diff options
| author | Andy Shevchenko <andriy.shevchenko@linux.intel.com> | 2026-01-08 11:50:12 +0100 |
|---|---|---|
| committer | Vinod Koul <vkoul@kernel.org> | 2026-01-09 08:36:00 +0530 |
| commit | 80c70bfb95cdbe0c644070f4ca4754a60f0a4830 (patch) | |
| tree | 79398b6fe665c89718f850cbfecef15e12bb7083 /lib | |
| parent | fe7b87d908da33326fbf6fe2b3830426432ec66c (diff) | |
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>
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/scatterlist.c | 26 |
1 files changed, 26 insertions, 0 deletions
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 |