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File descriptors should generally provide a fops->show_fdinfo() hook for
debugging purposes. Thus, add such a hook to the miscdevice
abstractions.
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20241203-miscdevice-showfdinfo-v1-1-7e990732d430@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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There are situations where a pointer to a `struct device` will become
necessary (e.g. for calling into dev_*() functions). This accessor
allows callers to pull this out from the `struct miscdevice`.
Signed-off-by: Lee Jones <lee@kernel.org>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Tested-by: Lee Jones <lee@kernel.org>
Reviewed-by: Danilo Krummrich <dakr@kernel.org>
Link: https://lore.kernel.org/r/20241210-miscdevice-file-param-v3-3-b2a79b666dc5@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Providing access to the underlying `struct miscdevice` is useful for
various reasons. For example, this allows you access the miscdevice's
internal `struct device` for use with the `dev_*` printing macros.
Note that since the underlying `struct miscdevice` could get freed at
any point after the fops->open() call (if misc_deregister is called),
only the open call is given access to it. To use `dev_*` printing macros
from other fops hooks, take a refcount on `miscdevice->this_device` to
keep it alive. See the linked thread for further discussion on the
lifetime of `struct miscdevice`.
Link: https://lore.kernel.org/r/2024120951-botanist-exhale-4845@gregkh
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Lee Jones <lee@kernel.org>
Tested-by: Lee Jones <lee@kernel.org>
Reviewed-by: Danilo Krummrich <dakr@kernel.org>
Link: https://lore.kernel.org/r/20241210-miscdevice-file-param-v3-2-b2a79b666dc5@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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This allows fops to access information about the underlying struct file
for the miscdevice. For example, the Binder driver needs to inspect the
O_NONBLOCK flag inside the fops->ioctl() hook.
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Lee Jones <lee@kernel.org>
Tested-by: Lee Jones <lee@kernel.org>
Reviewed-by: Danilo Krummrich <dakr@kernel.org>
Link: https://lore.kernel.org/r/20241210-miscdevice-file-param-v3-1-b2a79b666dc5@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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This fixes the following four warnings:
warning: unsafe block missing a safety comment
--> /home/aliceryhl/rust-for-linux/rust/kernel/miscdevice.rs:168:15
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168 | ..unsafe { MaybeUninit::zeroed().assume_init() }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= help: consider adding a safety comment on the preceding line
= help: for further information visit
https://rust-lang.github.io/rust-clippy/master/index.html#undocumented_unsafe_blocks
= note: requested on the command line with `-W clippy::undocumented-unsafe-blocks`
warning: unsafe function's docs are missing a `# Safety` section
--> /home/aliceryhl/rust-for-linux/rust/kernel/miscdevice.rs:175:1
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175 | / unsafe extern "C" fn fops_open<T: MiscDevice>(
176 | | inode: *mut bindings::inode,
177 | | file: *mut bindings::file,
178 | | ) -> c_int {
| |__________^
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= help: for further information visit
https://rust-lang.github.io/rust-clippy/master/index.html#missing_safety_doc
= note: `-W clippy::missing-safety-doc` implied by `-W clippy::all`
= help: to override `-W clippy::all` add `#[allow(clippy::missing_safety_doc)]`
warning: unsafe function's docs are missing a `# Safety` section
--> /home/aliceryhl/rust-for-linux/rust/kernel/miscdevice.rs:196:1
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196 | / unsafe extern "C" fn fops_release<T: MiscDevice>(
197 | | _inode: *mut bindings::inode,
198 | | file: *mut bindings::file,
199 | | ) -> c_int {
| |__________^
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= help: for further information visit
https://rust-lang.github.io/rust-clippy/master/index.html#missing_safety_doc
warning: unsafe function's docs are missing a `# Safety` section
--> /home/aliceryhl/rust-for-linux/rust/kernel/miscdevice.rs:210:1
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210 | / unsafe extern "C" fn fops_ioctl<T: MiscDevice>(
211 | | file: *mut bindings::file,
212 | | cmd: c_uint,
213 | | arg: c_ulong,
214 | | ) -> c_long {
| |___________^
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= help: for further information visit
https://rust-lang.github.io/rust-clippy/master/index.html#missing_safety_doc
Note that these warnings are currently not enabled in the build, but
rust-next contains a commit that will enable them, so we should fix
them.
Reported-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Closes: https://lore.kernel.org/rust-for-linux/CANiq72kOs6vPDUzZttQNqePFHphCQ30iVmZ5MO7eCJfPG==Vzg@mail.gmail.com/
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://lore.kernel.org/r/20241022-miscdevice-unsafe-warn-fix-v1-1-a78fde1740d6@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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When building miscdevice with clippy warnings, the following warning is
emitted:
warning: casting to the same type is unnecessary (`u32` -> `u32`)
--> /home/aliceryhl/rust-for-linux/rust/kernel/miscdevice.rs:220:28
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220 | match T::ioctl(device, cmd as u32, arg as usize) {
| ^^^^^^^^^^ help: try: `cmd`
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= help: for further information visit
https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
= note: `-W clippy::unnecessary-cast` implied by `-W clippy::all`
= help: to override `-W clippy::all` add `#[allow(clippy::unnecessary_cast)]`
Thus, fix it.
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20241015-miscdevice-cint-cast-v1-1-fcf4b75700ac@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Provide a `MiscDevice` trait that lets you specify the file operations
that you wish to provide for your misc device. For now, only three file
operations are provided: open, close, ioctl.
These abstractions only support MISC_DYNAMIC_MINOR. This enforces that
new miscdevices should not hard-code a minor number.
When implementing ioctl, the Result type is used. This means that you
can choose to return either of:
* An integer of type isize.
* An errno using the kernel::error::Error type.
When returning an isize, the integer is returned verbatim. It's mainly
intended for returning positive integers to userspace. However, it is
technically possible to return errors via the isize return value too.
To avoid having a dependency on files, this patch does not provide the
file operations callbacks a pointer to the file. This means that they
cannot check file properties such as O_NONBLOCK (which Binder needs).
Support for that can be added as a follow-up.
To avoid having a dependency on vma, this patch does not provide any way
to implement mmap (which Binder needs). Support for that can be added as
a follow-up.
Rust Binder will use these abstractions to create the /dev/binder file
when binderfs is disabled.
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/rust-for-linux/20240328195457.225001-1-wedsonaf@gmail.com/
Link: https://lore.kernel.org/r/20241001-b4-miscdevice-v2-2-330d760041fa@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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