diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/scatterlist.c | 102 |
1 files changed, 102 insertions, 0 deletions
diff --git a/lib/scatterlist.c b/lib/scatterlist.c index acca4901..b80c211 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -8,6 +8,7 @@ */ #include <linux/module.h> #include <linux/scatterlist.h> +#include <linux/highmem.h> /** * sg_next - return the next scatterlist entry in a list @@ -292,3 +293,104 @@ int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask) return ret; } EXPORT_SYMBOL(sg_alloc_table); + +/** + * sg_copy_buffer - Copy data between a linear buffer and an SG list + * @sgl: The SG list + * @nents: Number of SG entries + * @buf: Where to copy from + * @buflen: The number of bytes to copy + * @to_buffer: transfer direction (non zero == from an sg list to a + * buffer, 0 == from a buffer to an sg list + * + * Returns the number of copied bytes. + * + **/ +static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, + void *buf, size_t buflen, int to_buffer) +{ + struct scatterlist *sg; + size_t buf_off = 0; + int i; + + WARN_ON(!irqs_disabled()); + + for_each_sg(sgl, sg, nents, i) { + struct page *page; + int n = 0; + unsigned int sg_off = sg->offset; + unsigned int sg_copy = sg->length; + + if (sg_copy > buflen) + sg_copy = buflen; + buflen -= sg_copy; + + while (sg_copy > 0) { + unsigned int page_copy; + void *p; + + page_copy = PAGE_SIZE - sg_off; + if (page_copy > sg_copy) + page_copy = sg_copy; + + page = nth_page(sg_page(sg), n); + p = kmap_atomic(page, KM_BIO_SRC_IRQ); + + if (to_buffer) + memcpy(buf + buf_off, p + sg_off, page_copy); + else { + memcpy(p + sg_off, buf + buf_off, page_copy); + flush_kernel_dcache_page(page); + } + + kunmap_atomic(p, KM_BIO_SRC_IRQ); + + buf_off += page_copy; + sg_off += page_copy; + if (sg_off == PAGE_SIZE) { + sg_off = 0; + n++; + } + sg_copy -= page_copy; + } + + if (!buflen) + break; + } + + return buf_off; +} + +/** + * sg_copy_from_buffer - Copy from a linear buffer to an SG list + * @sgl: The SG list + * @nents: Number of SG entries + * @buf: Where to copy from + * @buflen: The number of bytes to copy + * + * Returns the number of copied bytes. + * + **/ +size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents, + void *buf, size_t buflen) +{ + return sg_copy_buffer(sgl, nents, buf, buflen, 0); +} +EXPORT_SYMBOL(sg_copy_from_buffer); + +/** + * sg_copy_to_buffer - Copy from an SG list to a linear buffer + * @sgl: The SG list + * @nents: Number of SG entries + * @buf: Where to copy to + * @buflen: The number of bytes to copy + * + * Returns the number of copied bytes. + * + **/ +size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents, + void *buf, size_t buflen) +{ + return sg_copy_buffer(sgl, nents, buf, buflen, 1); +} +EXPORT_SYMBOL(sg_copy_to_buffer); |
