Merge branch 'next' of git://git.monstr.eu/linux-2.6-microblaze

[~andy/linux] / lib / scatterlist.c

diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index c35b929435f302ab555f6c37fc68637df2c0666f..a685c8a79578b274cb361d442b953507e58d7d63 100644 (file)
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -247,13 +247,15 @@ int __sg_alloc_table(struct sg_table *table, unsigned int nents,
        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 {
@@ -475,6 +477,43 @@ static bool sg_miter_get_next_page(struct sg_mapping_iter *miter)
        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
@@ -561,14 +600,16 @@ EXPORT_SYMBOL(sg_miter_stop);
  * @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;
@@ -582,6 +623,9 @@ static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
 
        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) {
@@ -616,7 +660,7 @@ static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
 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);
 
@@ -633,6 +677,42 @@ 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);