Pull char/misc/IIO driver updates from Greg KH:
"Here is the big set of char/misc/iio and other smaller driver
subsystem changes for 7.0-rc1. Lots of little things in here,
including:
- Loads of iio driver changes and updates and additions
- gpib driver updates
- interconnect driver updates
- i3c driver updates
- hwtracing (coresight and intel) driver updates
- deletion of the obsolete mwave driver
- binder driver updates (rust and c versions)
- mhi driver updates (causing a merge conflict, see below)
- mei driver updates
- fsi driver updates
- eeprom driver updates
- lots of other small char and misc driver updates and cleanups
All of these have been in linux-next for a while, with no reported
issues"
* tag 'char-misc-7.0-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc: (297 commits)
mux: mmio: fix regmap leak on probe failure
rust_binder: return p from rust_binder_transaction_target_node()
drivers: android: binder: Update ARef imports from sync::aref
rust_binder: fix needless borrow in context.rs
iio: magn: mmc5633: Fix Kconfig for combination of I3C as module and driver builtin
iio: sca3000: Fix a resource leak in sca3000_probe()
iio: proximity: rfd77402: Add interrupt handling support
iio: proximity: rfd77402: Document device private data structure
iio: proximity: rfd77402: Use devm-managed mutex initialization
iio: proximity: rfd77402: Use kernel helper for result polling
iio: proximity: rfd77402: Align polling timeout with datasheet
iio: cros_ec: Allow enabling/disabling calibration mode
iio: frequency: ad9523: correct kernel-doc bad line warning
iio: buffer: buffer_impl.h: fix kernel-doc warnings
iio: gyro: itg3200: Fix unchecked return value in read_raw
MAINTAINERS: add entry for ADE9000 driver
iio: accel: sca3000: remove unused last_timestamp field
iio: accel: adxl372: remove unused int2_bitmask field
iio: adc: ad7766: Use iio_trigger_generic_data_rdy_poll()
iio: magnetometer: Remove IRQF_ONESHOT
...
There is currently an inconsistency between C and Rust, which is that
when Rust requires cfg(CONFIG_COMPAT) on compat_ioctl when using the
compat_ptr_ioctl symbol because '#define compat_ptr_ioctl NULL' does not
get translated to anything by bindgen.
But it's not *just* a matter of translating the '#define' into Rust when
CONFIG_COMPAT=n. This is because when CONFIG_COMPAT=y, the type of
compat_ptr_ioctl is a non-nullable function pointer, and to seamlessly
use it regardless of the config, we need a nullable function pointer.
I think it's important to do something about this; I've seen the mistake
of accidentally forgetting '#[cfg(CONFIG_COMPAT)]' when compat_ptr_ioctl
is used multiple times now.
This explicitly declares 'bindings::compat_ptr_ioctl' as an Option that
is always defined but might be None. This matches C, but isn't ideal:
it modifies the bindings crate. But I'm not sure if there's a better way
to do it. If we just redefine in kernel/, then people may still use the
one in bindings::, since that is where you would normally find it. I am
open to suggestions.
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260105-redefine-compat_ptr_ioctl-v1-1-25edb3d91acc@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
We're generally not proponents of rewrites (nasty uncomfortable things
that make you late for dinner!). So why rewrite Binder?
Binder has been evolving over the past 15+ years to meet the evolving
needs of Android. Its responsibilities, expectations, and complexity
have grown considerably during that time. While we expect Binder to
continue to evolve along with Android, there are a number of factors
that currently constrain our ability to develop/maintain it. Briefly
those are:
1. Complexity: Binder is at the intersection of everything in Android and
fulfills many responsibilities beyond IPC. It has become many things
to many people, and due to its many features and their interactions
with each other, its complexity is quite high. In just 6kLOC it must
deliver transactions to the right threads. It must correctly parse
and translate the contents of transactions, which can contain several
objects of different types (e.g., pointers, fds) that can interact
with each other. It controls the size of thread pools in userspace,
and ensures that transactions are assigned to threads in ways that
avoid deadlocks where the threadpool has run out of threads. It must
track refcounts of objects that are shared by several processes by
forwarding refcount changes between the processes correctly. It must
handle numerous error scenarios and it combines/nests 13 different
locks, 7 reference counters, and atomic variables. Finally, It must
do all of this as fast and efficiently as possible. Minor performance
regressions can cause a noticeably degraded user experience.
2. Things to improve: Thousand-line functions [1], error-prone error
handling [2], and confusing structure can occur as a code base grows
organically. After more than a decade of development, this codebase
could use an overhaul.
[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/android/binder.c?h=v6.5#n2896
[2]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/android/binder.c?h=v6.5#n3658
3. Security critical: Binder is a critical part of Android's sandboxing
strategy. Even Android's most de-privileged sandboxes (e.g. the
Chrome renderer, or SW Codec) have direct access to Binder. More than
just about any other component, it's important that Binder provide
robust security, and itself be robust against security
vulnerabilities.
It's #1 (high complexity) that has made continuing to evolve Binder and
resolving #2 (tech debt) exceptionally difficult without causing #3
(security issues). For Binder to continue to meet Android's needs, we
need better ways to manage (and reduce!) complexity without increasing
the risk.
The biggest change is obviously the choice of programming language. We
decided to use Rust because it directly addresses a number of the
challenges within Binder that we have faced during the last years. It
prevents mistakes with ref counting, locking, bounds checking, and also
does a lot to reduce the complexity of error handling. Additionally,
we've been able to use the more expressive type system to encode the
ownership semantics of the various structs and pointers, which takes the
complexity of managing object lifetimes out of the hands of the
programmer, reducing the risk of use-after-frees and similar problems.
Rust has many different pointer types that it uses to encode ownership
semantics into the type system, and this is probably one of the most
important aspects of how it helps in Binder. The Binder driver has a lot
of different objects that have complex ownership semantics; some
pointers own a refcount, some pointers have exclusive ownership, and
some pointers just reference the object and it is kept alive in some
other manner. With Rust, we can use a different pointer type for each
kind of pointer, which enables the compiler to enforce that the
ownership semantics are implemented correctly.
Another useful feature is Rust's error handling. Rust allows for more
simplified error handling with features such as destructors, and you get
compilation failures if errors are not properly handled. This means that
even though Rust requires you to spend more lines of code than C on
things such as writing down invariants that are left implicit in C, the
Rust driver is still slightly smaller than C binder: Rust is 5.5kLOC and
C is 5.8kLOC. (These numbers are excluding blank lines, comments,
binderfs, and any debugging facilities in C that are not yet implemented
in the Rust driver. The numbers include abstractions in rust/kernel/
that are unlikely to be used by other drivers than Binder.)
Although this rewrite completely rethinks how the code is structured and
how assumptions are enforced, we do not fundamentally change *how* the
driver does the things it does. A lot of careful thought has gone into
the existing design. The rewrite is aimed rather at improving code
health, structure, readability, robustness, security, maintainability
and extensibility. We also include more inline documentation, and
improve how assumptions in the code are enforced. Furthermore, all
unsafe code is annotated with a SAFETY comment that explains why it is
correct.
We have left the binderfs filesystem component in C. Rewriting it in
Rust would be a large amount of work and requires a lot of bindings to
the file system interfaces. Binderfs has not historically had the same
challenges with security and complexity, so rewriting binderfs seems to
have lower value than the rest of Binder.
Correctness and feature parity
------------------------------
Rust binder passes all tests that validate the correctness of Binder in
the Android Open Source Project. We can boot a device, and run a variety
of apps and functionality without issues. We have performed this both on
the Cuttlefish Android emulator device, and on a Pixel 6 Pro.
As for feature parity, Rust binder currently implements all features
that C binder supports, with the exception of some debugging facilities.
The missing debugging facilities will be added before we submit the Rust
implementation upstream.
Tracepoints
-----------
I did not include all of the tracepoints as I felt that the mechansim
for making C access fields of Rust structs should be discussed on list
separately. I also did not include the support for building Rust Binder
as a module since that requires exporting a bunch of additional symbols
on the C side.
Original RFC Link with old benchmark numbers:
https://lore.kernel.org/r/20231101-rust-binder-v1-0-08ba9197f637@google.com
Co-developed-by: Wedson Almeida Filho <wedsonaf@gmail.com>
Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
Co-developed-by: Matt Gilbride <mattgilbride@google.com>
Signed-off-by: Matt Gilbride <mattgilbride@google.com>
Acked-by: Carlos Llamas <cmllamas@google.com>
Acked-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20250919-rust-binder-v2-1-a384b09f28dd@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
