iio: pressure: bmp280: Add triggered buffer support

BMP2xx, BME280, BMP3xx, and BMP5xx use continuous buffers for their
temperature, pressure and humidity readings. This facilitates the
use of burst/bulk reads in order to acquire data faster. The
approach is different from the one used in oneshot captures.

BMP085 & BMP1xx devices use a completely different measurement
process that is well defined and is used in their buffer_handler().
Suggested-by: Angel Iglesias <ang.iglesiasg@gmail.com>
Signed-off-by: Vasileios Amoiridis <vassilisamir@gmail.com>
Link: https://lore.kernel.org/r/20240512230524.53990-6-vassilisamir@gmail.com
Link: https://patch.msgid.link/20240628171726.124852-4-vassilisamir@gmail.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/pressure/Kconfig

@@ -31,6 +31,8 @@ config BMP280
 	select REGMAP
 	select BMP280_I2C if (I2C)
 	select BMP280_SPI if (SPI_MASTER)
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
 	help
 	  Say yes here to build support for Bosch Sensortec BMP180, BMP280, BMP380
 	  and BMP580 pressure and temperature sensors. Also supports the BME280 with

drivers/iio/pressure/bmp280-spi.c

@@ -40,14 +40,10 @@ static int bmp380_regmap_spi_read(void *context, const void *reg,
 				  size_t reg_size, void *val, size_t val_size)
 {
 	struct spi_device *spi = to_spi_device(context);
-	u8 rx_buf[4];
+	u8 rx_buf[BME280_BURST_READ_BYTES + 1];
 	ssize_t status;
 
-	/*
-	 * Maximum number of consecutive bytes read for a temperature or
-	 * pressure measurement is 3.
-	 */
-	if (val_size > 3)
+	if (val_size > BME280_BURST_READ_BYTES)
 		return -EINVAL;
 
 	/*

drivers/iio/pressure/bmp280.h

@@ -304,6 +304,16 @@
 #define BMP280_PRESS_SKIPPED		0x80000
 #define BMP280_HUMIDITY_SKIPPED		0x8000
 
+/* Number of bytes for each value */
+#define BMP280_NUM_PRESS_BYTES		3
+#define BMP280_NUM_TEMP_BYTES		3
+#define BME280_NUM_HUMIDITY_BYTES	2
+#define BMP280_BURST_READ_BYTES		(BMP280_NUM_PRESS_BYTES + \
+					 BMP280_NUM_TEMP_BYTES)
+#define BME280_BURST_READ_BYTES		(BMP280_NUM_PRESS_BYTES + \
+					 BMP280_NUM_TEMP_BYTES + \
+					 BME280_NUM_HUMIDITY_BYTES)
+
 /* Core exported structs */
 
 static const char *const bmp280_supply_names[] = {
@@ -397,13 +407,19 @@ struct bmp280_data {
 	 */
 	int sampling_freq;
 
+	/*
+	 * Data to push to userspace triggered buffer. Up to 3 channels and
+	 * s64 timestamp, aligned.
+	 */
+	s32 sensor_data[6] __aligned(8);
+
 	/*
 	 * DMA (thus cache coherency maintenance) may require the
 	 * transfer buffers to live in their own cache lines.
 	 */
 	union {
 		/* Sensor data buffer */
-		u8 buf[3];
+		u8 buf[BME280_BURST_READ_BYTES];
 		/* Calibration data buffers */
 		__le16 bmp280_cal_buf[BMP280_CONTIGUOUS_CALIB_REGS / 2];
 		__be16 bmp180_cal_buf[BMP180_REG_CALIB_COUNT / 2];
@@ -425,6 +441,7 @@ struct bmp280_chip_info {
 	const struct iio_chan_spec *channels;
 	int num_channels;
 	unsigned int start_up_time;
+	const unsigned long *avail_scan_masks;
 
 	const int *oversampling_temp_avail;
 	int num_oversampling_temp_avail;
@@ -459,6 +476,8 @@ struct bmp280_chip_info {
 	int (*read_humid)(struct bmp280_data *data, u32 *adc_humidity);
 	int (*read_calib)(struct bmp280_data *data);
 	int (*preinit)(struct bmp280_data *data);
+
+	irqreturn_t (*trigger_handler)(int irq, void *p);
 };
 
 /* Chip infos for each variant */