Up to now, the IIO subsystem has only supported a single scan type per channel. This scan type determines the binary format of the data in the buffer when doing buffered reads. For simple devices, there is only one scan type and all is well. But for more complex devices, there may be multiple scan types. For example, ADCs with a resolution boost feature that adds more bits to the raw sample data. Traditionally, for slow devices, we've just always used the highest resolution mode, but for high performance ADCs, this may not be always practical. Manipulating data after every read can hurt performance and in the case of hardware buffers, it may not be possible to change the format of the data in the buffer at all. There are also ADCs where enabling the higher resolution can only be done if oversampling is also enabled which may not be desireable. To allow for more flexibility, we would like to add support for multiple scan types per channel. To avoid having to touch every driver, we implemented this in a way that preserves the existing scan_type field. See the "iio: add support for multiple scan types per channel" the details. The first couple of patches are just preparation for this. [1]: https://lore.kernel.org/linux-iio/CAMknhBHOXaff__QyU-wFSNNENvs23vDX5n_ddH-Dw3s6-sQ9sg@xxxxxxxxxxxxxx/ --- Changes in v3: * Changed return type of get_current_scan_type callback to int. * Brought back updated ad7380 patches. * Link to v2: https://lore.kernel.org/r/20240524-iio-add-support-for-multiple-scan-types-v2-0-a6c328fdfab7@xxxxxxxxxxxx Changes in v2: * Use union for scan_type and scan_type_ext. * Dropped ad7380 patch - those changed will be squashed into the next revision of the series adding the driver for ad7380. * Temporary updated ad7380 patch for reference: https://github.com/dlech/linux/commit/64be3de241e73b43c5a5daa44b6b97f35f0743bf * Link to v1: https://lore.kernel.org/r/20240507-iio-add-support-for-multiple-scan-types-v1-0-95ac33ee51e9@xxxxxxxxxxxx --- David Lechner (4): iio: introduce struct iio_scan_type iio: buffer: use struct iio_scan_type to simplify code iio: add support for multiple scan types per channel iio: adc: ad7380: use spi_optimize_message() Julien Stephan (1): iio: adc: ad7380: add oversampling support drivers/iio/adc/ad7380.c | 335 +++++++++++++++++++++++++++++++------- drivers/iio/industrialio-buffer.c | 129 +++++++++++---- include/linux/iio/iio.h | 94 ++++++++--- 3 files changed, 450 insertions(+), 108 deletions(-) --- base-commit: b4bfc5f52090336f5f5b65bbdac394ac1001952d change-id: 20240507-iio-add-support-for-multiple-scan-types-f4dbcf4c2cb8
