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 79CCED185D6 for ; Thu, 8 Jan 2026 10:56:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=FsM1ztKXi3y+tX16b2iiEH9QqHspOPTUgYvJo8a7BhI=; b=h9P1/OHxVSevLuRJPTuoinEcga Excdrdq0Tzjj8MyN0uU3vJheNSZQbvrE1pjDqFMWyTn34uSxqv0SXNCnUWL8NZOgJM1ai1tWsbsIj v5bZ0fYmJFImxpuWuVneEjOjNFNoodMr7HjBhK534xSR57a2G1htJ6VCOCCesYOc4KSWxoeqJTuS+ nvskW/zehI6y0XqQ9m+QZHO5K4TJrsoatlyFYhoyz4zcIeGurSwDEM/18oPWb+YtUWl6AshjYBnoz wg7s441IcpX/iyaXcTyvcv7E59eWLSgQIndIsL7sHlJ4RBX+NWwTrK1rv0pySJTWKw34QJ+vTz3Zi BC8GJycg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vdngs-0000000GkJM-49Hb; Thu, 08 Jan 2026 10:56:30 +0000 Received: from mgamail.intel.com ([198.175.65.13]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vdngq-0000000GkHx-2ccI; Thu, 08 Jan 2026 10:56:29 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1767869789; x=1799405789; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=/cxJU6vGAsQflUr/+ZE9vbpP5RWmAFwZncC3phpHqKM=; b=EIRvb4qL2bIrkxW6RMOoQ+nfY1vpeLlAqv/hWb5rX2K4bRq0YP/lLXlE pp63yJCF1j4xAXRPqejBXQll/7WmSqJyrwwRRZ87AzKmmZijKWe9lSf80 6qp5AvI/uVr1IhKdKhvzoafjGXL3dTEhGCx4kb09hWHdP7jUduCTPMiV4 dttXr+AyjYTWZxdXLJwXm5TfGcc6oAl+7VYWBSh5LjMQfrGPY6G2jj2xs sKDWoMMHOZ27ueqnXqhwEesf7kzERbxXEIw4AMNZbFJ1RLfK4PZpUFPlu OG7DG2mis5lrsEqoouJxRtAgXws4ZmH6ibg58GWkfPwQ5taKXu6Su5Dy0 w==; X-CSE-ConnectionGUID: C+w+BIn6RoSO9n8uFLyP4w== X-CSE-MsgGUID: tEGsZMs0QZSZazUZVQWp9Q== X-IronPort-AV: E=McAfee;i="6800,10657,11664"; a="80354545" X-IronPort-AV: E=Sophos;i="6.21,210,1763452800"; d="scan'208";a="80354545" Received: from fmviesa009.fm.intel.com ([10.60.135.149]) by orvoesa105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Jan 2026 02:56:27 -0800 X-CSE-ConnectionGUID: J4Qr4JKcTiKmKvrG3ivuJg== X-CSE-MsgGUID: wvoTnZnrRaiKzhZI7CYxBg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.21,210,1763452800"; d="scan'208";a="203615536" Received: from black.igk.intel.com ([10.91.253.5]) by fmviesa009.fm.intel.com with ESMTP; 08 Jan 2026 02:56:21 -0800 Received: by black.igk.intel.com (Postfix, from userid 1003) id 4179499; Thu, 08 Jan 2026 11:56:20 +0100 (CET) From: Andy Shevchenko To: Bjorn Andersson , Andy Shevchenko , =?UTF-8?q?Nuno=20S=C3=A1?= , Vinod Koul , Bartosz Golaszewski , Thomas Andreatta , Caleb Sander Mateos , dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org Cc: Olivier Dautricourt , Stefan Roese , Florian Fainelli , Broadcom internal kernel review list , Ray Jui , Scott Branden , Lars-Peter Clausen , Eugeniy Paltsev , Daniel Mack , Haojian Zhuang , Robert Jarzmik , Lizhi Hou , Brian Xu , Raj Kumar Rampelli , Michal Simek , Andrew Morton Subject: [PATCH v5 01/13] scatterlist: introduce sg_nents_for_dma() helper Date: Thu, 8 Jan 2026 11:50:12 +0100 Message-ID: <20260108105619.3513561-2-andriy.shevchenko@linux.intel.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260108105619.3513561-1-andriy.shevchenko@linux.intel.com> References: <20260108105619.3513561-1-andriy.shevchenko@linux.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260108_025628_707417_4FB816F9 X-CRM114-Status: GOOD ( 12.55 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Sometimes the user needs to split each entry on the mapped scatter list due to DMA length constrains. This helper returns a number of entities assuming that each of them is not bigger than supplied maximum length. Reviewed-by: Bjorn Andersson Signed-off-by: Andy Shevchenko --- include/linux/scatterlist.h | 2 ++ lib/scatterlist.c | 26 ++++++++++++++++++++++++++ 2 files changed, 28 insertions(+) diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index 29f6ceb98d74..6de1a2434299 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -441,6 +441,8 @@ static inline void sg_init_marker(struct scatterlist *sgl, int sg_nents(struct scatterlist *sg); int sg_nents_for_len(struct scatterlist *sg, u64 len); +int sg_nents_for_dma(struct scatterlist *sgl, unsigned int sglen, size_t len); + struct scatterlist *sg_last(struct scatterlist *s, unsigned int); void sg_init_table(struct scatterlist *, unsigned int); void sg_init_one(struct scatterlist *, const void *, unsigned int); diff --git a/lib/scatterlist.c b/lib/scatterlist.c index 4af1c8b0775a..21bc9c1f7c06 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -64,6 +64,32 @@ int sg_nents_for_len(struct scatterlist *sg, u64 len) } EXPORT_SYMBOL(sg_nents_for_len); +/** + * sg_nents_for_dma - return the count of DMA-capable entries in scatterlist + * @sgl: The scatterlist + * @sglen: The current number of entries + * @len: The maximum length of DMA-capable block + * + * Description: + * Determines the number of entries in @sgl which would be permitted in + * DMA-capable transfer if list had been split accordingly, taking into + * account chaining as well. + * + * Returns: + * the number of sgl entries needed + * + **/ +int sg_nents_for_dma(struct scatterlist *sgl, unsigned int sglen, size_t len) +{ + struct scatterlist *sg; + int i, nents = 0; + + for_each_sg(sgl, sg, sglen, i) + nents += DIV_ROUND_UP(sg_dma_len(sg), len); + return nents; +} +EXPORT_SYMBOL(sg_nents_for_dma); + /** * sg_last - return the last scatterlist entry in a list * @sgl: First entry in the scatterlist -- 2.50.1