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Add a driver providing a tablet-mode switch input device for Microsoft Surface devices using the Surface Aggregator KIP subsystem (to manage detachable peripherals) or POS subsystem (to obtain device posture information). The KIP (full name unknown, abbreviation found through reverse engineering) subsystem is used on the Surface Pro 8 and Surface Pro X to manage the keyboard cover. Among other things, it provides information on the positioning (posture) of the cover (closed, laptop-style, detached, folded-back, ...), which can be used to implement an input device providing the SW_TABLET_MODE event. Similarly, the POS (posture information) subsystem provides such information on the Surface Laptop Studio, with the difference being that the keyboard is not detachable. As implementing the tablet-mode switch for both subsystems is largely similar, the driver proposed in this commit, in large, acts as a generic tablet mode switch driver framework for the Surface Aggregator Module. Specific implementations using this framework are provided for the KIP and POS subsystems, adding tablet-mode switch support to the aforementioned devices. A few more notes on the Surface Laptop Studio: A peculiarity of the Surface Laptop Studio is its "slate/tent" mode (symbolized: user> _/\). In this mode, the screen covers the keyboard but leaves the touchpad exposed. This is essentially a mode in-between tablet and laptop, and it is debatable whether tablet-mode should be enabled in this mode. We therefore let the user decide this via a module parameter. In particular, tablet-mode may bring up the on-screen touch keyboard more easily, which would be desirable in this mode. However, some user-space software currently also decides to disable keyboard and, more importantly, touchpad input, while the touchpad is still accessible in the "slate/tent" mode. Furthermore, this mode shares its identifier with "slate/flipped" mode where the screen is flipped 180° and the keyboard points away from the user (symbolized: user> /_). In this mode we would like to enable auto-rotation, something that user-space software may only do when tablet-mode is enabled. We therefore default to the slate-mode enabling the tablet-mode switch. Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com> Link: https://lore.kernel.org/r/20220624183642.910893-3-luzmaximilian@gmail.com Reviewed-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Hans de Goede <hdegoede@redhat.com> |
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This directory attempts to document the ABI between the Linux kernel and userspace, and the relative stability of these interfaces. Due to the everchanging nature of Linux, and the differing maturity levels, these interfaces should be used by userspace programs in different ways. We have four different levels of ABI stability, as shown by the four different subdirectories in this location. Interfaces may change levels of stability according to the rules described below. The different levels of stability are: stable/ This directory documents the interfaces that the developer has defined to be stable. Userspace programs are free to use these interfaces with no restrictions, and backward compatibility for them will be guaranteed for at least 2 years. Most interfaces (like syscalls) are expected to never change and always be available. testing/ This directory documents interfaces that are felt to be stable, as the main development of this interface has been completed. The interface can be changed to add new features, but the current interface will not break by doing this, unless grave errors or security problems are found in them. Userspace programs can start to rely on these interfaces, but they must be aware of changes that can occur before these interfaces move to be marked stable. Programs that use these interfaces are strongly encouraged to add their name to the description of these interfaces, so that the kernel developers can easily notify them if any changes occur (see the description of the layout of the files below for details on how to do this.) obsolete/ This directory documents interfaces that are still remaining in the kernel, but are marked to be removed at some later point in time. The description of the interface will document the reason why it is obsolete and when it can be expected to be removed. removed/ This directory contains a list of the old interfaces that have been removed from the kernel. Every file in these directories will contain the following information: What: Short description of the interface Date: Date created KernelVersion: Kernel version this feature first showed up in. Contact: Primary contact for this interface (may be a mailing list) Description: Long description of the interface and how to use it. Users: All users of this interface who wish to be notified when it changes. This is very important for interfaces in the "testing" stage, so that kernel developers can work with userspace developers to ensure that things do not break in ways that are unacceptable. It is also important to get feedback for these interfaces to make sure they are working in a proper way and do not need to be changed further. Note: The fields should be use a simple notation, compatible with ReST markup. Also, the file **should not** have a top-level index, like:: === foo === How things move between levels: Interfaces in stable may move to obsolete, as long as the proper notification is given. Interfaces may be removed from obsolete and the kernel as long as the documented amount of time has gone by. Interfaces in the testing state can move to the stable state when the developers feel they are finished. They cannot be removed from the kernel tree without going through the obsolete state first. It's up to the developer to place their interfaces in the category they wish for it to start out in. Notable bits of non-ABI, which should not under any circumstances be considered stable: - Kconfig. Userspace should not rely on the presence or absence of any particular Kconfig symbol, in /proc/config.gz, in the copy of .config commonly installed to /boot, or in any invocation of the kernel build process. - Kernel-internal symbols. Do not rely on the presence, absence, location, or type of any kernel symbol, either in System.map files or the kernel binary itself. See Documentation/process/stable-api-nonsense.rst.