rust: device: rename "Device::from_raw()"

[PATCH v3 0/1] rust: device: rename "Device::from_raw()"

Posted by Guilherme Giacomo Simoes 1 month, 4 weeks ago

Why did I make this change?
This function "Device::from_raw()" increments the refcount by this
command "bindings::get_device(prt)". This can be confused because the
function Arc::from_raw() from the standard library, doesn't increment
the refcount.

This discussion is in
https://rust-for-linux.zulipchat.com/#narrow/stream/291566-Library/topic/Inconsistency.20of.20.60from_raw.60.2E

The options can be:
1) Rename the function for don't make confusing with the
Arc::from_raw().
2) Remove this function and use the unsafe { Device::as_ref(ptr)
}.into() when I need the get pointer for the device.

Proposed solution
I like the first option. Because, how was will commented by Boqun Feng ,
when the people write the "unsafe { Device::as_ref(ptr) }.into()" again,
again and again... inevitably anybody will create a help function for
this.

Then I think that we should rename this function for
Device::get_from_raw() or maybe Device::get_device() and I like more of
the second option because, this will be equal the get_device() function
that already exists in .c code.


How do I test this:
I create this simple file in sample/rust/device.rs
""""""""
use kernel::device::Device;
use kernel::prelude::*;
use kernel::types::ARef;

module! {
    type: DeviceTest,
    name: "device_test",
    author: "Test device",
    description: "A simple module for test device",
    license: "GPL",
}

struct DeviceTest;

impl kernel::Module for DeviceTest {
    fn init(_module: &'static ThisModule) -> Result<Self> {
        pr_info!("initial device test");
        let device = create_and_get_device();
        pr_info!("device created");

        Ok(DeviceTest)
    }
}

impl Drop for DeviceTest {
    fn drop(&mut self) {
        pr_info!("bye bye driver test");
    }
}

fn create_and_get_device() -> ARef<Device> {
    let device = unsafe { Device::get_device(core::ptr::null_mut()) };
    device
}
""""""""

I set this in Kconfig
diff --git a/samples/rust/Kconfig b/samples/rust/Kconfig
index b0f74a81c8f9..7779969e7dd6 100644
--- a/samples/rust/Kconfig
+++ b/samples/rust/Kconfig
@@ -37,4 +37,9 @@ config SAMPLE_RUST_HOSTPROGS

          If unsure, say N.

+config SAMPLE_DEVICE_TEST
+       tristate "Device test"
+       help
+               This option is for device test
+
 endif # SAMPLES_RUST


and in Makefile
diff --git a/samples/rust/Makefile b/samples/rust/Makefile
index 03086dabbea4..85a8b30100e7 100644
--- a/samples/rust/Makefile
+++ b/samples/rust/Makefile
@@ -2,5 +2,6 @@

 obj-$(CONFIG_SAMPLE_RUST_MINIMAL)              += rust_minimal.o
 obj-$(CONFIG_SAMPLE_RUST_PRINT)                        += rust_print.o
+obj-$(CONFIG_SAMPLE_DEVICE_TEST)                       += device.o

 subdir-$(CONFIG_SAMPLE_RUST_HOSTPROGS)         += hostprogs


Then I enable this in menu config... compile the kernel e run this in a
qemu:
qemu-system-x86_64 -kernel bzImage -initrd initramfs.img -m 2G -machine
q35 -device ich9-ahci,id=sata -drive
id=disk,file=rootfs.img,if=none,format=raw -device
ide-hd,drive=disk,bus=sata.0 -append "root=/dev/sda console=ttyS0"
-nographic -monitor telnet:127.0.0.1:5555,server,nowai

the expected print is showing
[    2.786174] device_test: initial device test
[    2.786541] device_test: device created


Guilherme Giacomo Simoes (1):
  rust: device: rename "Device::from_raw()"

 rust/kernel/device.rs   | 2 +-
 rust/kernel/firmware.rs | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

-- 

Changes from v2:
 - Refactored commit message style

[PATCH v3 1/1] rust: device: rename "Device::from_raw()"

Posted by Guilherme Giacomo Simoes 1 month, 4 weeks ago

This function increments the refcount by a call to
"bindings::get_device(ptr)". This can be confused because, the function
Arch::from_raw() from standard library, don't increments the refcount.
Hence, rename "Device::from_raw()" to avoid confusion with other
"from_raw" semantics.

Signed-off-by: Guilherme Giacomo Simoes <trintaeoitogc@gmail.com>
---
 rust/kernel/device.rs   | 2 +-
 rust/kernel/firmware.rs | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
index 851018eef885..ecffaff041e0 100644
--- a/rust/kernel/device.rs
+++ b/rust/kernel/device.rs
@@ -51,7 +51,7 @@ impl Device {
     ///
     /// It must also be ensured that `bindings::device::release` can be called from any thread.
     /// While not officially documented, this should be the case for any `struct device`.
-    pub unsafe fn from_raw(ptr: *mut bindings::device) -> ARef<Self> {
+    pub unsafe fn get_device(ptr: *mut bindings::device) -> ARef<Self> {
         // SAFETY: By the safety requirements, ptr is valid.
         // Initially increase the reference count by one to compensate for the final decrement once
         // this newly created `ARef<Device>` instance is dropped.
diff --git a/rust/kernel/firmware.rs b/rust/kernel/firmware.rs
index dee5b4b18aec..13a374a5cdb7 100644
--- a/rust/kernel/firmware.rs
+++ b/rust/kernel/firmware.rs
@@ -44,7 +44,7 @@ fn request_nowarn() -> Self {
 ///
 /// # fn no_run() -> Result<(), Error> {
 /// # // SAFETY: *NOT* safe, just for the example to get an `ARef<Device>` instance
-/// # let dev = unsafe { Device::from_raw(core::ptr::null_mut()) };
+/// # let dev = unsafe { Device::get_device(core::ptr::null_mut()) };
 ///
 /// let fw = Firmware::request(c_str!("path/to/firmware.bin"), &dev)?;
 /// let blob = fw.data();
-- 
2.46.2