From nobody Sat Feb 7 09:59:23 2026 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.13]) (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 C7543350A26; Thu, 8 Jan 2026 10:56:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.13 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767869807; cv=none; b=hE9rPfxFNSaKC6OU8ZGgZ8aaI9MmAAO5gxIJGIaXmHteyedeH7zTagWK92RUTOYKSXsWf66BUF3+5h3Up+VlAS77CUTqvW5P78pinBh+h+ZShC8avu17n5Y0IAxRqG7odgVz9v0dWIx9uLasOySNZTDFvmc591MBxMYAngtLFb4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767869807; c=relaxed/simple; bh=/cxJU6vGAsQflUr/+ZE9vbpP5RWmAFwZncC3phpHqKM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=EDFmXpkP+QPVJ4GQYZuavW6o6bsvuDuoLZRuuw8vqwbmDBJcvm+/l8LqHp0N/yAdOpgoPO2g25agIuZW9aepcFF5THu9lOYMvLGEsvxk06KXWP6+moE8+mKL3OTtS0SQdxvxA3BQlJ+rblrR4t36iZKskzcvsTj+y3RmeVObG3s= 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=jmehJVc+; arc=none smtp.client-ip=198.175.65.13 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="jmehJVc+" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1767869799; x=1799405799; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=/cxJU6vGAsQflUr/+ZE9vbpP5RWmAFwZncC3phpHqKM=; b=jmehJVc+L7xtjDVCRabq/wqHHUkjgXX36nUgCikKuKg7FPqIFYvpdZNK wH3OIU6SIBCRAi8H/S8rHQZ7ElhuRpJbpiMZe6XmXVpDAsNsNER0WrGR/ QdoyJowHsXXpVRtLqRdSzME1L4xs/Naj1cirB/c5Om8XvxTBTPmlokuC5 K49fed19bZJayVIZiCQyoZff2hgyCgU4KSQ7EUrMJoeCtTW7MVfAgt/As pDvh+PLhWXIoXTsrt/O/YYb3IzxTlUFBcDWzDY93UxQnmxkHmGTJiTC7D X7tdeOq6y5ModNQIoyDGnWeQnlEPh4QW+xkcsOMNa4+t84OHSVcrkgIQZ w==; X-CSE-ConnectionGUID: 5n5yLmH0TvK63o+k6gJXMw== X-CSE-MsgGUID: QwM/4aDNS+KPcKjKufkRRA== X-IronPort-AV: E=McAfee;i="6800,10657,11664"; a="80354547" X-IronPort-AV: E=Sophos;i="6.21,210,1763452800"; d="scan'208";a="80354547" 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> 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