From patchwork Sat Mar 22 09:23:12 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vincent Mailhol X-Patchwork-Id: 14026177 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 D1765C36002 for ; Sat, 22 Mar 2025 09:24:29 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 021A610E2C3; Sat, 22 Mar 2025 09:24:25 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="rV8du4YS"; dkim-atps=neutral Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by gabe.freedesktop.org (Postfix) with ESMTPS id 601E110E2C2; Sat, 22 Mar 2025 09:24:21 +0000 (UTC) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id E076143B36; Sat, 22 Mar 2025 09:24:11 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPS id 19F4BC4CEE9; Sat, 22 Mar 2025 09:24:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1742635452; bh=thQWTrjIZZYS/UhShjmRT3f+9I5W5RZ+OaG+tV1AiMI=; h=From:Date:Subject:References:In-Reply-To:To:Cc:Reply-To:From; b=rV8du4YSr51bvYGhxMqWfPC0ybsGbG/R5cPK/10kCjAdtOyO1kg10cI7UrIra7CNj ZxJd72Ae1sUwdUbKLwiltwPPIEv54/+DiGjbTjNB2pFyQaPgEMHa6zCJVgnZPzUcHC U1Bf1+B8XxIHMArrWv+W+fYVoLNlrhzaXivc5KJ6u651xo3WRJpZGU1d+AeiWm1HEA JAYYQO6t4kWr3+RpNnHvXZ9zoXvTRiyrFr+TRCxxUTnKuXY4NYHzkuRgJeK3mxVgyC DuB1tRAxfbmCuQRf9vqnanyMhyppyYy9py46Cnh/H4C2nCdkv/zrvbYS/Qq2kpY9eZ MKN0HOna6c7eQ== 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 098DCC36002; Sat, 22 Mar 2025 09:24:12 +0000 (UTC) Date: Sat, 22 Mar 2025 18:23:12 +0900 Subject: [PATCH v7 1/5] bits: introduce fixed-type GENMASK_U*() MIME-Version: 1.0 Message-Id: <20250322-fixed-type-genmasks-v7-1-da380ff1c5b9@wanadoo.fr> References: <20250322-fixed-type-genmasks-v7-0-da380ff1c5b9@wanadoo.fr> In-Reply-To: <20250322-fixed-type-genmasks-v7-0-da380ff1c5b9@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 , Jani Nikula , Vincent Mailhol X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=6346; i=mailhol.vincent@wanadoo.fr; h=from:subject:message-id; bh=H6EVGTMFrJBD0BwQz7pCCSuZTsJFcePLWSVIjCdGvXE=; b=owGbwMvMwCV2McXO4Xp97WbG02pJDOn3Gtde2+1v1nxEf4F+zeI94jPc4968UvMWzmgI477QZ H2rUM2po5SFQYyLQVZMkWVZOSe3Qkehd9ihv5Ywc1iZQIYwcHEKwERUbzIy7O3kMXO/Yb1M5cre TWe6jk/n/sguLd62K8pt+XdnY583cQz/jPrUQiue7ORie8KhFKY3q2ZCaPrdVx+W/VrrXbu6nN2 BDwA= 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: 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: , Reply-To: mailhol.vincent@wanadoo.fr Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" 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))))) | ^~ 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 --- Changelog: 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 | 39 +++++++++++++++++++++++++++++++++++++-- 2 files changed, 37 insertions(+), 3 deletions(-) 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 14fd0ca9a6cd17339dd2f69e449558312a8a001b..beb3ee2f1bc74a9346dd72eb06c722a9bc536051 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 @@ -19,16 +20,50 @@ * GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000. */ #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))) -#else + +/* + * Generate a mask for the specified type @t. Additional checks are made to + * guarantee the value returned fits in that type, relying on + * shift-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__) */ + /* * BUILD_BUG_ON_ZERO is not available in h files included from asm files, * disable the input check if that is the case. */ #define GENMASK_INPUT_CHECK(h, l) 0 -#endif + +#endif /* !defined(__ASSEMBLY__) */ #define GENMASK(h, l) \ (GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l))