From nobody Sun Feb 8 16:31:25 2026 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.11]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CC29F355024; Thu, 13 Nov 2025 15:16:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.11 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763046976; cv=none; b=Sf/V8dGLWlwgEeapmvV0bNeXF3xWTkE1H5n9t8Wzv+PaUi40oLr42fTab252mNwlalpHjBcgncxh+c2pG6KnylF4ZmN6iRAXVbjBnouRQ/DVh+ew2j6u6UHSHYByvScZCRV64vYuNjUnJVPyS0LXU9IzaHhPDVA2NSdueQW3Yhk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763046976; c=relaxed/simple; bh=/cxJU6vGAsQflUr/+ZE9vbpP5RWmAFwZncC3phpHqKM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Y2v6ehSobBRJ3HUMXk8gDecB7W6pnT1bhnmMyftWQPgsBUXB2/7mGk9wMxlqJByr4PYIu2AmyYuNXsXGUjWvRNNDS35qLNR+0fIIJ6Il4xmoHUs8uprOXmGHEriSy+kCPXI8OcUaXPff1+dvumHkCJh31xXGJXLE5u6lQQ7ppsg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=TaCmLcBQ; arc=none smtp.client-ip=192.198.163.11 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="TaCmLcBQ" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1763046975; x=1794582975; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=/cxJU6vGAsQflUr/+ZE9vbpP5RWmAFwZncC3phpHqKM=; b=TaCmLcBQBh5PBiCKm6E/IljE1pxG4YivzorsYX8JKMpEwnWhjPUz3Wth 8hEM84N/JqSwInEg6R+N45yd+O0AZw8vv3/PZE82VBYrQUsUjNyVhjJV4 t4itenEWstT7qSVWOWaROAZIiax4toSgO5jZmUcTs+M72f7O8gxnrNSn/ wDaOcNXcBr7LgSMIqYTXR6Z6OsXaR/Bgb34PLXklQXGZPZyFLN3GAkvzY QDMbzuIYfRydONBMH8R2zrf9GntmKP+Mr0nPdgR5uvtwIf9q+MzYVPAEv ZNnV1OO3MvTID1mkXjo8keLx52sC4GGQeJ+4JvOPf8MWjJNOwrKJJIFUK g==; X-CSE-ConnectionGUID: 8BRvRzCiTrmNi2eyxscs8Q== X-CSE-MsgGUID: jegi2NZrTta1DOrBTe/NPw== X-IronPort-AV: E=McAfee;i="6800,10657,11612"; a="75740498" X-IronPort-AV: E=Sophos;i="6.19,302,1754982000"; d="scan'208";a="75740498" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by fmvoesa105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Nov 2025 07:16:11 -0800 X-CSE-ConnectionGUID: Jb5JgvfoRi6qyqGHFj6ZhA== X-CSE-MsgGUID: tb3HM3EYSHO8il86T39iKQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.19,302,1754982000"; d="scan'208";a="189792115" Received: from black.igk.intel.com ([10.91.253.5]) by fmviesa008.fm.intel.com with ESMTP; 13 Nov 2025 07:16:05 -0800 Received: by black.igk.intel.com (Postfix, from userid 1003) id B224697; Thu, 13 Nov 2025 16:16:04 +0100 (CET) From: Andy Shevchenko To: Andy Shevchenko , Bjorn Andersson , 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 , 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 v3 01/13] scatterlist: introduce sg_nents_for_dma() helper Date: Thu, 13 Nov 2025 16:12:57 +0100 Message-ID: <20251113151603.3031717-2-andriy.shevchenko@linux.intel.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20251113151603.3031717-1-andriy.shevchenko@linux.intel.com> References: <20251113151603.3031717-1-andriy.shevchenko@linux.intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 *s= gl, =20 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 l= en); + 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); =20 +/** + * sg_nents_for_dma - return the count of DMA-capable entries in scatterli= st + * @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 l= en) +{ + struct scatterlist *sg; + int i, nents =3D 0; + + for_each_sg(sgl, sg, sglen, i) + nents +=3D 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 --=20 2.50.1