USB storage: sg chaining support
[PATCH] USB storage: sg chaining support
Modify usb_stor_access_xfer_buf() to take a pointer to an sg
entry pointer, so we can keep track of that instead of passing
around an integer index (which we can't use when dealing with
multiple scatterlist arrays).
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/drivers/usb/storage/protocol.c b/drivers/usb/storage/protocol.c
index 9ad3042..cc8f7c5 100644
--- a/drivers/usb/storage/protocol.c
+++ b/drivers/usb/storage/protocol.c
@@ -157,7 +157,7 @@
* pick up from where this one left off. */
unsigned int usb_stor_access_xfer_buf(unsigned char *buffer,
- unsigned int buflen, struct scsi_cmnd *srb, unsigned int *index,
+ unsigned int buflen, struct scsi_cmnd *srb, struct scatterlist **sgptr,
unsigned int *offset, enum xfer_buf_dir dir)
{
unsigned int cnt;
@@ -184,16 +184,17 @@
* located in high memory -- then kmap() will map it to a temporary
* position in the kernel's virtual address space. */
} else {
- struct scatterlist *sg =
- (struct scatterlist *) srb->request_buffer
- + *index;
+ struct scatterlist *sg = *sgptr;
+
+ if (!sg)
+ sg = (struct scatterlist *) srb->request_buffer;
/* This loop handles a single s-g list entry, which may
* include multiple pages. Find the initial page structure
* and the starting offset within the page, and update
* the *offset and *index values for the next loop. */
cnt = 0;
- while (cnt < buflen && *index < srb->use_sg) {
+ while (cnt < buflen) {
struct page *page = sg->page +
((sg->offset + *offset) >> PAGE_SHIFT);
unsigned int poff =
@@ -209,8 +210,7 @@
/* Transfer continues to next s-g entry */
*offset = 0;
- ++*index;
- ++sg;
+ sg = sg_next(sg);
}
/* Transfer the data for all the pages in this
@@ -234,6 +234,7 @@
sglen -= plen;
}
}
+ *sgptr = sg;
}
/* Return the amount actually transferred */
@@ -245,9 +246,10 @@
void usb_stor_set_xfer_buf(unsigned char *buffer,
unsigned int buflen, struct scsi_cmnd *srb)
{
- unsigned int index = 0, offset = 0;
+ unsigned int offset = 0;
+ struct scatterlist *sg = NULL;
- usb_stor_access_xfer_buf(buffer, buflen, srb, &index, &offset,
+ usb_stor_access_xfer_buf(buffer, buflen, srb, &sg, &offset,
TO_XFER_BUF);
if (buflen < srb->request_bufflen)
srb->resid = srb->request_bufflen - buflen;