diff options
| -rw-r--r-- | include/linux/scatterlist.h | 5 | ||||
| -rw-r--r-- | lib/Kconfig | 7 | ||||
| -rw-r--r-- | lib/Makefile | 1 | ||||
| -rw-r--r-- | lib/sg_split.c | 202 |
4 files changed, 215 insertions, 0 deletions
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index 698e906ca730..556ec1ea2574 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -247,6 +247,11 @@ struct scatterlist *sg_next(struct scatterlist *); 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); +int sg_split(struct scatterlist *in, const int in_mapped_nents, + const off_t skip, const int nb_splits, + const size_t *split_sizes, + struct scatterlist **out, int *out_mapped_nents, + gfp_t gfp_mask); typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t); typedef void (sg_free_fn)(struct scatterlist *, unsigned int); diff --git a/lib/Kconfig b/lib/Kconfig index 3a2ef67db6c7..dc516164415a 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -521,6 +521,13 @@ config UCS2_STRING source "lib/fonts/Kconfig" +config SG_SPLIT + def_bool n + help + Provides a heler to split scatterlists into chunks, each chunk being a + scatterlist. This should be selected by a driver or an API which + whishes to split a scatterlist amongst multiple DMA channel. + # # sg chaining option # diff --git a/lib/Makefile b/lib/Makefile index 6897b527581a..2ee6ea2e9b08 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -160,6 +160,7 @@ obj-$(CONFIG_GENERIC_STRNLEN_USER) += strnlen_user.o obj-$(CONFIG_GENERIC_NET_UTILS) += net_utils.o +obj-$(CONFIG_SG_SPLIT) += sg_split.o obj-$(CONFIG_STMP_DEVICE) += stmp_device.o libfdt_files = fdt.o fdt_ro.o fdt_wip.o fdt_rw.o fdt_sw.o fdt_strerror.o \ diff --git a/lib/sg_split.c b/lib/sg_split.c new file mode 100644 index 000000000000..b063410c3593 --- /dev/null +++ b/lib/sg_split.c @@ -0,0 +1,202 @@ +/* + * Copyright (C) 2015 Robert Jarzmik <robert.jarzmik@free.fr> + * + * Scatterlist splitting helpers. + * + * This source code is licensed under the GNU General Public License, + * Version 2. See the file COPYING for more details. + */ + +#include <linux/scatterlist.h> +#include <linux/slab.h> + +struct sg_splitter { + struct scatterlist *in_sg0; + int nents; + off_t skip_sg0; + unsigned int length_last_sg; + + struct scatterlist *out_sg; +}; + +static int sg_calculate_split(struct scatterlist *in, int nents, int nb_splits, + off_t skip, const size_t *sizes, + struct sg_splitter *splitters, bool mapped) +{ + int i; + unsigned int sglen; + size_t size = sizes[0], len; + struct sg_splitter *curr = splitters; + struct scatterlist *sg; + + for (i = 0; i < nb_splits; i++) { + splitters[i].in_sg0 = NULL; + splitters[i].nents = 0; + } + + for_each_sg(in, sg, nents, i) { + sglen = mapped ? sg_dma_len(sg) : sg->length; + if (skip > sglen) { + skip -= sglen; + continue; + } + + len = min_t(size_t, size, sglen - skip); + if (!curr->in_sg0) { + curr->in_sg0 = sg; + curr->skip_sg0 = skip; + } + size -= len; + curr->nents++; + curr->length_last_sg = len; + + while (!size && (skip + len < sglen) && (--nb_splits > 0)) { + curr++; + size = *(++sizes); + skip += len; + len = min_t(size_t, size, sglen - skip); + + curr->in_sg0 = sg; + curr->skip_sg0 = skip; + curr->nents = 1; + curr->length_last_sg = len; + size -= len; + } + skip = 0; + + if (!size && --nb_splits > 0) { + curr++; + size = *(++sizes); + } + + if (!nb_splits) + break; + } + + return (size || !splitters[0].in_sg0) ? -EINVAL : 0; +} + +static void sg_split_phys(struct sg_splitter *splitters, const int nb_splits) +{ + int i, j; + struct scatterlist *in_sg, *out_sg; + struct sg_splitter *split; + + for (i = 0, split = splitters; i < nb_splits; i++, split++) { + in_sg = split->in_sg0; + out_sg = split->out_sg; + for (j = 0; j < split->nents; j++, out_sg++) { + *out_sg = *in_sg; + if (!j) { + out_sg->offset += split->skip_sg0; + out_sg->length -= split->skip_sg0; + } else { + out_sg->offset = 0; + } + sg_dma_address(out_sg) = 0; + sg_dma_len(out_sg) = 0; + in_sg = sg_next(in_sg); + } + out_sg[-1].length = split->length_last_sg; + sg_mark_end(out_sg - 1); + } +} + +static void sg_split_mapped(struct sg_splitter *splitters, const int nb_splits) +{ + int i, j; + struct scatterlist *in_sg, *out_sg; + struct sg_splitter *split; + + for (i = 0, split = splitters; i < nb_splits; i++, split++) { + in_sg = split->in_sg0; + out_sg = split->out_sg; + for (j = 0; j < split->nents; j++, out_sg++) { + sg_dma_address(out_sg) = sg_dma_address(in_sg); + sg_dma_len(out_sg) = sg_dma_len(in_sg); + if (!j) { + sg_dma_address(out_sg) += split->skip_sg0; + sg_dma_len(out_sg) -= split->skip_sg0; + } + in_sg = sg_next(in_sg); + } + sg_dma_len(--out_sg) = split->length_last_sg; + } +} + +/** + * sg_split - split a scatterlist into several scatterlists + * @in: the input sg list + * @in_mapped_nents: the result of a dma_map_sg(in, ...), or 0 if not mapped. + * @skip: the number of bytes to skip in the input sg list + * @nb_splits: the number of desired sg outputs + * @split_sizes: the respective size of each output sg list in bytes + * @out: an array where to store the allocated output sg lists + * @out_mapped_nents: the resulting sg lists mapped number of sg entries. Might + * be NULL if sglist not already mapped (in_mapped_nents = 0) + * @gfp_mask: the allocation flag + * + * This function splits the input sg list into nb_splits sg lists, which are + * allocated and stored into out. + * The @in is split into : + * - @out[0], which covers bytes [@skip .. @skip + @split_sizes[0] - 1] of @in + * - @out[1], which covers bytes [@skip + split_sizes[0] .. + * @skip + @split_sizes[0] + @split_sizes[1] -1] + * etc ... + * It will be the caller's duty to kfree() out array members. + * + * Returns 0 upon success, or error code + */ +int sg_split(struct scatterlist *in, const int in_mapped_nents, + const off_t skip, const int nb_splits, + const size_t *split_sizes, + struct scatterlist **out, int *out_mapped_nents, + gfp_t gfp_mask) +{ + int i, ret; + struct sg_splitter *splitters; + + splitters = kcalloc(nb_splits, sizeof(*splitters), gfp_mask); + if (!splitters) + return -ENOMEM; + + ret = sg_calculate_split(in, sg_nents(in), nb_splits, skip, split_sizes, + splitters, false); + if (ret < 0) + goto err; + + ret = -ENOMEM; + for (i = 0; i < nb_splits; i++) { + splitters[i].out_sg = kmalloc_array(splitters[i].nents, + sizeof(struct scatterlist), + gfp_mask); + if (!splitters[i].out_sg) + goto err; + } + + /* + * The order of these 3 calls is important and should be kept. + */ + sg_split_phys(splitters, nb_splits); + ret = sg_calculate_split(in, in_mapped_nents, nb_splits, skip, + split_sizes, splitters, true); + if (ret < 0) + goto err; + sg_split_mapped(splitters, nb_splits); + + for (i = 0; i < nb_splits; i++) { + out[i] = splitters[i].out_sg; + if (out_mapped_nents) + out_mapped_nents[i] = splitters[i].nents; + } + + kfree(splitters); + return 0; + +err: + for (i = 0; i < nb_splits; i++) + kfree(splitters[i].out_sg); + kfree(splitters); + return ret; +} +EXPORT_SYMBOL(sg_split); |