treewide, serdev: change receive_buf() return type to size_t

receive_buf() is called from ttyport_receive_buf() that expects values
">= 0" from serdev_controller_receive_buf(), change its return type from
ssize_t to size_t.

The need for this clean-up was noticed while fixing a warning, see
commit 94d053942544 ("Bluetooth: btnxpuart: fix recv_buf() return value").
Changing the callback prototype to return an unsigned seems the best way
to document the API and ensure that is properly used.

GNSS drivers implementation of serdev receive_buf() callback return
directly the return value of gnss_insert_raw(). gnss_insert_raw()
returns a signed int, however this is not an issue since the value
returned is always positive, because of the kfifo_in() implementation.
gnss_insert_raw() could be changed to return also an unsigned, however
this is not implemented here as request by the GNSS maintainer Johan
Hovold.

Suggested-by: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/all/087be419-ec6b-47ad-851a-5e1e3ea5cfcc@kernel.org/
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> #for-iio
Reviewed-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Alex Elder <elder@linaro.org>
Acked-by: Maximilian Luz <luzmaximilian@gmail.com> # for platform/surface
Acked-by: Lee Jones <lee@kernel.org>
Acked-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20240122180551.34429-1-francesco@dolcini.it
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: serdev: convert to u8 and size_t

Switch character types to u8 and sizes to size_t. To conform to
characters/sizes in the rest of the tty layer.

This patch converts struct serdev_device_ops hooks and its
instantiations.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Cc: Rob Herring <robh@kernel.org>
Acked-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20231206073712.17776-24-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

platform/surface: aggregator: fix recv_buf() return value

Serdev recv_buf() callback is supposed to return the amount of bytes
consumed, therefore an int in between 0 and count.

Do not return negative number in case of issue, when
ssam_controller_receive_buf() returns ESHUTDOWN just returns 0, e.g. no
bytes consumed, this keep the exact same behavior as it was before.

This fixes a potential WARN in serdev-ttyport.c:ttyport_receive_buf().

Fixes: c167b9c7e3d6 ("platform/surface: Add Surface Aggregator subsystem")
Cc: stable@vger.kernel.org
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Reviewed-by: Maximilian Luz <luzmaximilian@gmail.com>
Link: https://lore.kernel.org/r/20231128194935.11350-1-francesco@dolcini.it
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

platform/surface: Update copyright year of various drivers

Update the copyright of various Surface drivers to the current year.

Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
Link: https://lore.kernel.org/r/20220624205800.1355621-4-luzmaximilian@gmail.com
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

platform/surface: aggregator: Fix initialization order when compiling as builtin module

When building the Surface Aggregator Module (SAM) core, registry, and
other SAM client drivers as builtin modules (=y), proper initialization
order is not guaranteed. Due to this, client driver registration
(triggered by device registration in the registry) races against bus
initialization in the core.

If any attempt is made at registering the device driver before the bus
has been initialized (i.e. if bus initialization fails this race) driver
registration will fail with a message similar to:

Driver surface_battery was unable to register with bus_type surface_aggregator because the bus was not initialized

Switch from module_init() to subsys_initcall() to resolve this issue.
Note that the serdev subsystem uses postcore_initcall() so we are still
able to safely register the serdev device driver for the core.

Fixes: c167b9c7e3d6 ("platform/surface: Add Surface Aggregator subsystem")
Reported-by: Blaž Hrastnik <blaz@mxxn.io>
Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
Link: https://lore.kernel.org/r/20220429195738.535751-1-luzmaximilian@gmail.com
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

platform/surface: aggregator: Fix initialization order when compiling as builtin module

When building the Surface Aggregator Module (SAM) core, registry, and
other SAM client drivers as builtin modules (=y), proper initialization
order is not guaranteed. Due to this, client driver registration
(triggered by device registration in the registry) races against bus
initialization in the core.

If any attempt is made at registering the device driver before the bus
has been initialized (i.e. if bus initialization fails this race) driver
registration will fail with a message similar to:

Driver surface_battery was unable to register with bus_type surface_aggregator because the bus was not initialized

Switch from module_init() to subsys_initcall() to resolve this issue.
Note that the serdev subsystem uses postcore_initcall() so we are still
able to safely register the serdev device driver for the core.

Fixes: c167b9c7e3d6 ("platform/surface: Add Surface Aggregator subsystem")
Reported-by: Blaž Hrastnik <blaz@mxxn.io>
Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
Link: https://lore.kernel.org/r/20220429195738.535751-1-luzmaximilian@gmail.com
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

platform/surface: aggregator: Make client device removal more generic

Currently, there are similar functions defined in the Aggregator
Registry and the controller core.

Make client device removal more generic and export it. We can then use
this function later on to remove client devices from device hubs as well
as the controller and avoid re-defining similar things.

Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
Link: https://lore.kernel.org/r/20211028002243.1586083-2-luzmaximilian@gmail.com
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

platform/surface: aggregator: Use serdev_acpi_get_uart_resource() helper

serdev provides a generic helper to get UART Serial Bus resources.
Use it instead of an open coded variant.

Reviewed-by: Maximilian Luz <luzmaximilian@gmail.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20210806111736.66591-2-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

platform/surface: aggregator: Update copyright

It's 2021, update the copyright accordingly.

Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20210604134755.535590-4-luzmaximilian@gmail.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

ACPI: scan: Extend acpi_walk_dep_device_list()

The acpi_walk_dep_device_list() function is not as generic as its
name implies, serving only to decrement the dependency count for each
dependent device of the input.

Extend it to accept a callback which can be applied to all the
dependencies in acpi_dep_list.

Replace all existing calls to the function with calls to a wrapper,
passing a callback that applies the same dependency reduction.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Maximilian Luz <luzmaximilian@gmail.com> # for platform/surface parts
Signed-off-by: Daniel Scally <djrscally@gmail.com>
[ rjw: Changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

platform/surface: aggregator: Add dedicated bus and device type

The Surface Aggregator EC provides varying functionality, depending on
the Surface device. To manage this functionality, we use dedicated
client devices for each subsystem or virtual device of the EC. While
some of these clients are described as standard devices in ACPI and the
corresponding client drivers can be implemented as platform drivers in
the kernel (making use of the controller API already present), many
devices, especially on newer Surface models, cannot be found there.

To simplify management of these devices, we introduce a new bus and
client device type for the Surface Aggregator subsystem. The new device
type takes care of managing the controller reference, essentially
guaranteeing its validity for as long as the client device exists, thus
alleviating the need to manually establish device links for that purpose
in the client driver (as has to be done with the platform devices).

Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20201221183959.1186143-7-luzmaximilian@gmail.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

platform/surface: aggregator: Add trace points

Add trace points to the Surface Aggregator subsystem core. These trace
points can be used to track packets, requests, and allocations. They are
further intended for debugging and testing/validation, specifically in
combination with the error injection capabilities introduced in the
subsequent commit.

Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20201221183959.1186143-5-luzmaximilian@gmail.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

platform/surface: aggregator: Add event item allocation caching

Event items are used for completing Surface Aggregator EC events, i.e.
placing event command data and payload on a workqueue for later
processing to avoid doing said processing directly on the receiver
thread. This means that event items are allocated for each incoming
event, regardless of that event being transmitted via sequenced or
unsequenced packets.

On the Surface Book 3 and Surface Laptop 3, touchpad HID input events
(unsequenced), can constitute a larger amount of traffic, and therefore
allocation of event items. This warrants caching event items to reduce
memory fragmentation. The size of the cached objects is specifically
tuned to accommodate keyboard and touchpad input events and their
payloads on those devices. As a result, this effectively also covers
most other event types. In case of a larger event payload, event item
allocation will fall back to kzalloc().

Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20201221183959.1186143-4-luzmaximilian@gmail.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

platform/surface: aggregator: Add control packet allocation caching

Surface Serial Hub communication is, in its core, packet based. Each
sequenced packet requires to be acknowledged, via an ACK-type control
packet. In case invalid data has been received by the driver, a NAK-type
(not-acknowledge/negative acknowledge) control packet is sent,
triggering retransmission.

Control packets are therefore a core communication primitive and used
frequently enough (with every sequenced packet transmission sent by the
embedded controller, including events and request responses) that it may
warrant caching their allocations to reduce possible memory
fragmentation.

Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20201221183959.1186143-3-luzmaximilian@gmail.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

platform/surface: Add Surface Aggregator subsystem

Add Surface System Aggregator Module core and Surface Serial Hub driver,
required for the embedded controller found on Microsoft Surface devices.

The Surface System Aggregator Module (SSAM, SAM or Surface Aggregator)
is an embedded controller (EC) found on 4th and later generation
Microsoft Surface devices, with the exception of the Surface Go series.
This EC provides various functionality, depending on the device in
question. This can include battery status and thermal reporting (5th and
later generations), but also HID keyboard (6th+) and touchpad input
(7th+) on Surface Laptop and Surface Book 3 series devices.

This patch provides the basic necessities for communication with the SAM
EC on 5th and later generation devices. On these devices, the EC
provides an interface that acts as serial device, called the Surface
Serial Hub (SSH). 4th generation devices, on which the EC interface is
provided via an HID-over-I2C device, are not supported by this patch.

Specifically, this patch adds a driver for the SSH device (device HID
MSHW0084 in ACPI), as well as a controller structure and associated API.
This represents the functional core of the Surface Aggregator kernel
subsystem, introduced with this patch, and will be expanded upon in
subsequent commits.

The SSH driver acts as the main attachment point for this subsystem and
sets-up and manages the controller structure. The controller in turn
provides a basic communication interface, allowing to send requests from
host to EC and receiving the corresponding responses, as well as
managing and receiving events, sent from EC to host. It is structured
into multiple layers, with the top layer presenting the API used by
other kernel drivers and the lower layers modeled after the serial
protocol used for communication.

Said other drivers are then responsible for providing the (Surface model
specific) functionality accessible through the EC (e.g. battery status
reporting, thermal information, ...) via said controller structure and
API, and will be added in future commits.

Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
Link: https://lore.kernel.org/r/20201221183959.1186143-2-luzmaximilian@gmail.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>