Add support for magnetometer Yamaha YAS537

This patchset adds YAS537 variant to the already existing driver for Yamaha YAS magnetometers.

Patch 1 is a fix on the current driver.
Patches 2-13 are cleanups and refactoring.
Patch 14 finally adds the YAS537 variant.

Changes in v6:
- Rebased to torvalds/linux master (shortly before releasing v5.20-rc1) to include Jonathan's patch "iio: magn: yas530: Use DEFINE_RUNTIME_DEV_PM_OPS() and pm_ptr() macros"
- Patch 6: In commit message corrected "This is a preparation for adding the YAS537 variant."
- Patch 6: Added period at the end of multi-line comments (3x "Used by YAS530, YAS532 and YAS533.")
- Patch 7: In commit message replaced "Additionally" by "While at it".
- Patch 9: Moved content of "product_name" and "version_names" from array directly into chip_info table due to C11 standard 6.6.7 considering array calls not as constant expression.
- Patch 9: In commit message replaced "This commit introduces" by "Introduce".
- Patch 9 & following: Introduced variable "ci" to substitute "yas5xx->chip_info".
- Patch 9: Removed introduction of "enum chip_ids" as "yas5xx->chip". Instead, in the function yas5xx_probe(), used "id->driver_data" directly to initialize enumeration of "yas5xx_chip_info_tbl[]".
- Patch 12: Moved values "t_ref" and "min_temp_x10" from array directly into chip_info table due to C11 standard 6.6.7 considering array calls not as constant expression. Comments were partially moved into the kernel doc of struct yas5xx_chip_info.
- Patch 12: In the function yas5xx_calc_temperature(), changed data type of min_temp_x10 from int to s16 (as it's declared in struct yas5xx_chip_info).
- Patch 13: In commit message corrected typo in word "function".
- Patch 14: In commit message changed "This adds support" to "Add support".
- Patch 14: In commit message changed wording "for YAS537 in the mainline".

Changes in v5:
- Rebased to torvalds/linux v5.19.
- Patch 6: Moved 3x comment "Used by YAS530, YAS532 and YAS533" into kernel doc.
- Patch 6: Corrected missing renaming of 2x "yas530_get_measure", 1x "yas530_power_on", 1x "YAS530_ACTUATE_INIT_COIL", 1x "YAS530_MEASURE".
- Patch 7: Added "Suggested-by:" tag.
- Split patch 9 v4 "Introduce 'chip_info' structure" into five patches 9-13.
- Patch 9: In commit message changed wording "Device Tree".
- Patch 9: Added commas to non-terminating arrays of "yas5xx_product_name", "yas5xx_version_name", and "yas5xx_chip_info".
- Patch 9: Added "product_name" and "version_name" to "chip_info" struct.
- Patch 9: Added "s" to array name "yas5xx_version_names".
- Patch 9: Added indices to array "yas5xx_version_names".
- Patch 9: For strings in arrays "yas5xx_product_name" and "yas5xx_version_names", applied char * instead of char [].
- Patch 9: Initialize struct "chip_info" as const.
- Patch 9: In function yas5xx_probe(), moved declaration of "id_check" to a new line.
- Patch 9: In function yas5xx_probe(), after "if (id_check != yas5xx->chip_info->devid)" applied dev_err_probe().
- Patch 10: In function yas5xx_volatile_reg(), renamed integer "j" into "reg_qty".
- Patch 12: Improved comments on arrays "t_ref_counts" and "min_temp_celsius_x10".
- Patch 12: Changed arrays "t_ref_counts" and "min_temp_celsius_x10" to static.
- Patch 12: Corrected wrong spelling of "celcius" with "c" in array "min_temp_celsius_x10"
- Patch 13: In function yas5xx_probe(), added the conditional "if (yas5xx->chip_info->measure_offsets)" as a preparatory step for YAS537.
- Patch 14: In function yas537_power_on(), replaced comment "Write registers according to Android driver" by "Writing ADCCAL and TRM registers".
- Patch 14: In function yas537_power_on(), write register ADCCAL as a bulk write.
- Patch 14: In function yas537_power_on(), in formula for "intrvl" replaced value "1000" by MILLI. Added "linux/units.h" to includes.

Changes in v4:
- Rebased to torvalds/linux v5.19-rc4, as this now includes Linus' patch "Fix memchr_inv() misuse" on driver yamaha-yas530.
- Removed redundant Cc tags.
- Patch 2: Replaced "<= ... + 7" by "< ... + 8" and adapted commit message.
- Patch 3: Added default for switch statement, I forgot to add this.
- Patch 4: In function yas5xx_get_measure(), changed wording "milli degrees" to "millidegrees".
- Patch 6: Changed the renaming of function from "yas530_532_" to "yas530_". Same for registers. Added additional comments where appropriate.
- Patch 6: Removed "Reviewed-by:" tag of Andy.
- Split patch 7 v3 into two patches -> patch 7 v4 and patch 8 v4.
- Patch 8: Applied "if (a && b)" suggestion at memchr_inv() by Andy in function yas532_get_calibration_data().
- Patch 8: Removed defines for device IDs YAS537 and YAS539 and accordingly the comment "These variant IDs are known from code dumps".
- Patch 9: New patch to introduce the "chip_info" approach.
- Patch 10: In function yas537_get_calibration_data(), removed "the exact meaning is unknown" from comment "Writing SRST register".
- Patch 10: Also applied "if (a && b)" suggestion at memchr_inv() by Andy in function yas537_get_calibration_data(). Additionally changed the second condition from "== 0" to "!".
- Patch 10: In function yas537_get_calibration_data(), removed empty lines within switch statement. In that context, removed comment "Get data into these four blocks val1 to val4".
- Patch 10: In Kconfig, simplified wording.
- Patch 10: In function yas537_get_calibration_data() "case YAS537_VERSION_0", reduced indent of "for" loop by splitting it into multiple loops. I didn't use integer j, as it was suggested by Jonathan, because only using integer i is more consistant with the loop in "case YAS537_VERSION_1".
- Accordingly, split the "for" loop in "case YAS537_VERSION_1" into two loops as well. Technically this isn't neccessary but it improves readability.
- Patch 10: Added new defines of masks for YAS537 and applied these by FIELD_PREP and FIELD_GET in function yas537_get_calibration_data() within "case YAS537_VERSION_1".
- Patch 10: In function yas537_power_on(), added spaced at "YAS537_ADCCAL + 1".

Changes in v3:
- In patch 3 fixed 2x typo "Divide".
- In commit message of patch 4 fixed wording "in the yas5xx_get_measure() function".
- In patch 4 in the comment for the temperature calculation fixed wording "is the number of counts".
- In patch 4 added defaults to switch statements.
- Splitted stray changes into new patch 7 v3. "Add YAS537 variant" is now patch 8 v3. I haven't added "Reviewed-by:" tag of Linus to patch 7 v3 because as a separate patch these changes appear in a different context.
- In new patch 7 v3, changed printk format specifiers in the function yas530_get_calibration_data() to "%16ph" and in the function yas532_get_calibration_data() to "%14ph". The first one is also a minor correction in behaviour, as the calibration data array size of YAS530 is 16 (the dev_dbg printed 14 before).
- Rebased to linux-next to include patch bb52d3691db8 "iio: magnetometer:
yas530: Fix memchr_inv() misuse".
- In patch 7 v3, changed memchr_inv() line for YAS532.
- In patch 8 v3 in the function yas537_get_calibration_data(), changed memchr_inv() line for YAS537.
- Removed comment "corresponds to 0x70" at define YAS537_MAG_AVERAGE_32_MASK.
- Added suffixes _US and _MS in defines for YAS537.
- In the function yas537_measure(), removed comments "Read data", "Arrange data", "Assign data".
- In the function yas537_measure(), replaced bitwise shift by get_unaligned_be16().
- Replaced "if (h[i] < -8192)" etc. by clamp_val().
- In the functions yas537_measure() and yas537_get_measure(), replaced 8192 by BIT(13) and 16384 by BIT(14).
- Fixed typo "resolution" in the function yas5xx_read_raw().
- Fixed typo "Divide" in patch 8 v3 in the function yas5xx_read_raw().
- In patch 8 v3 in the yas537_get_calibration_data(), changed printk format specifier to "%17ph"
- In the functions yas537_measure() and yas537_get_calibration_data(), drop some parentheses in regmap_write().
- In the function yas537_power_on(), added comment "Wait until the coil has ramped up".
- In the function yas5xx_probe(), put YAS537 variant and version printings into one print.
- In the function yas537_get_measure(), fixed wording "is the number of counts" in the comment for the temperature calculation.
- In the function yas537_get_measure(), added product description document No. into the comment for the temperature calculation (as I first thought the review comment "the number" is related to this).
- In the function yas537_get_calibration_data(), corrected comment "Get data into these four blocks val1 to val4".

Changes in v2:
- Reordered the patchset by moving patch 4 v1 to patch 1 v2.
- Removed patch 6 v1 ("Remove redundant defaults on switch devid")
- Accordingly, added "default:" to each switch statement in patch 7.
- Moved renamings in patch 7 v1 into a separate new patch 6 v2. I added the "Reviewed-by:" tag of Linus to both patches, hope that's ok, else feel free to comment.
- Removed regmap reads and related debug dumps in patch 7 in function yas537_dump_calibration(). As this function now applies to version 1 only, replaced switch statement by if clause.
- Also removed "hard_offsets" debug dumps in that function.
- Fixed typo "initialized" in commit message of patch 7.

v5: https://lore.kernel.org/linux-iio/[email protected]/T/#t
v4: https://lore.kernel.org/linux-iio/[email protected]/T/#t
v3: https://lore.kernel.org/linux-iio/[email protected]/T/#t
v2: https://lore.kernel.org/linux-iio/[email protected]/T/#t
v1: https://lore.kernel.org/linux-iio/[email protected]/T/#t

Jakob Hauser (14):
iio: magnetometer: yas530: Change data type of hard_offsets to signed
iio: magnetometer: yas530: Change range of data in volatile register
iio: magnetometer: yas530: Correct scaling of magnetic axes
iio: magnetometer: yas530: Correct temperature handling
iio: magnetometer: yas530: Change data type of calibration
coefficients
iio: magnetometer: yas530: Rename functions and registers
iio: magnetometer: yas530: Move printk %*ph parameters out from stack
iio: magnetometer: yas530: Apply documentation and style fixes
iio: magnetometer: yas530: Introduce "chip_info" structure
iio: magnetometer: yas530: Add volatile registers to "chip_info"
iio: magnetometer: yas530: Add IIO scaling to "chip_info"
iio: magnetometer: yas530: Add temperature calculation to "chip_info"
iio: magnetometer: yas530: Add function pointers to "chip_info"
iio: magnetometer: yas530: Add YAS537 variant

 drivers/iio/magnetometer/Kconfig         |   4 +-
 drivers/iio/magnetometer/yamaha-yas530.c | 830 +++++++++++++++++++----
 2 files changed, 703 insertions(+), 131 deletions(-)

2.35.1