode table, and look entries up with simple loops. - Use IIO_DEV_ACQUIRE_DIRECT_MODE() in write_raw(). Changes in v3: - Reuse the sampling frequency array instead of duplicating frequency values. - Separate register updates from locking and wakeup handling. - Use a separate variable for the updated MEAS_MODE register value. - Simplify the sampling frequency getter. - Mark the completed drive-mode configuration TODO as done. Changes in v2: - Fix the Clang build error caused by guard() in the switch statement. drivers/iio/chemical/ccs811.c | 154 ++++++++++++++++++++++++++++++++-- 1 file changed, 148 insertions(+), 6 deletions(-) diff --git a/drivers/iio/chemical/ccs811.c b/drivers/iio/chemical/ccs811.c index d126ee12ffe5..1a865377361c 100644 --- a/drivers/iio/chemical/ccs811.c +++ b/drivers/iio/chemical/ccs811.c @@ -9,7 +9,7 @@ * IIO driver for AMS CCS811 (I2C address 0x5A/0x5B set by ADDR Low/High) * * TODO: - * 1. Make the drive mode selectable form userspace + * 1. DONE. Was: "Make the drive mode selectable form userspace" * 2. Add support for interrupts * 3. Adjust time to wait for data to be ready based on selected operation mode * 4. Read error register and put the information in logs @@ -54,6 +54,7 @@ #define CCS811_STATUS_FW_MODE_APPLICATION BIT(7) /* Measurement modes */ +#define CCS811_MODE_MASK GENMASK(6, 4) #define CCS811_MODE_IDLE 0x00 #define CCS811_MODE_IAQ_1SEC 0x10 #define CCS811_MODE_IAQ_10SEC 0x20 @@ -64,6 +65,19 @@ #define CCS811_VOLTAGE_MASK 0x3FF +static const int ccs811_samp_freq[][2] = { + { 1, 0 }, + { 0, 100000 }, + { 0, 16667 }, +}; + +/* Drive mode for each entry of ccs811_samp_freq[], same order */ +static const u8 ccs811_drive_mode[] = { + CCS811_MODE_IAQ_1SEC, + CCS811_MODE_IAQ_10SEC, + CCS811_MODE_IAQ_60SEC, +}; + struct ccs811_reading { __be16 co2; __be16 voc; @@ -79,6 +93,7 @@ struct ccs811_data { struct iio_trigger *drdy_trig; struct gpio_desc *wakeup_gpio; bool drdy_trig_on; + u8 drive_mode; /* Ensures correct alignment of timestamp if present */ struct { s16 channels[2]; @@ -103,6 +118,8 @@ static const struct iio_chan_spec ccs811_channels[] = { .modified = 1, .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE), + .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SAMP_FREQ), + .info_mask_shared_by_type_available = BIT(IIO_CHAN_INFO_SAMP_FREQ), .scan_index = 0, .scan_type = { .sign = 'u', @@ -163,16 +180,21 @@ static int ccs811_start_sensor_application(struct i2c_client *client) return 0; } -static int ccs811_setup(struct i2c_client *client) +static int ccs811_setup(struct ccs811_data *data) { int ret; - ret = ccs811_start_sensor_application(client); + ret = ccs811_start_sensor_application(data->client); + if (ret < 0) + return ret; + + ret = i2c_smbus_write_byte_data(data->client, CCS811_MEAS_MODE, + CCS811_MODE_IAQ_1SEC); if (ret < 0) return ret; - return i2c_smbus_write_byte_data(client, CCS811_MEAS_MODE, - CCS811_MODE_IAQ_1SEC); + data->drive_mode = CCS811_MODE_IAQ_1SEC; + return 0; } static void ccs811_set_wakeup(struct ccs811_data *data, bool enable) @@ -188,6 +210,54 @@ static void ccs811_set_wakeup(struct ccs811_data *data, bool enable) usleep_range(20, 30); } +static int ccs811_update_sampling_freq(struct ccs811_data *data, + int val, int val2) +{ + u8 drive_mode; + u8 mode; + int i, ret; + + for (i = 0; i < ARRAY_SIZE(ccs811_samp_freq); i++) { + if (val == ccs811_samp_freq[i][0] && + val2 == ccs811_samp_freq[i][1]) + break; + } + + if (i == ARRAY_SIZE(ccs811_samp_freq)) + return -EINVAL; + + drive_mode = ccs811_drive_mode[i]; + + ret = i2c_smbus_read_byte_data(data->client, CCS811_MEAS_MODE); + if (ret < 0) + return ret; + + mode = (ret & ~CCS811_MODE_MASK) | drive_mode; + + ret = i2c_smbus_write_byte_data(data->client, CCS811_MEAS_MODE, + mode); + if (ret < 0) + return ret; + + data->drive_mode = drive_mode; + + return 0; +} + +static int ccs811_set_sampling_freq(struct ccs811_data *data, + int val, int val2) +{ + int ret; + + guard(mutex)(&data->lock); + + ccs811_set_wakeup(data, true); + ret = ccs811_update_sampling_freq(data, val, val2); + ccs811_set_wakeup(data, false); + + return ret; +} + static int ccs811_get_measurement(struct ccs811_data *data) { int ret, tries = 11; @@ -215,6 +285,26 @@ static int ccs811_get_measurement(struct ccs811_data *data) return ret; } +static int ccs811_get_sampling_freq(struct ccs811_data *data, + int *val, int *val2) +{ + int i; + + guard(mutex)(&data->lock); + + for (i = 0; i < ARRAY_SIZE(ccs811_drive_mode); i++) { + if (ccs811_drive_mode[i] != data->drive_mode) + continue; + + *val = ccs811_samp_freq[i][0]; + *val2 = ccs811_samp_freq[i][1]; + + return IIO_VAL_INT_PLUS_MICRO; + } + + return -EINVAL; +} + static int ccs811_read_info_raw(struct ccs811_data *data, struct iio_chan_spec const *chan, int *val, int mask) @@ -249,6 +339,28 @@ static int ccs811_read_info_raw(struct ccs811_data *data, } } +static int ccs811_write_raw(struct iio_dev *indio_dev, + struct iio_chan_spec const *chan, + int val, int val2, long mask) +{ + struct ccs811_data *data = iio_priv(indio_dev); + int ret; + + switch (mask) { + case IIO_CHAN_INFO_SAMP_FREQ: + IIO_DEV_ACQUIRE_DIRECT_MODE(indio_dev, claim); + if (IIO_DEV_ACQUIRE_FAILED(claim)) + return -EBUSY; + + ret = ccs811_set_sampling_freq(data, val, val2); + + return ret; + + default: + return -EINVAL; + } +} + static int ccs811_read_raw(struct iio_dev *indio_dev, struct iio_chan_spec const *chan, int *val, int *val2, long mask) @@ -293,13 +405,43 @@ static int ccs811_read_raw(struct iio_dev *indio_dev, default: return -EINVAL; } + case IIO_CHAN_INFO_SAMP_FREQ: + return ccs811_get_sampling_freq(data, val, val2); default: return -EINVAL; } } +static int ccs811_read_avail(struct iio_dev *indio_dev, + struct iio_chan_spec const *chan, + const int **vals, int *type, int *length, + long mask) +{ + if (mask != IIO_CHAN_INFO_SAMP_FREQ) + return -EINVAL; + + *vals = (const int *)ccs811_samp_freq; + *type = IIO_VAL_INT_PLUS_MICRO; + *length = ARRAY_SIZE(ccs811_samp_freq) * 2; + + return IIO_AVAIL_LIST; +} + +static int ccs811_write_raw_get_fmt(struct iio_dev *indio_dev, + struct iio_chan_spec const *chan, + long mask) +{ + if (mask == IIO_CHAN_INFO_SAMP_FREQ) + return IIO_VAL_INT_PLUS_MICRO; + + return -EINVAL; +} + static const struct iio_info ccs811_info = { .read_raw = ccs811_read_raw, + .write_raw = ccs811_write_raw, + .read_avail = ccs811_read_avail, + .write_raw_get_fmt = ccs811_write_raw_get_fmt, }; static int ccs811_set_trigger_state(struct iio_trigger *trig, @@ -460,7 +602,7 @@ static int ccs811_probe(struct i2c_client *client) return -ENODEV; } - ret = ccs811_setup(client); + ret = ccs811_setup(data); if (ret < 0) { ccs811_set_wakeup(data, false); return ret; -- 2.39.5