From patchwork Tue Mar 25 15:59:57 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vincent Mailhol X-Patchwork-Id: 14029199 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 5F5E3C3600B for ; Tue, 25 Mar 2025 16:06:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Reply-To:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:Cc:To:In-Reply-To: References:Message-Id:Content-Transfer-Encoding:Content-Type:MIME-Version: Subject:Date:From:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=g44DiPntgxgai8nMrZBqC2mFlTLQIzQV5yIGLqcK/Sc=; b=s8uKRAmbQ8dS3FS1P9ZWJgoKsj cQo8/B0hKWMK2FXHk31M+SVz/p1ZPNsdFVoa11YjLsRkM2R527jWHWZv01jTZNWa3wFxDZGbVqLDJ Az9rb2xvMz22H6WfZ6yQCgm+TUPaWFH7XcBBNSwJIAw/heY5Gg9RParUMhB8dpSjXYFDpwkiHJnI/ kHqCj+hs32sn/E0clQl2+DkFMMs1sD/g918JCimGLBbteFDBqR9L4TxSm4kdAblpaIV7fw488aFD3 JrLdqwh8lMOh89D1m+mDxLEFpNaRlTzqqc4LTvgQtvZ7Q38kl4MkJgiABl8hHmZYt2SVF8rKaBQHd UhmsUZ+w==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.1 #2 (Red Hat Linux)) id 1tx6n0-00000006QhT-0foQ; Tue, 25 Mar 2025 16:06:06 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.98.1 #2 (Red Hat Linux)) id 1tx6ht-00000006PeB-3Uca for linux-arm-kernel@lists.infradead.org; Tue, 25 Mar 2025 16:00:49 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id ED87761158; Tue, 25 Mar 2025 16:00:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPS id CE138C4CEEA; Tue, 25 Mar 2025 16:00:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1742918448; bh=FWMREnd5iDlVSh5Gzp0i6UEx3AjyWEabj/dQba8l/fw=; h=From:Date:Subject:References:In-Reply-To:To:Cc:Reply-To:From; b=d2BCH6k8jCjMfB0ksgtoz6h9i7DZTMmcxkudiYS/VpSNf2CcdRdEvNsMnHbKX6SFq sClPwVdBqkyFq0DxxYV65mjK4piHj1L7NfsbLMjSZ3A7SwrC92/8SLVjoXN6atlOQL +t+XW2hdvoZmGYdVxxaveWTcitefwDtIXT3j9YlOFmJgAhh9KNjAerE/ula8hZozmI 4fGqJh7dO2d6/tpgjN9LvzaN+fWGCooBTCpXwnCMEVrGvxIdU0j8PlyX+l+14uDlVE 30B8tu1WC108EUQ/sNu/Dy46TGvUkPSqZ8Pk3ICxjIlp3Z1Y9lSDVIZP2e8kG9Ivni ia0RmJY3TLDQQ== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id C095DC3600B; Tue, 25 Mar 2025 16:00:48 +0000 (UTC) Date: Wed, 26 Mar 2025 00:59:57 +0900 Subject: [PATCH v8 2/6] bits: introduce fixed-type GENMASK_U*() MIME-Version: 1.0 Message-Id: <20250326-fixed-type-genmasks-v8-2-24afed16ca00@wanadoo.fr> References: <20250326-fixed-type-genmasks-v8-0-24afed16ca00@wanadoo.fr> In-Reply-To: <20250326-fixed-type-genmasks-v8-0-24afed16ca00@wanadoo.fr> To: Yury Norov , Lucas De Marchi , Rasmus Villemoes , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Simona Vetter , Andrew Morton Cc: linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, Andi Shyti , David Laight , Andy Shevchenko , Catalin Marinas , Anshuman Khandual , linux-arm-kernel@lists.infradead.org, Jani Nikula , Vincent Mailhol X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=6477; i=mailhol.vincent@wanadoo.fr; h=from:subject:message-id; bh=lcd0sGudcgWuhmZH+0WWzv0DQlUpekaFcQVtmkcurBs=; b=owGbwMvMwCV2McXO4Xp97WbG02pJDOmPLiuVfl9Vwe30Wjf/qqRU0O2a5fe5tkWeVV/1MvBOd 8v6CovfHaUsDGJcDLJiiizLyjm5FToKvcMO/bWEmcPKBDKEgYtTACbScpCRYVZX7pcyzcNR+wMO vQjM7zWfP1Xpk43BgdbmpgUlDHmf2Bj+RyYf4HrYX7a+ncuO4X5mkIbpdp//nrxi0181q21nkI/ hAgA= X-Developer-Key: i=mailhol.vincent@wanadoo.fr; a=openpgp; fpr=ED8F700574E67F20E574E8E2AB5FEB886DBB99C2 X-Endpoint-Received: by B4 Relay for mailhol.vincent@wanadoo.fr/default with auth_id=291 X-Original-From: Vincent Mailhol 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: , Reply-To: mailhol.vincent@wanadoo.fr Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Vincent Mailhol From: Vincent Mailhol Add GENMASK_TYPE() which generalizes __GENMASK() to support different types, and implement fixed-types versions of GENMASK() based on it. The fixed-type version allows more strict checks to the min/max values accepted, which is useful for defining registers like implemented by i915 and xe drivers with their REG_GENMASK*() macros. The strict checks rely on shift-count-overflow compiler check to fail the build if a number outside of the range allowed is passed. Example: #define FOO_MASK GENMASK_U32(33, 4) will generate a warning like: include/linux/bits.h:51:27: error: right shift count >= width of type [-Werror=shift-count-overflow] 51 | type_max(t) >> (BITS_PER_TYPE(t) - 1 - (h))))) | ^~ The result is casted to the corresponding fixed width type. For example, GENMASK_U8() returns an u8. Note that because of the C promotion rules, GENMASK_U8() and GENMASK_U16() will immediately be promoted to int if used in an expression. Regardless, the main goal is not to get the correct type, but rather to enforce more checks at compile time. While GENMASK_TYPE() is crafted to cover all variants, including the already existing GENMASK(), GENMASK_ULL() and GENMASK_U128(), for the moment, only use it for the newly introduced GENMASK_U*(). The consolidation will be done in a separate change. Co-developed-by: Yury Norov Signed-off-by: Yury Norov Signed-off-by: Lucas De Marchi Acked-by: Jani Nikula Signed-off-by: Vincent Mailhol Reviewed-by: Andy Shevchenko --- Changelog: v7 -> v8: - s/shift-count-overflow/-Wshift-count-overflow/g - add an explanation about the return value cast in the patch description. v6 -> v7: - Fix grammar in comment: 'GENMASK_U*() depends' -> 'GENMASK_U*() depend'. - Fix typo in comment: 'Nethertheless' -> 'Nevertheless' - Do an artificial early line wrap in comment so that the next patch only has a one line diff change. - Re-wrap the comments to the 80th column. - The patch changed a lot since Yury first version: put myself as main author and Yury as Co-developer. - Add a new paragraph to the patch description to explain that consolidation will be done later. v5 -> v6: - No changes. v4 -> v5: - Rename GENMASK_t() to GENMASK_TYPE(). - Fix typo in patch description. - Use tab indentations instead of single space to separate the macro name from its body. - s/__GENMASK_U*()/GENMASK_U*()/g in the comment. - Add a tag to credit myself as Co-developer. Keep Yury as the main author. - Modify GENMASK_TYPE() to match the changes made to __GENMASK() in: https://github.com/norov/linux/commit/1e7933a575ed - Replace (t)~_ULL(0) with type_max(t). This is OK because GENMASK_TYPE() is not available in asm. - linux/const.h and asm/bitsperlong.h are not used anymore. Remove them. - Apply GENMASK_TYPE() to GENMASK_U128(). - Remove the unsigned int cast for the U8 and U16 variants. Cast to the target type instead. Do that cast directly in GENMASK_TYPE(). v3 -> v4: - The v3 is one year old. Meanwhile people started using __GENMASK() directly. So instead of generalizing __GENMASK() to support different types, add a new GENMASK_t(). - replace ~0ULL by ~_ULL(0). Otherwise, GENMASK_t() would fail in asm code. - Make GENMASK_U8() and GENMASK_U16() return an unsigned int. In v3, due to the integer promotion rules, these were returning a signed integer. By casting these to unsigned int, at least the signedness is kept. --- include/linux/bitops.h | 1 - include/linux/bits.h | 30 ++++++++++++++++++++++++++++++ 2 files changed, 30 insertions(+), 1 deletion(-) diff --git a/include/linux/bitops.h b/include/linux/bitops.h index c1cb53cf2f0f8662ed3e324578f74330e63f935d..9be2d50da09a417966b3d11c84092bb2f4cd0bef 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -8,7 +8,6 @@ #include -#define BITS_PER_TYPE(type) (sizeof(type) * BITS_PER_BYTE) #define BITS_TO_LONGS(nr) __KERNEL_DIV_ROUND_UP(nr, BITS_PER_TYPE(long)) #define BITS_TO_U64(nr) __KERNEL_DIV_ROUND_UP(nr, BITS_PER_TYPE(u64)) #define BITS_TO_U32(nr) __KERNEL_DIV_ROUND_UP(nr, BITS_PER_TYPE(u32)) diff --git a/include/linux/bits.h b/include/linux/bits.h index e1e5177691406919ba4f5bbc875bd230414fd117..9718c5ae5fc356e66958cf48667bb1edda4f9673 100644 --- a/include/linux/bits.h +++ b/include/linux/bits.h @@ -12,6 +12,7 @@ #define BIT_ULL_MASK(nr) (ULL(1) << ((nr) % BITS_PER_LONG_LONG)) #define BIT_ULL_WORD(nr) ((nr) / BITS_PER_LONG_LONG) #define BITS_PER_BYTE 8 +#define BITS_PER_TYPE(type) (sizeof(type) * BITS_PER_BYTE) /* * Create a contiguous bitmask starting at bit position @l and ending at @@ -20,11 +21,40 @@ */ #if !defined(__ASSEMBLY__) +/* + * Missing asm support + * + * GENMASK_U*() depend on BITS_PER_TYPE() which relies on sizeof(), + * something not available in asm. Nevertheless, fixed width integers is a C + * concept. Assembly code can rely on the long and long long versions instead. + */ + #include #include +#include #define GENMASK_INPUT_CHECK(h, l) BUILD_BUG_ON_ZERO(const_true((l) > (h))) +/* + * Generate a mask for the specified type @t. Additional checks are made to + * guarantee the value returned fits in that type, relying on + * -Wshift-count-overflow compiler check to detect incompatible arguments. + * For example, all these create build errors or warnings: + * + * - GENMASK(15, 20): wrong argument order + * - GENMASK(72, 15): doesn't fit unsigned long + * - GENMASK_U32(33, 15): doesn't fit in a u32 + */ +#define GENMASK_TYPE(t, h, l) \ + ((t)(GENMASK_INPUT_CHECK(h, l) + \ + (type_max(t) << (l) & \ + type_max(t) >> (BITS_PER_TYPE(t) - 1 - (h))))) + +#define GENMASK_U8(h, l) GENMASK_TYPE(u8, h, l) +#define GENMASK_U16(h, l) GENMASK_TYPE(u16, h, l) +#define GENMASK_U32(h, l) GENMASK_TYPE(u32, h, l) +#define GENMASK_U64(h, l) GENMASK_TYPE(u64, h, l) + #else /* defined(__ASSEMBLY__) */ /*