From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 C69C7157493; Wed, 16 Jul 2025 09:15:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752657344; cv=none; b=cBTYHghUDzjW1qurX0lENqDzuDSRfoRHgCLbcJCur8OXYuEtYHzw5zzSWhuiXQSirOC47ILRh/sfJJ4KqcAGD+tl0wb/WLUz5fGPp55+R/waYTWhQ3DYacgKzAscB93JtSFnMWbLCh5dqWWSI06ObZmTUxlCHJAyBquaMuXpi+k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752657344; c=relaxed/simple; bh=ONPNBASW2TlNyQh0oBZI7v9HNhfprjI2hTF1LVI4XTQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=DnzLXLG2yUrZU3TkPlg24oHwwx4kfuf9BQHKPb89INkPxazbJs2YtdPMlPYWPx1g5ZCXffEYxyIVjc/XEboYWpamhNrRQgl+YVzvJC1O97UElVi4UmV7NHaptJPKYSd9f1onNc9O0koGuIVW1ADr4ixZ8mrVnIqyPu2QmposGJE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=nnUBjipM; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="nnUBjipM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C4243C4CEF1; Wed, 16 Jul 2025 09:15:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1752657342; bh=ONPNBASW2TlNyQh0oBZI7v9HNhfprjI2hTF1LVI4XTQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=nnUBjipMfPB2BJS84RlGSNZsB9Ay7VhRRQ32xD2SjO7iD2mOCg4UVNkCWF60AO6tK P9PWMcw2UA1/H9AlpuU++Y3qv0I4DzrpkVQgheexwOv9KjL6KHd5OAdeuFzX4tHkbH JMfcp2EGdO4c44eIJoMmu3ucEsk0nCqK14gtRdVg= Date: Wed, 16 Jul 2025 11:15:39 +0200 From: Greg KH To: Danilo Krummrich Cc: abdiel.janulgue@gmail.com, daniel.almeida@collabora.com, robin.murphy@arm.com, a.hindborg@kernel.org, ojeda@kernel.org, alex.gaynor@gmail.com, boqun.feng@gmail.com, gary@garyguo.net, bjorn3_gh@protonmail.com, lossin@kernel.org, aliceryhl@google.com, tmgross@umich.edu, bhelgaas@google.com, kwilczynski@kernel.org, rafael@kernel.org, rust-for-linux@vger.kernel.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/5] rust: dma: add DMA addressing capabilities Message-ID: <2025071627-outlet-slacker-9382@gregkh> References: <20250710194556.62605-1-dakr@kernel.org> <20250710194556.62605-3-dakr@kernel.org> Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250710194556.62605-3-dakr@kernel.org> On Thu, Jul 10, 2025 at 09:45:44PM +0200, Danilo Krummrich wrote: > +/// Returns a bitmask with the lowest `n` bits set to `1`. > +/// > +/// For `n` in `0..=64`, returns a mask with the lowest `n` bits set. > +/// For `n > 64`, returns `u64::MAX` (all bits set). > +/// > +/// # Examples > +/// > +/// ``` > +/// use kernel::dma::dma_bit_mask; > +/// > +/// assert_eq!(dma_bit_mask(0), 0); > +/// assert_eq!(dma_bit_mask(1), 0b1); > +/// assert_eq!(dma_bit_mask(64), u64::MAX); > +/// assert_eq!(dma_bit_mask(100), u64::MAX); // Saturates at all bits set. > +/// ``` > +pub const fn dma_bit_mask(n: usize) -> u64 { > + match n { > + 0 => 0, > + 1..=64 => u64::MAX >> (64 - n), > + _ => u64::MAX, > + } > +} This is just the C macro DMA_BIT_MASK(), right? If so, can that be said here somewhere? Or, how about turning DMA_BIT_MASK() into an inline function which could then be just called by the rust code directly instead? Just a minor thing, but it stood out to me here. thanks, greg k-h