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| author | Andy Shevchenko <andriy.shevchenko@linux.intel.com> | 2026-01-08 13:50:12 +0300 |
|---|---|---|
| committer | Vinod Koul <vkoul@kernel.org> | 2026-01-09 06:06:00 +0300 |
| commit | 80c70bfb95cdbe0c644070f4ca4754a60f0a4830 (patch) | |
| tree | 79398b6fe665c89718f850cbfecef15e12bb7083 | |
| parent | fe7b87d908da33326fbf6fe2b3830426432ec66c (diff) | |
| download | linux-80c70bfb95cdbe0c644070f4ca4754a60f0a4830.tar.xz | |
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 <andersson@kernel.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://patch.msgid.link/20260108105619.3513561-2-andriy.shevchenko@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
| -rw-r--r-- | include/linux/scatterlist.h | 2 | ||||
| -rw-r--r-- | lib/scatterlist.c | 26 |
2 files changed, 28 insertions, 0 deletions
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 @@ -65,6 +65,32 @@ 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 * @nents: Number of entries in the scatterlist |