From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3B81BC61DB9 for ; Thu, 27 Aug 2026 09:32:35 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 50AE510EF57; Thu, 27 Aug 2026 09:32:34 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=google.com header.i=@google.com header.b="eMvUWjFs"; dkim-atps=neutral Received: from mail-wr1-f71.google.com (mail-wr1-f71.google.com [209.85.221.71]) by gabe.freedesktop.org (Postfix) with ESMTPS id D253210EF45 for ; Thu, 27 Aug 2026 09:32:32 +0000 (UTC) Received: by mail-wr1-f71.google.com with SMTP id ffacd0b85a97d-482a2d55c4eso989348f8f.3 for ; Thu, 27 Aug 2026 02:32:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1787823151; x=1788427951; darn=lists.freedesktop.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=EOVo/FTydc/3lTq5xwei4nbCv9MVREwBkwBRQhpC8zc=; b=eMvUWjFsAkuVlTJxVHYAY8kkKDPgIHB6f2g3JWGToly5qjG/1XfEF+19ZY+CogkNH5 aHJVaQVP3d0kuhpi7tz/1RuVqKMgmXd2MxO61aTq+kIkFk58pFTL3dmxdvXQjcZ/lBYs aU9FurgM/JeI9loQL1S+Ibz7kFyU37aVnDMHa0A16kRMEH3SVX4a8Suxg1z3RjhOd5zF IIo2X3REh/2wJ6+oNlZ25OW9SCfnLcCfQfoDn4VYE/k2DmCr2rt+LQRI2uhqSE7uMnvO ivXOkknmuFXRoUZkvNIp3iFhrZ3TgZSFbPFQ8U878hwbS1H4RC4CHRkYCv0P1tSy0SGD jflA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1787823151; x=1788427951; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=EOVo/FTydc/3lTq5xwei4nbCv9MVREwBkwBRQhpC8zc=; b=A4am0HqNaHjiyHdv49+zIoJ0ECMezYjcxJi7W4qCFHw+fE5k4aDsw41dGaf9fYBlrM x9y1D2FTe7MTwtgVmKjiRLszzpIM70IaL+fIxZJFq+P7UCjCyA1CnPnvkr84fLlXRdcv uKm7ysb5Alyy+5Jp7HHvGkzLZ3UslJ4w5b4BzWIn22bCbjC0g08+ECLi5aYtSiKrOTOB s6KcT+AKbRxcJ72oL+wQFSd31KAvsrE9ALY09BT/mOT0vkaMJRtvwJr10vBoCqp1npnr RwzZ73pOzSuDhKEQaQ16lIzarcsr5js2KxUg0hLZMbwQdAwxo/Rhj7CmNDnJcKGKcnfg bc0A== X-Forwarded-Encrypted: i=1; AHgh+RpMHSK1ZdztuaVEMGFL8BNf34QrX7EdqLZyMJ+7vSO114jLFYUlNRW6RiRgeV+Um4841lRK7ZMS7B8=@lists.freedesktop.org X-Gm-Message-State: AFuF++loasEeU6PwU4ckuU58WyVIXAEqFNnMvL0E6puyAKjvtglCeZ+v 3tYaHLgQp+YR7JohdAqahgoaW4TpbEItKJySwjfCDGU/+2I76yN+tijzmen5fPvR3IEzJLAunlc ICULthNaYekVp106I9A== X-Received: from wrck21.prod.google.com ([2002:a5d:5255:0:b0:47f:6d55:abcd]) (user=aliceryhl job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6000:41fd:b0:47f:95e8:2ebf with SMTP id ffacd0b85a97d-482e26f8466mr17865060f8f.12.1787823150366; Thu, 27 Aug 2026 02:32:30 -0700 (PDT) Date: Thu, 27 Aug 2026 09:32:27 +0000 In-Reply-To: <20260827-chid-v8-3-bc74c77d0214@nvidia.com> Mime-Version: 1.0 References: <20260827-chid-v8-0-bc74c77d0214@nvidia.com> <20260827-chid-v8-3-bc74c77d0214@nvidia.com> Message-ID: Subject: Re: [PATCH v8 03/12] rust: num: add cv! macro to create values from constant expressions From: Alice Ryhl To: Eliot Courtney Cc: Burak Emir , Yury Norov , Miguel Ojeda , Boqun Feng , Gary Guo , "=?utf-8?B?QmrDtnJu?= Roy Baron" , Benno Lossin , Andreas Hindborg , Trevor Gross , Danilo Krummrich , Daniel Almeida , Tamir Duberstein , Alexandre Courbot , "Onur =?utf-8?B?w5Z6a2Fu?=" , David Airlie , Simona Vetter , Greg Kroah-Hartman , John Hubbard , Alistair Popple , Timur Tabi , Zhi Wang , rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, nova-gpu@lists.linux.dev, dri-devel@lists.freedesktop.org Content-Type: text/plain; charset="utf-8" X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Thu, Aug 27, 2026 at 04:28:31PM +0900, Eliot Courtney wrote: > Currently, using NonZero/Bounded constants is quite verbose. It's > unfortunate because it disincentivizes using it in interface boundaries. > Introduce a macro to make it nicer to use. The macro `cv!` (for constant > value) takes a const integer expression and widens it to i128 (at build > time only) before passing it as a const generic value to a new trait > function `FromConst::from_const`. The trait is implemented by NonZero, > Bounded, and Alignment and lets values of each be constructed from > constants without a verbose turbofish syntax. For example, > `const { NonZero::new(1).unwrap() }` can be written as `cv!(1)`. > > Suggested-by: Gary Guo > Signed-off-by: Eliot Courtney This doesn't work in const context, so I don't think this is a great strategy. I would want to use it for cases like this: drivers/android/binder/netlink.rs const BINDER_CMD_REPORT: u8 = kernel::uapi::BINDER_CMD_REPORT as u8; const BINDER_A_REPORT_ERROR: c_int = kernel::uapi::BINDER_A_REPORT_ERROR as c_int; const BINDER_A_REPORT_CONTEXT: c_int = kernel::uapi::BINDER_A_REPORT_CONTEXT as c_int; const BINDER_A_REPORT_FROM_PID: c_int = kernel::uapi::BINDER_A_REPORT_FROM_PID as c_int; const BINDER_A_REPORT_FROM_TID: c_int = kernel::uapi::BINDER_A_REPORT_FROM_TID as c_int; const BINDER_A_REPORT_TO_PID: c_int = kernel::uapi::BINDER_A_REPORT_TO_PID as c_int; const BINDER_A_REPORT_TO_TID: c_int = kernel::uapi::BINDER_A_REPORT_TO_TID as c_int; const BINDER_A_REPORT_IS_REPLY: c_int = kernel::uapi::BINDER_A_REPORT_IS_REPLY as c_int; const BINDER_A_REPORT_FLAGS: c_int = kernel::uapi::BINDER_A_REPORT_FLAGS as c_int; const BINDER_A_REPORT_CODE: c_int = kernel::uapi::BINDER_A_REPORT_CODE as c_int; const BINDER_A_REPORT_DATA_SIZE: c_int = kernel::uapi::BINDER_A_REPORT_DATA_SIZE as c_int; Alice