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 A6CB2CFD313 for ; Mon, 24 Nov 2025 12:12:19 +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=vkErowuKqNkd+wim7rdnfISv/3 puOgx+791679/OVSshIrI7BDLrwc6QN4BtS/zcUlkZXsM+5jATZZN136ICRisoxGym4owbUk6nhnz Khe9CwOk6YWQrJN7aMeaUAOjpNT/mvKDVJiYnQb6tV5RiKarszorBZmKIH967I3b4tw6oXAAmiUWS bU1Xg2cC6cBRc155+aAV9qcmqMYqkNaACgOirsS8z1HWWy7PrqSgnDrHZxV2h7QSvWy+tOCIhQULH H/2ZfPsqSlMiGnAQpEYPsmDvuDol2djnX5UYHknG4XpPsug+/QuBELxrMz5piMfhnd+O9eF3+fkA3 dc7k/bJg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vNVQU-0000000BcQZ-11wV; Mon, 24 Nov 2025 12:12:14 +0000 Received: from mgamail.intel.com ([192.198.163.7]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vNVQQ-0000000BcP4-1EEZ; Mon, 24 Nov 2025 12:12:11 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1763986330; x=1795522330; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=/cxJU6vGAsQflUr/+ZE9vbpP5RWmAFwZncC3phpHqKM=; b=jMIquwsJ4zjNZw6+PufC4oOiI0DdMin6gvsQmtSnqDOjhiqgc7g09bvo MW6HlevxH78/Ty2e5MfqE0Ef9EsysfcjL7XQKxDU+epIMDl5fdN1oD7br f7zRj4dQvr3URXFipvCww+XGgMqYuJt/iqBFk6BuhoaVC2E3vuoNNeVmP +uSRHESyTje980Yu7MZG/+6Sxv2lSGxhQ9KpDiytFwz8ayFMTwe4ttT3Z 2BT32Cqk10VEMSXQfYCXyQHjh1d6Ws6JHsqyADom8uEboZTRuH0b0Lffe EWg4T1MzItsruSL2wN6JRO0uhjPxU0RB45yUTtzn/k8PP9brsUdzeMAf3 A==; X-CSE-ConnectionGUID: sMiMXSdIQuOttPglGaSsLA== X-CSE-MsgGUID: 5O2WpllHRpKEi0rla4RjjA== X-IronPort-AV: E=McAfee;i="6800,10657,11622"; a="91467911" X-IronPort-AV: E=Sophos;i="6.20,222,1758610800"; d="scan'208";a="91467911" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by fmvoesa101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Nov 2025 04:12:09 -0800 X-CSE-ConnectionGUID: fh/9F8B6QSyvv2FZin4FtQ== X-CSE-MsgGUID: v9ZK9M8yQI6oey+Xgb50lQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.20,222,1758610800"; d="scan'208";a="192559536" Received: from black.igk.intel.com ([10.91.253.5]) by fmviesa008.fm.intel.com with ESMTP; 24 Nov 2025 04:12:04 -0800 Received: by black.igk.intel.com (Postfix, from userid 1003) id 4975DA1; Mon, 24 Nov 2025 13:12:03 +0100 (CET) From: Andy Shevchenko To: Bjorn Andersson , Andy Shevchenko , Stefan Wahren , Vinod Koul , 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 , Ray Jui , Scott Branden , Broadcom internal kernel review list , Lars-Peter Clausen , Eugeniy Paltsev , Daniel Mack , Haojian Zhuang , Robert Jarzmik , Lizhi Hou , Brian Xu , Raj Kumar Rampelli , Michal Simek , Andrew Morton Subject: [PATCH v4 01/13] scatterlist: introduce sg_nents_for_dma() helper Date: Mon, 24 Nov 2025 13:09:19 +0100 Message-ID: <20251124121202.424072-2-andriy.shevchenko@linux.intel.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20251124121202.424072-1-andriy.shevchenko@linux.intel.com> References: <20251124121202.424072-1-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-20251124_041210_368043_EE425D62 X-CRM114-Status: GOOD ( 12.95 ) 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