From 80c70bfb95cdbe0c644070f4ca4754a60f0a4830 Mon Sep 17 00:00:00 2001 From: Andy Shevchenko Date: Thu, 8 Jan 2026 11:50:12 +0100 Subject: scatterlist: introduce sg_nents_for_dma() helper 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 Link: https://patch.msgid.link/20260108105619.3513561-2-andriy.shevchenko@linux.intel.com Signed-off-by: Vinod Koul --- lib/scatterlist.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) (limited to 'lib') 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 -- cgit v1.2.3