Hello, N.B.: the following text is mostly a repeat of cover letter from the previous RFC for the uninitiated, which can be found at https://lore.kernel.org/linux-serial/20200923151511.3842150-1-luzmaximilian@xxxxxxxxx/ See "Changes" below for an overview of differences between the RFC and this patchset. I hope I have addressed all comments from that in this version, thank you again for those. The Surface System Aggregator Module (we'll refer to it as Surface Aggregator or SAM below) is an embedded controller (EC) found on various Microsoft Surface devices. Specifically, all 4th and later generation Surface devices, i.e. Surface Pro 4, Surface Book 1 and later, with the exception of the Surface Go series and the Surface Duo. Notably, it seems like this EC can also be found on the ARM-based Surface Pro X [1]. Functionality provided by this EC depends on the Surface model and can (roughly) be broken down by their generations: Starting with 5th generation devices (Surface Pro 2017/5, Surface Book 2, Surface Laptop 1, and later), the EC provides battery and thermal readings, as well as access to the real-time clock. On 5th and 6th generations, these features, specifically, are provided via the ACPI interface of the EC, referred to as Surface ACPI Notify (SAN), i.e. they act as standard ACPI devices of that type, but require a driver translating requests written to an ACPI operation region to requests to the EC. On 7th generation devices, the ACPI interface is (largely) gone, and has been replaced with custom battery and thermal drivers, directly querying the EC. Additionally, HID keyboard and touchpad input for Surface models with these devices built in can be handled via the EC: On the Surface Laptops 1 and 2, this includes only the keyboard, while on the Surface Laptop 3 and Book 3, this includes both touchpad and keyboard. In this case, actual input is provided as HID data and the EC connection acts as HID transport, thus requiring a special transport driver for those devices to work. Further, all known devices (5th and later generations) also support changing of performance/cooling modes, which can influence cooling capabilities of the device (e.g. prefer silent operation over performance), and may influence power limits (e.g. of the discrete GPU found on Surface Books). While this constitutes all major functionality, some more device specific functionality is also handled by the EC. For example, on the Surface Books, the EC handles detaching of the clipboard (i.e. the upper part with screen and CPU) from the base (the lower part with keyboard and optional discrete GPU) and can influence its behavior (i.e. it provides an interface via which detachment can be requested, aborted, or confirmed). It can also be used to detect if there has been a base attached to the clipboard, and if so what type. This patch-series adds the basis for supporting this EC and the features provided by it, by, first, implementing a communication driver providing a fundamental API for client drivers, handling specific aspects of the EC. Additionally, it builds on top of that to provide a dedicated bus and device type to better manage EC clients (and break it down pseudo- device-wise), especially in the case when these client devices are not described in ACPI, i.e. cannot be discovered by conventional means. Furthermore, it provides support for debugging and prototyping via an optional user-space interface, and, lastly, also support for the aforementioned ACPI interface, allowing ACPI to communicate with the EC directly. This series only addresses 5th and later generation Surface models as the communication interface has changed substantially from 4th to 5th generation, and the 4th generation interface has not been reverse- engineered yet. Specifically, the underlying transport has been changed from HID feature and input-/output-reports to serial communication via an UART and a custom protocol. Support for 4th generation devices may be added in the future, but as currently not much is known about 4th generation SAM, it yet remains to be seen if this can happen as addition to this subsystem, or if it will be easier to implement this as separate platform driver. Especially as the 4th generation EC does not seem to provide much of the functionality found on 5th and later generations (e.g. no battery status reporting, no thermal reporting, ..., we assume it's just clipboard detachment on the Surface Book 1 and performance mode setting). In more detail, this series adds a driver for the Surface Serial Hub (SSH), the 5th- and later-generation communication channel to the EC, a pseudo-device and driver exposing a misc-device that can be used to communicate with the EC from user-space, intended for debugging, testing, and prototyping, as well as a driver for the Surface ACPI Notify (SAN) device, i.e. the interface between ACPI and EC. Some more details on those can be found on the individual commit messages. This series, apart from the SAN and user-space drivers, does not add any client drivers. This will be handled via future patches once the core has been accepted (and the other client drivers have been cleaned up a bit). On the top level, EC communication via the SSH driver can be broken down into requests (sent from host to EC), corresponding responses (sent from EC to host, associated with and triggered by a request), and events (sent from EC to host without association to a request). The SSH driver manages all communication (i.e. matches responses to requests, enables and disables events, and manages event handlers/notifiers installed by client drivers). On the lower levels, SSH communication is packet-based, and described in more detail in the documentation added in this series (specifically ssh.rst). This set of modules and drivers has been developed out of tree at [2] and used/tested in the kernel we provide at [3] pretty much since its beginnings. It has been developed by reverse-engineering the SSH protocol, mostly through the ACPI interface, communication dumps obtained from listening in on Windows, and deduction. So things may be wrong. There have been some attempts at reverse-engineering existing drivers, which also gave a bit of insight for development, however, I haven't gotten very far on that front beyond some more higher-level concepts and detecting a couple of new EC commands/confirming the functionality of already known commands. Driver and module names have been chosen to align with Windows driver names, some field, variable, and concept names have been chosen to align with ACPI code (or at least with what I think some of the more cryptic names could mean and make sense in the respective context, e.g. IID -> Instance ID, TC -> Target Category). This patch-set can also be found at the following repository and reference, if you prefer to look at a kernel tree instead of these emails: https://github.com/linux-surface/kernel tags/s/surface-aggregator/v1 Thanks, Max [1]: The Surface Pro X is, however, currently considered unsupported due to a lack of test candidates and, as it seems, general lack of Linux support on other parts. AFAIK there is an issue preventing serial devices from being registered, on which the core driver in this series is build on, thus there is no way to even test that at this point. I'd be happy to work out any issues regarding SAM on the Pro X at some point in the future, provided someone can/wants to actually test it. [2]: https://github.com/linux-surface/surface-aggregator-module [3]: https://github.com/linux-surface/linux-surface Note: This patch depends on [PATCH v4] platform/surface: Create a platform subdirectory for Microsoft Surface devices which can be found at https://lore.kernel.org/platform-driver-x86/20201009141128.683254-1-luzmaximilian@xxxxxxxxx/ and is currently in platform-drivers-x86/for-next. Changes from the previous RFC (overview): - move to platform/surface - add copyright lines - change SPDX identifier to GPL-2.0+ (was GPL-2.0-or-later) - change user-space interface from debugfs to misc-device - address issues in user-space interface - fix typos in commit messages and documentation - fix some bugs, address other issues Changes regarding specific patches (and more details) can be found on the individual patch. Maximilian Luz (9): platform/surface: Add Surface Aggregator subsystem platform/surface: aggregator: Add control packet allocation caching platform/surface: aggregator: Add event item allocation caching platform/surface: aggregator: Add trace points platform/surface: aggregator: Add error injection capabilities platform/surface: aggregator: Add dedicated bus and device type docs: driver-api: Add Surface Aggregator subsystem documentation platform/surface: Add Surface Aggregator user-space interface platform/surface: Add Surface ACPI Notify driver Documentation/driver-api/index.rst | 1 + .../surface_aggregator/client-api.rst | 38 + .../driver-api/surface_aggregator/client.rst | 394 +++ .../surface_aggregator/clients/cdev.rst | 85 + .../surface_aggregator/clients/index.rst | 21 + .../surface_aggregator/clients/san.rst | 44 + .../driver-api/surface_aggregator/index.rst | 21 + .../surface_aggregator/internal-api.rst | 67 + .../surface_aggregator/internal.rst | 50 + .../surface_aggregator/overview.rst | 76 + .../driver-api/surface_aggregator/ssh.rst | 343 +++ MAINTAINERS | 13 + drivers/platform/surface/Kconfig | 39 + drivers/platform/surface/Makefile | 3 + drivers/platform/surface/aggregator/Kconfig | 65 + drivers/platform/surface/aggregator/Makefile | 17 + drivers/platform/surface/aggregator/bus.c | 424 +++ drivers/platform/surface/aggregator/bus.h | 27 + .../platform/surface/aggregator/controller.c | 2557 +++++++++++++++++ .../platform/surface/aggregator/controller.h | 288 ++ drivers/platform/surface/aggregator/core.c | 831 ++++++ .../platform/surface/aggregator/ssh_msgb.h | 201 ++ .../surface/aggregator/ssh_packet_layer.c | 2009 +++++++++++++ .../surface/aggregator/ssh_packet_layer.h | 175 ++ .../platform/surface/aggregator/ssh_parser.c | 229 ++ .../platform/surface/aggregator/ssh_parser.h | 157 + .../surface/aggregator/ssh_request_layer.c | 1254 ++++++++ .../surface/aggregator/ssh_request_layer.h | 142 + drivers/platform/surface/aggregator/trace.h | 625 ++++ .../platform/surface/surface_acpi_notify.c | 884 ++++++ .../surface/surface_aggregator_cdev.c | 299 ++ include/linux/mod_devicetable.h | 18 + include/linux/surface_acpi_notify.h | 39 + include/linux/surface_aggregator/controller.h | 832 ++++++ include/linux/surface_aggregator/device.h | 430 +++ include/linux/surface_aggregator/serial_hub.h | 659 +++++ include/uapi/linux/surface_aggregator/cdev.h | 58 + scripts/mod/devicetable-offsets.c | 8 + scripts/mod/file2alias.c | 23 + 39 files changed, 13446 insertions(+) create mode 100644 Documentation/driver-api/surface_aggregator/client-api.rst create mode 100644 Documentation/driver-api/surface_aggregator/client.rst create mode 100644 Documentation/driver-api/surface_aggregator/clients/cdev.rst create mode 100644 Documentation/driver-api/surface_aggregator/clients/index.rst create mode 100644 Documentation/driver-api/surface_aggregator/clients/san.rst create mode 100644 Documentation/driver-api/surface_aggregator/index.rst create mode 100644 Documentation/driver-api/surface_aggregator/internal-api.rst create mode 100644 Documentation/driver-api/surface_aggregator/internal.rst create mode 100644 Documentation/driver-api/surface_aggregator/overview.rst create mode 100644 Documentation/driver-api/surface_aggregator/ssh.rst create mode 100644 drivers/platform/surface/aggregator/Kconfig create mode 100644 drivers/platform/surface/aggregator/Makefile create mode 100644 drivers/platform/surface/aggregator/bus.c create mode 100644 drivers/platform/surface/aggregator/bus.h create mode 100644 drivers/platform/surface/aggregator/controller.c create mode 100644 drivers/platform/surface/aggregator/controller.h create mode 100644 drivers/platform/surface/aggregator/core.c create mode 100644 drivers/platform/surface/aggregator/ssh_msgb.h create mode 100644 drivers/platform/surface/aggregator/ssh_packet_layer.c create mode 100644 drivers/platform/surface/aggregator/ssh_packet_layer.h create mode 100644 drivers/platform/surface/aggregator/ssh_parser.c create mode 100644 drivers/platform/surface/aggregator/ssh_parser.h create mode 100644 drivers/platform/surface/aggregator/ssh_request_layer.c create mode 100644 drivers/platform/surface/aggregator/ssh_request_layer.h create mode 100644 drivers/platform/surface/aggregator/trace.h create mode 100644 drivers/platform/surface/surface_acpi_notify.c create mode 100644 drivers/platform/surface/surface_aggregator_cdev.c create mode 100644 include/linux/surface_acpi_notify.h create mode 100644 include/linux/surface_aggregator/controller.h create mode 100644 include/linux/surface_aggregator/device.h create mode 100644 include/linux/surface_aggregator/serial_hub.h create mode 100644 include/uapi/linux/surface_aggregator/cdev.h -- 2.29.2
