Re: [PATCH 0/3] QRTR bus and Qualcomm Sensor Manager IIO drivers

[Luca Weiss]

Hi Yassine,

On Sun Apr 6, 2025 at 4:07 PM CEST, Yassine Oudjana wrote:
> Sensor Manager is a QMI service available on several Qualcomm SoCs which
> exposes available sensors and allows for getting data from them. This
> service is provided by either:
>
> - SSC (Snapdragon Sensor Core): Also known as SLPI (Sensor Low Power
>   Island). Has its own set of pins and peripherals to which sensors are
>   connected. These peripherals are generally inaccessible from the AP,
>   meaning sensors need to be operated exclusively through SSC. The only
>   known SoCs in this category are MSM8996 and MSM8998 (and their
>   derivatives).
> - ADSP (Audio DSP): Shares pins and peripherals with the AP. At least on
>   some devices, these pins could be configured as GPIOs which allows the AP
>   to access sensors by bit-banging their interfaces. Some SoCs in this
>   category are SDM630/660, MSM8953, MSM8974 and MSM8226.
>
> Before Sensor Manager becomes accessible, another service known as Sensor
> Registry needs to be provided by the AP. The remote processor that provides
> Sensor Manager will then request data from it, and once that process is
> done, will expose several services including Sensor Manager.
>
> This series adds kernel drivers for the Sensor Manager service, exposing
> sensors accessible through it as IIO devices. To facilitate probing of the
> Sensor Manager core driver, QRTR is turned into a bus, with services being
> exposed as devices. Once the Sensor Manager service becomes available, the
> kernel attaches its device to the driver added in this series. This allows
> for dynamic probing of Sensor Manager without the need for static DT
> bindings, which would also not be ideal because they would be describing
> software rather than hardware. Sensor Manager is given as a working example
> of the QRTR bus. Kernel drivers for other services may also be able
> to benefit from this change.
>
> As previously mentioned, a Sensor Registry server must run on the AP to
> provide the remote processor (either SLPI or ADSP) with necessary data.
> A userspace implementation of this server is made[1]. The server can be
> supplied with the necessary data in the form of a plain-text configuration
> file that can be pulled from the Android vendor partition (sample[2]), or
> generated from a binary file that can be pulled from the persist partition.
> A more recently developed kernel implementation of the Sensor Registry
> server[3] can also be used. This last implementation only supports reading
> data from the binary file pulled from persist. Sensor Registry remains out
> of the scope of this patch series, as the Sensor Registry server and Sensor
> Manager client (this series) are fully independent components.
>
> Due to the total lack of documentation on Sensor Manager, this driver was
> almost entirely the result of a process of capturing transactions between
> SSC and the proprietary Android daemons with several methods and manually
> decoding and interpreting them, sometimes by comparing with values acquired
> from Android APIs. A blog post[4] describes part of this process more
> detail. A little piece of downstream Android open-source code[5] was also
> used as reference during later stages of development. All of this, as well
> as a lack of time on my side for the last couple of years, meant that this
> driver had to go through a slow and intermittent development process for
> more than 3 years before reaching its current state.
>
> Currently supported sensor types include accelerometers, gyroscopes,
> magentometers, proximity and pressure sensors. Other types (namely
> light and temperature sensors) are close to being implemented.
>
> Some testing instructions may also be found here[6].

It's awesome to see this work being sent! I remember trying this quite a
while ago, so I definitely need to pick this up again and try it out!

I can try on msm8226, msm8974 and msm8953 so lots of platforms which
will gain sensor support thanks to you!

Regards
Luca

>
> [1] https://gitlab.com/msm8996-mainline/sns-reg
> [2] https://github.com/nian0114/android_vendor_xiaomi_scorpio/blob/mkn-mr1/proprietary/etc/sensors/sensor_def_qcomdev.conf
> [3] https://github.com/sdm660-mainline/linux/pull/57
> [4] https://emainline.gitlab.io/2022/04/08/Unlocking_SSC_P2.html
> [5] https://android.googlesource.com/platform/system/chre/+/android-8.0.0_r2/platform/slpi
> [6] https://gitlab.postmarketos.org/postmarketOS/pmaports/-/merge_requests/4118
>
> Yassine Oudjana (3):
>   net: qrtr: Turn QRTR into a bus
>   net: qrtr: Define macro to convert QMI version and instance to QRTR
>     instance
>   iio: Add Qualcomm Sensor Manager drivers
>
>  MAINTAINERS                                 |  18 +
>  drivers/iio/accel/Kconfig                   |  10 +
>  drivers/iio/accel/Makefile                  |   2 +
>  drivers/iio/accel/qcom_smgr_accel.c         | 138 ++++
>  drivers/iio/common/Kconfig                  |   1 +
>  drivers/iio/common/Makefile                 |   1 +
>  drivers/iio/common/qcom_smgr/Kconfig        |  16 +
>  drivers/iio/common/qcom_smgr/Makefile       |   8 +
>  drivers/iio/common/qcom_smgr/qcom_smgr.c    | 589 ++++++++++++++++
>  drivers/iio/common/qcom_smgr/qmi/Makefile   |   3 +
>  drivers/iio/common/qcom_smgr/qmi/sns_smgr.c | 711 ++++++++++++++++++++
>  drivers/iio/common/qcom_smgr/qmi/sns_smgr.h | 163 +++++
>  drivers/iio/gyro/Kconfig                    |  10 +
>  drivers/iio/gyro/Makefile                   |   2 +
>  drivers/iio/gyro/qcom_smgr_gyro.c           | 138 ++++
>  drivers/iio/magnetometer/Kconfig            |   9 +
>  drivers/iio/magnetometer/Makefile           |   2 +
>  drivers/iio/magnetometer/qcom_smgr_mag.c    | 138 ++++
>  drivers/iio/pressure/Kconfig                |  10 +
>  drivers/iio/pressure/Makefile               |   1 +
>  drivers/iio/pressure/qcom_smgr_pressure.c   | 106 +++
>  drivers/iio/proximity/Kconfig               |  10 +
>  drivers/iio/proximity/Makefile              |   1 +
>  drivers/iio/proximity/qcom_smgr_prox.c      | 106 +++
>  drivers/soc/qcom/qmi_interface.c            |   5 +-
>  include/linux/iio/common/qcom_smgr.h        |  64 ++
>  include/linux/mod_devicetable.h             |   9 +
>  include/linux/soc/qcom/qrtr.h               |  36 +
>  net/qrtr/af_qrtr.c                          |  23 +-
>  net/qrtr/qrtr.h                             |   3 +
>  net/qrtr/smd.c                              | 250 ++++++-
>  scripts/mod/devicetable-offsets.c           |   4 +
>  scripts/mod/file2alias.c                    |  10 +
>  33 files changed, 2573 insertions(+), 24 deletions(-)
>  create mode 100644 drivers/iio/accel/qcom_smgr_accel.c
>  create mode 100644 drivers/iio/common/qcom_smgr/Kconfig
>  create mode 100644 drivers/iio/common/qcom_smgr/Makefile
>  create mode 100644 drivers/iio/common/qcom_smgr/qcom_smgr.c
>  create mode 100644 drivers/iio/common/qcom_smgr/qmi/Makefile
>  create mode 100644 drivers/iio/common/qcom_smgr/qmi/sns_smgr.c
>  create mode 100644 drivers/iio/common/qcom_smgr/qmi/sns_smgr.h
>  create mode 100644 drivers/iio/gyro/qcom_smgr_gyro.c
>  create mode 100644 drivers/iio/magnetometer/qcom_smgr_mag.c
>  create mode 100644 drivers/iio/pressure/qcom_smgr_pressure.c
>  create mode 100644 drivers/iio/proximity/qcom_smgr_prox.c
>  create mode 100644 include/linux/iio/common/qcom_smgr.h
>  create mode 100644 include/linux/soc/qcom/qrtr.h