From nobody Thu Oct 2 22:52:48 2025 Received: from forward202b.mail.yandex.net (forward202b.mail.yandex.net [178.154.239.155]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E3275304BB5; Tue, 9 Sep 2025 12:39:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=178.154.239.155 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757421548; cv=none; b=REz6lMgWlmDMHGwzgzYt8dj3FRyF4qCvy5ciuIKIeNIF9K77S5qxWFhrbIcnIj6YNXbIxMQ7u7xT/wYIoA9cfDmUu7Hvf2Umq4XgqwQK7K6pfCO4Ftu98tRcLSN6Frb84rD3ub8Mc+Dil1hGPMsr7E9yY1cipd5Emq2sdyTd6ak= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757421548; c=relaxed/simple; bh=2owVnM9T2ch2QOHSkKCCLGPL8B2GMtCZYv94bswQSFg=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:Content-Type; b=JQQxWV22x/5lzSDHw+5PgduleGhdhl1za6/eQMrYCN+KYsLVtxPwh63wALi+xdTH+7h3/Mo3sZyaLVPl6GKqDys5U8CrfOxHsFBjadR/DJxK0I6SH7297QHW1njXt2bRyOX1kyMos1QY8d+Up/57tt+pMIJ7J8h0dOWlpGtbr2A= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=onurozkan.dev; spf=pass smtp.mailfrom=onurozkan.dev; dkim=pass (1024-bit key) header.d=onurozkan.dev header.i=@onurozkan.dev header.b=PzrijJde; arc=none smtp.client-ip=178.154.239.155 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=onurozkan.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=onurozkan.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=onurozkan.dev header.i=@onurozkan.dev header.b="PzrijJde" Received: from forward101b.mail.yandex.net (forward101b.mail.yandex.net [IPv6:2a02:6b8:c02:900:1:45:d181:d101]) by forward202b.mail.yandex.net (Yandex) with ESMTPS id 51306C47A2; Tue, 09 Sep 2025 15:33:25 +0300 (MSK) Received: from mail-nwsmtp-smtp-production-main-60.sas.yp-c.yandex.net (mail-nwsmtp-smtp-production-main-60.sas.yp-c.yandex.net [IPv6:2a02:6b8:c23:4419:0:640:5be6:0]) by forward101b.mail.yandex.net (Yandex) with ESMTPS id 432EBC0107; Tue, 09 Sep 2025 15:33:16 +0300 (MSK) Received: by mail-nwsmtp-smtp-production-main-60.sas.yp-c.yandex.net (smtp/Yandex) with ESMTPSA id 1XIUaq3MuSw0-RtwQoMEU; Tue, 09 Sep 2025 15:33:15 +0300 X-Yandex-Fwd: 1 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=onurozkan.dev; s=mail; t=1757421195; bh=m3qbGzn73yAfuqNuP1WFEZRME95KM0396p1UpUOU0Oc=; h=Message-ID:Date:Cc:Subject:To:From; b=PzrijJdeJB94GF+lxpIJnNXyW5rGxezLdWCGtdcWD2peX24zdAMAxYP0b8Ezupbzb OxRoCG6ep4m+2WTivrtgr6H21wGPZ7ujKZQlU+cT8jOJ3jGtjDLBFpcCaQRW5ehs2o eEqnF9J7rK8ADM+J7DQ00prCePxVe+0GkRK17ark= Authentication-Results: mail-nwsmtp-smtp-production-main-60.sas.yp-c.yandex.net; dkim=pass header.i=@onurozkan.dev From: =?UTF-8?q?Onur=20=C3=96zkan?= To: rust-for-linux@vger.kernel.org Cc: linux-kernel@vger.kernel.org, daniel@sedlak.dev, dirk.behme@de.bosch.com, felipe_life@live.com, tamird@gmail.com, dakr@kernel.org, tmgross@umich.edu, aliceryhl@google.com, a.hindborg@kernel.org, lossin@kernel.org, bjorn3_gh@protonmail.com, gary@garyguo.net, boqun.feng@gmail.com, alex.gaynor@gmail.com, ojeda@kernel.org, =?UTF-8?q?Onur=20=C3=96zkan?= Subject: [PATCH v1] rust: refactor `to_result` to return the original value Date: Tue, 9 Sep 2025 15:32:58 +0300 Message-ID: <20250909123258.29304-1-work@onurozkan.dev> X-Mailer: git-send-email 2.50.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Current `to_result` helper takes a `c_int` and returns `Ok(())` on success and this has some issues like: - Callers lose the original return value and often have to store it in a temporary variable before calling `to_result`. - It only supports `c_int`, which makes callers to unnecessarily cast when working with other types (e.g. `u16` in phy abstractions). We even have some places that ignore to use `to_result` helper because the input doesn't fit in `c_int` (see [0]). [0]: https://lore.kernel.org/all/20250822080252.773d6f54@nimda.home/ This patch changes `to_result` to be generic and also return the original value on success. So that the code that previously looked like: let ret =3D unsafe { bindings::some_ffi_call() }; to_result(ret).map(|()| SomeType::new(ret)) can now be written more directly as: to_result(unsafe { bindings::some_ffi_call() }) .map(|ret| SomeType::new(ret)) Similarly, code such as: let res: isize =3D $some_ffi_call(); if res < 0 { return Err(Error::from_errno(res as i32)); } can now be used with `to_result` as: to_result($some_ffi_call())?; Existing call sites that only care about success/failure are updated to append `.map(|_| ())` to preserve their previous semantics. They can also use the equivalent pattern: to_result($something)?; Ok(()) This patch only fixes the callers that broke after the changes on `to_resul= t`. I haven't included all the improvements made possible by the new design sin= ce that could conflict with other ongoing patches [1]. Once this patch is appr= oved and applied, I am planning to follow up with creating a "good first issue" = on [2] for those additional changes. [1]: https://lore.kernel.org/rust-for-linux/?q=3Dto_result [2]: https://github.com/Rust-for-Linux/linux Link: https://rust-for-linux.zulipchat.com/#narrow/channel/288089/topic/x/n= ear/536374456 Signed-off-by: Onur =C3=96zkan --- rust/kernel/auxiliary.rs | 1 + rust/kernel/block/mq/tag_set.rs | 2 +- rust/kernel/cpufreq.rs | 3 ++- rust/kernel/devres.rs | 1 + rust/kernel/dma.rs | 3 +++ rust/kernel/error.rs | 17 ++++++++++++----- rust/kernel/miscdevice.rs | 2 +- rust/kernel/mm/virt.rs | 1 + rust/kernel/pci.rs | 3 ++- rust/kernel/platform.rs | 2 +- rust/kernel/regulator.rs | 5 +++-- 11 files changed, 28 insertions(+), 12 deletions(-) diff --git a/rust/kernel/auxiliary.rs b/rust/kernel/auxiliary.rs index 4749fb6bffef..479c0ad2a572 100644 --- a/rust/kernel/auxiliary.rs +++ b/rust/kernel/auxiliary.rs @@ -43,6 +43,7 @@ unsafe fn register( to_result(unsafe { bindings::__auxiliary_driver_register(adrv.get(), module.0, na= me.as_char_ptr()) }) + .map(|_| ()) } unsafe fn unregister(adrv: &Opaque) { diff --git a/rust/kernel/block/mq/tag_set.rs b/rust/kernel/block/mq/tag_set= .rs index c3cf56d52bee..0e7883163000 100644 --- a/rust/kernel/block/mq/tag_set.rs +++ b/rust/kernel/block/mq/tag_set.rs @@ -65,7 +65,7 @@ pub fn new( // SAFETY: we do not move out of `tag_set`. let tag_set: &mut Opaque<_> =3D unsafe { Pin::get_unchecke= d_mut(tag_set) }; // SAFETY: `tag_set` is a reference to an initialized `blk= _mq_tag_set`. - error::to_result( unsafe { bindings::blk_mq_alloc_tag_set(= tag_set.get())}) + error::to_result( unsafe { bindings::blk_mq_alloc_tag_set(= tag_set.get())}).map(|_| ()) }), _p: PhantomData, }) diff --git a/rust/kernel/cpufreq.rs b/rust/kernel/cpufreq.rs index be2dffbdb546..c3fa20ce229a 100644 --- a/rust/kernel/cpufreq.rs +++ b/rust/kernel/cpufreq.rs @@ -157,6 +157,7 @@ pub fn as_raw(&self) -> *mut bindings::cpufreq_policy_d= ata { pub fn generic_verify(&self) -> Result { // SAFETY: By the type invariant, the pointer stored in `self` is = valid. to_result(unsafe { bindings::cpufreq_generic_frequency_table_verif= y(self.as_raw()) }) + .map(|_| ()) } } @@ -519,7 +520,7 @@ pub fn set_suspend_freq(&mut self, freq: Hertz) -> &mut= Self { #[inline] pub fn generic_suspend(&mut self) -> Result { // SAFETY: By the type invariant, the pointer stored in `self` is = valid. - to_result(unsafe { bindings::cpufreq_generic_suspend(self.as_mut_r= ef()) }) + to_result(unsafe { bindings::cpufreq_generic_suspend(self.as_mut_r= ef()) }).map(|_| ()) } /// Provides a wrapper to the generic get routine. diff --git a/rust/kernel/devres.rs b/rust/kernel/devres.rs index d04e3fcebafb..214cd9a0ebe0 100644 --- a/rust/kernel/devres.rs +++ b/rust/kernel/devres.rs @@ -328,6 +328,7 @@ fn register_foreign

(dev: &Device, data: P) ->= Result // `ForeignOwnable` is released eventually. bindings::devm_add_action_or_reset(dev.as_raw(), Some(callback::), ptr.cast()) }) + .map(|_| ()) } /// Encapsulate `data` in a [`KBox`] and [`Drop::drop`] `data` once `dev` = is unbound. diff --git a/rust/kernel/dma.rs b/rust/kernel/dma.rs index 68fe67624424..f614453ddb7d 100644 --- a/rust/kernel/dma.rs +++ b/rust/kernel/dma.rs @@ -34,6 +34,7 @@ unsafe fn dma_set_mask(&self, mask: DmaMask) -> Result { // - The safety requirement of this function guarantees that there= are no concurrent calls // to DMA allocation and mapping primitives using this mask. to_result(unsafe { bindings::dma_set_mask(self.as_ref().as_raw(), = mask.value()) }) + .map(|_| ()) } /// Set up the device's DMA coherent addressing capabilities. @@ -51,6 +52,7 @@ unsafe fn dma_set_coherent_mask(&self, mask: DmaMask) -> = Result { // - The safety requirement of this function guarantees that there= are no concurrent calls // to DMA allocation and mapping primitives using this mask. to_result(unsafe { bindings::dma_set_coherent_mask(self.as_ref().a= s_raw(), mask.value()) }) + .map(|_| ()) } /// Set up the device's DMA addressing capabilities. @@ -72,6 +74,7 @@ unsafe fn dma_set_mask_and_coherent(&self, mask: DmaMask)= -> Result { to_result(unsafe { bindings::dma_set_mask_and_coherent(self.as_ref().as_raw(), ma= sk.value()) }) + .map(|_| ()) } } diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs index db14da976722..f76afa4b7ec1 100644 --- a/rust/kernel/error.rs +++ b/rust/kernel/error.rs @@ -378,12 +378,19 @@ fn from(e: core::convert::Infallible) -> Error { pub type Result =3D core::result::Result; /// Converts an integer as returned by a C kernel function to an error if = it's negative, and -/// `Ok(())` otherwise. -pub fn to_result(err: crate::ffi::c_int) -> Result { - if err < 0 { - Err(Error::from_errno(err)) +/// returns the original value otherwise. +pub fn to_result(code: T) -> Result +where + T: Copy + TryInto, +{ + // Try casting into `i32`. + let casted: crate::ffi::c_int =3D code.try_into().unwrap_or(0); + + if casted < 0 { + Err(Error::from_errno(casted)) } else { - Ok(()) + // Return the original input value. + Ok(code) } } diff --git a/rust/kernel/miscdevice.rs b/rust/kernel/miscdevice.rs index 6373fe183b27..22b72ae84c03 100644 --- a/rust/kernel/miscdevice.rs +++ b/rust/kernel/miscdevice.rs @@ -79,7 +79,7 @@ pub fn register(opts: MiscDeviceOptions) -> impl PinInit<= Self, Error> { // the destructor of this type deallocates the memory. // INVARIANT: If this returns `Ok(())`, then the `slot` wi= ll contain a registered // misc device. - to_result(unsafe { bindings::misc_register(slot) }) + to_result(unsafe { bindings::misc_register(slot) }).map(|_= | ()) }), _t: PhantomData, }) diff --git a/rust/kernel/mm/virt.rs b/rust/kernel/mm/virt.rs index a1bfa4e19293..5494f96e91b0 100644 --- a/rust/kernel/mm/virt.rs +++ b/rust/kernel/mm/virt.rs @@ -195,6 +195,7 @@ pub fn vm_insert_page(&self, address: usize, page: &Pag= e) -> Result { // SAFETY: By the type invariant of `Self` caller has read access = and has verified that // `VM_MIXEDMAP` is set. By invariant on `Page` the page has order= 0. to_result(unsafe { bindings::vm_insert_page(self.as_ptr(), address= , page.as_ptr()) }) + .map(|_| ()) } } diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs index 887ee611b553..6e917752cb89 100644 --- a/rust/kernel/pci.rs +++ b/rust/kernel/pci.rs @@ -48,6 +48,7 @@ unsafe fn register( to_result(unsafe { bindings::__pci_register_driver(pdrv.get(), module.0, name.as_= char_ptr()) }) + .map(|_| ()) } unsafe fn unregister(pdrv: &Opaque) { @@ -437,7 +438,7 @@ impl Device { /// Enable memory resources for this device. pub fn enable_device_mem(&self) -> Result { // SAFETY: `self.as_raw` is guaranteed to be a pointer to a valid = `struct pci_dev`. - to_result(unsafe { bindings::pci_enable_device_mem(self.as_raw()) = }) + to_result(unsafe { bindings::pci_enable_device_mem(self.as_raw()) = }).map(|_| ()) } /// Enable bus-mastering for this device. diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs index 8f028c76f9fa..5a5561c7326e 100644 --- a/rust/kernel/platform.rs +++ b/rust/kernel/platform.rs @@ -54,7 +54,7 @@ unsafe fn register( } // SAFETY: `pdrv` is guaranteed to be a valid `RegType`. - to_result(unsafe { bindings::__platform_driver_register(pdrv.get()= , module.0) }) + to_result(unsafe { bindings::__platform_driver_register(pdrv.get()= , module.0) }).map(|_| ()) } unsafe fn unregister(pdrv: &Opaque) { diff --git a/rust/kernel/regulator.rs b/rust/kernel/regulator.rs index 65f3a125348f..e17ae6e9a990 100644 --- a/rust/kernel/regulator.rs +++ b/rust/kernel/regulator.rs @@ -261,6 +261,7 @@ pub fn set_voltage(&self, min_voltage: Voltage, max_vol= tage: Voltage) -> Result max_voltage.as_microvolts(), ) }) + .map(|_| ()) } /// Gets the current voltage of the regulator. @@ -291,12 +292,12 @@ fn get_internal(dev: &Device, name: &CStr) -> Result<= Regulator> { fn enable_internal(&mut self) -> Result { // SAFETY: Safe as per the type invariants of `Regulator`. - to_result(unsafe { bindings::regulator_enable(self.inner.as_ptr())= }) + to_result(unsafe { bindings::regulator_enable(self.inner.as_ptr())= }).map(|_| ()) } fn disable_internal(&mut self) -> Result { // SAFETY: Safe as per the type invariants of `Regulator`. - to_result(unsafe { bindings::regulator_disable(self.inner.as_ptr()= ) }) + to_result(unsafe { bindings::regulator_disable(self.inner.as_ptr()= ) }).map(|_| ()) } } -- 2.50.0