struct scatterlist *sg, *prv;
unsigned int left;
+ memset(table, 0, sizeof(*table));
+
+ if (nents == 0)
+ return -EINVAL;
#ifndef ARCH_HAS_SG_CHAIN
if (WARN_ON_ONCE(nents > max_ents))
return -EINVAL;
#endif
- memset(table, 0, sizeof(*table));
-
left = nents;
prv = NULL;
do {
}
EXPORT_SYMBOL(sg_miter_start);
+static bool sg_miter_get_next_page(struct sg_mapping_iter *miter)
+{
+ if (!miter->__remaining) {
+ struct scatterlist *sg;
+ unsigned long pgoffset;
+
+ if (!__sg_page_iter_next(&miter->piter))
+ return false;
+
+ sg = miter->piter.sg;
+ pgoffset = miter->piter.sg_pgoffset;
+
+ miter->__offset = pgoffset ? 0 : sg->offset;
+ miter->__remaining = sg->offset + sg->length -
+ (pgoffset << PAGE_SHIFT) - miter->__offset;
+ miter->__remaining = min_t(unsigned long, miter->__remaining,
+ PAGE_SIZE - miter->__offset);
+ }
+
+ return true;
+}
+
+/**
+ * sg_miter_skip - reposition mapping iterator
+ * @miter: sg mapping iter to be skipped
+ * @offset: number of bytes to plus the current location
+ *
+ * Description:
+ * Sets the offset of @miter to its current location plus @offset bytes.
+ * If mapping iterator @miter has been proceeded by sg_miter_next(), this
+ * stops @miter.
+ *
+ * Context:
+ * Don't care if @miter is stopped, or not proceeded yet.
+ * Otherwise, preemption disabled if the SG_MITER_ATOMIC is set.
+ *
+ * Returns:
+ * true if @miter contains the valid mapping. false if end of sg
+ * list is reached.
+ */
+static bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset)
+{
+ sg_miter_stop(miter);
+
+ while (offset) {
+ off_t consumed;
+
+ if (!sg_miter_get_next_page(miter))
+ return false;
+
+ consumed = min_t(off_t, offset, miter->__remaining);
+ miter->__offset += consumed;
+ miter->__remaining -= consumed;
+ offset -= consumed;
+ }
+
+ return true;
+}
+
/**
* sg_miter_next - proceed mapping iterator to the next mapping
* @miter: sg mapping iter to proceed
* Get to the next page if necessary.
* __remaining, __offset is adjusted by sg_miter_stop
*/
- if (!miter->__remaining) {
- struct scatterlist *sg;
- unsigned long pgoffset;
-
- if (!__sg_page_iter_next(&miter->piter))
- return false;
-
- sg = miter->piter.sg;
- pgoffset = miter->piter.sg_pgoffset;
+ if (!sg_miter_get_next_page(miter))
+ return false;
- miter->__offset = pgoffset ? 0 : sg->offset;
- miter->__remaining = sg->offset + sg->length -
- (pgoffset << PAGE_SHIFT) - miter->__offset;
- miter->__remaining = min_t(unsigned long, miter->__remaining,
- PAGE_SIZE - miter->__offset);
- }
miter->page = sg_page_iter_page(&miter->piter);
miter->consumed = miter->length = miter->__remaining;
* @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
+ * @skip: Number of bytes to skip before copying
+ * @to_buffer: transfer direction (true == from an sg list to a
+ * buffer, false == 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)
+ void *buf, size_t buflen, off_t skip,
+ bool to_buffer)
{
unsigned int offset = 0;
struct sg_mapping_iter miter;
sg_miter_start(&miter, sgl, nents, sg_flags);
+ if (!sg_miter_skip(&miter, skip))
+ return false;
+
local_irq_save(flags);
while (sg_miter_next(&miter) && offset < buflen) {
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);
+ return sg_copy_buffer(sgl, nents, buf, buflen, 0, false);
}
EXPORT_SYMBOL(sg_copy_from_buffer);
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);
+ return sg_copy_buffer(sgl, nents, buf, buflen, 0, true);
}
EXPORT_SYMBOL(sg_copy_to_buffer);
+
+/**
+ * sg_pcopy_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
+ * @skip: Number of bytes to skip before copying
+ * @buflen: The number of bytes to copy
+ *
+ * Returns the number of copied bytes.
+ *
+ **/
+size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
+ void *buf, size_t buflen, off_t skip)
+{
+ return sg_copy_buffer(sgl, nents, buf, buflen, skip, false);
+}
+EXPORT_SYMBOL(sg_pcopy_from_buffer);
+
+/**
+ * sg_pcopy_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
+ * @skip: Number of bytes to skip before copying
+ * @buflen: The number of bytes to copy
+ *
+ * Returns the number of copied bytes.
+ *
+ **/
+size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
+ void *buf, size_t buflen, off_t skip)
+{
+ return sg_copy_buffer(sgl, nents, buf, buflen, skip, true);
+}
+EXPORT_SYMBOL(sg_pcopy_to_buffer);
projects / cascardo / linux.git / blobdiff