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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 65F09C28CF5 for ; Wed, 26 Jan 2022 15:20:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=Y1ousi5oSZw9qrwb2HrftGIJOHykphUL0aBRFsjOI2M=; b=PyVW4/BX1pSf7Z b55gZlp8faW8g1I950dpKGjlPUZwynLT4wPFoI0imLN3NAFhks+WrnDzAToNcHoOqgcJv/GZ11cPc 4Dep0Khbjc2aPWgaOsAT9L3P4cavot3RPlGVoennUOsP2ap9usmG4bsSiwUqytfxHZo9fHtPy//9d PZHzo1qJ+du/CyFR9ZsxWTitEB60+GlC3lRHCqKIhrKhfVYUeQTLanspA/ZCNT6Ls6oI8OJYxvpvt Jf+IxrJqdkaDS99IIXpfQF6wAzZK+myoPiXtF9IRSTpz1YTm400wLXz2K/fYmdHAcccUyevEpzhTC QtIwLc4q9jOOiDq1ET0w==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nCk4A-00CDm3-63; Wed, 26 Jan 2022 15:18:35 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nCjpN-00C6fL-Pl for linux-arm-kernel@lists.infradead.org; Wed, 26 Jan 2022 15:03:20 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 09C121FB; Wed, 26 Jan 2022 07:03:16 -0800 (PST) Received: from donnerap.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 093103F793; Wed, 26 Jan 2022 07:03:14 -0800 (PST) Date: Wed, 26 Jan 2022 15:03:12 +0000 From: Andre Przywara To: Mark Rutland Cc: linux-arm-kernel@lists.infradead.org, broonie@kernel.org, jaxson.han@arm.com, robin.murphy@arm.com, vladimir.murzin@arm.com, wei.chen@arm.com Subject: Re: [bootwrapper PATCH v3 04/15] Add bit-field macros Message-ID: <20220126150312.56b6f536@donnerap.cambridge.arm.com> In-Reply-To: <20220125150057.3936090-5-mark.rutland@arm.com> References: <20220125150057.3936090-1-mark.rutland@arm.com> <20220125150057.3936090-5-mark.rutland@arm.com> Organization: ARM X-Mailer: Claws Mail 3.17.5 (GTK+ 2.24.32; aarch64-unknown-linux-gnu) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220126_070318_022423_2BC1BE6A X-CRM114-Status: GOOD ( 23.85 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, 25 Jan 2022 15:00:46 +0000 Mark Rutland wrote: > Arm architectural documentation typically defines bit-fields as > `[msb,lsb]` and single-bit fields as `[bit]`. For clarity it would be > helpful if we could define fields in the same way. > > Add helpers so that we can do so, along with helper to extract/insert > bit-field values. > > There should be no functional change as a result of this patch. > > Signed-off-by: Mark Rutland I extracted the code and checked the examples, see below. > --- > include/bits.h | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 66 insertions(+) > create mode 100644 include/bits.h > > diff --git a/include/bits.h b/include/bits.h > new file mode 100644 > index 0000000..5f0ad8f > --- /dev/null > +++ b/include/bits.h > @@ -0,0 +1,66 @@ > +/* > + * include/bits.h - helpers for bit-field definitions. > + * > + * Copyright (C) 2021 ARM Limited. All rights reserved. > + * > + * Use of this source code is governed by a BSD-style license that can be > + * found in the LICENSE.txt file. > + */ > +#ifndef __BITS_H > +#define __BITS_H > + > +#ifdef __ASSEMBLY__ > +#define UL(x) x > +#define ULL(x) x > +#else > +#define UL(x) x##UL > +#define ULL(x) x##ULL > +#endif > + > +/* > + * Define a contiguous mask of bits with `msb` as the most significant bit and > + * `lsb` as the least significant bit. The `msb` value must be greater than or > + * equal to `lsb`. > + * > + * For example: > + * - BITS(63, 63) is 0x8000000000000000 > + * - BITS(63, 0) is 0xFFFFFFFFFFFFFFFF > + * - BITS(0, 0) is 0x0000000000000001 > + * - BITS(49, 17) is 0x0001FFFFFFFE0000 This should be 0x0003fffffffe0000, in real life and with the below implementation. So just a comment fix. The rest of the examples checked out, so with that fixed: Reviewed-by: Andre Przywara Cheers, Andre > + */ > +#define BITS(msb, lsb) \ > + ((~ULL(0) >> (63 - msb)) & (~ULL(0) << lsb)) > + > +/* > + * Define a mask of a single set bit `b`. > + * > + * For example: > + * - BIT(63) is 0x8000000000000000 > + * - BIT(0) is 0x0000000000000001 > + * - BIT(32) is 0x0000000100000000 > + */ > +#define BIT(b) BITS(b, b) > + > +/* > + * Find the least significant set bit in the contiguous set of bits in `mask`. > + * > + * For example: > + * - BITS_LSB(0x0000000000000001) is 0 > + * - BITS_LSB(0x000000000000ff00) is 8 > + * - BITS_LSB(0x8000000000000000) is 63 > + */ > +#define BITS_LSB(mask) (__builtin_ffsll(mask) - 1) > + > +/* > + * Extract a bit-field out of `val` described by the contiguous set of bits in > + * `mask`. > + * > + * For example: > + * - BITS_EXTRACT(0xABCD, BITS(15, 12)) is 0xA > + * - BITS_EXTRACT(0xABCD, BITS(11, 8)) is 0xB > + * - BITS_EXTRACT(0xABCD, BIT(7)) is 0x1 > + */ > +#define BITS_EXTRACT(val, mask) \ > + (((val) & (mask)) >> BITS_LSB(mask)) > + > +#endif _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel