Hello all,
I've got an application that depends on the residual data information in
order to send it to another application. The basic problem is that if a
single SCSI transfer size is greater than a single scatter gather region
(generally ~32k), then the residual length is based on the size of the
scatter gather regions and not the request size. When the two differ, and
there is a residual data condition the application computes the transfer size
incorrectly.
The attached patch is against the sym53c8xx.c driver in the 2.4 tree, I
haven't tested the 2.6 sym53c8xx_2 driver, but a quick glance at the code
seems to indicate it has the same problem. When I get a chance, I will test
the 2.6 driver as well, for the same problem. The patch basically saves the
original request length into a new member in the ccb structure called
orig_data_len. Then, when the residual len is being computed, it adjusts it
for the original data request size.
BTW: We are using the old sym53c8xx driver instead of the new one, because it
passes more of our validation tests in 2.4 than the sym53c8xx_2 driver does.
Our tests use the sg interface exclusively, so I'm not sure about behavior
with other drivers (st,sd).
--- sym53c8xx.c.orig 2006-10-04 18:40:39.132184101 -0500
+++ sym53c8xx.c 2006-10-05 12:20:48.252759592 -0500
@@ -1990,6 +1990,9 @@
int ext_sg; /* Extreme data pointer, used */
int ext_ofs; /* to calculate the residual. */
int resid;
+ int orig_data_len; /* used to calculate the correct*/
+ /* resid based on the original */
+ /* data len, not the scatter len*/
};
#define CCB_PHYS(cp,lbl) (cp->p_ccb + offsetof(struct ccb, lbl))
@@ -10666,8 +10669,8 @@
** unknown), then no data transfer should have
** taken place.
*/
- if (cp->phys.header.lastp == NCB_SCRIPTH_PHYS (np, data_io))
- return cp->data_len;
+ if (cp->phys.header.lastp == NCB_SCRIPTH_PHYS (np, data_io))
+ return cp->orig_data_len;
/*
** If no data transfer occurs, or if the data
@@ -10676,7 +10679,7 @@
if (cp->startp == cp->phys.header.lastp ||
ncr_evaluate_dp(np, cp, scr_to_cpu(cp->phys.header.lastp),
&dp_ofs) < 0) {
- return cp->data_len;
+ return cp->orig_data_len;
}
/*
@@ -10685,14 +10688,13 @@
*/
dp_sgmin = MAX_SCATTER - cp->segments;
resid = -cp->ext_ofs;
- for (dp_sg = cp->ext_sg; dp_sg < MAX_SCATTER; ++dp_sg) {
+ for (dp_sg = cp->ext_sg; dp_sg < MAX_SCATTER; ++dp_sg) {
tmp = scr_to_cpu(cp->phys.data[dp_sg].size);
resid += (tmp & 0xffffff);
}
-
- /*
- ** Hopefully, the result is not too wrong.
- */
+
+ /* adjust based on original data length */
+ resid=cp->orig_data_len-(cp->data_len-resid);
return resid;
}
@@ -12096,6 +12098,7 @@
int segment;
cp->data_len = cmd->request_bufflen;
+ cp->orig_data_len = cmd->request_bufflen;
if (cmd->request_bufflen) {
dma_addr_t baddr = map_scsi_single_data(np, cmd);
@@ -12136,6 +12139,7 @@
int use_sg = (int) cmd->use_sg;
cp->data_len = 0;
+ cp->orig_data_len = cmd->request_bufflen;
if (!use_sg)
segn = ncr_scatter_no_sglist(np, cp, cmd);
@@ -12175,6 +12179,7 @@
int use_sg = (int) cmd->use_sg;
cp->data_len = 0;
+ cp->orig_data_len = cmd->request_bufflen;
if (!use_sg)
segment = ncr_scatter_no_sglist(np, cp, cmd);
@@ -12191,9 +12196,7 @@
dma_addr_t baddr = scsi_sg_dma_address(&scatter[segment]);
unsigned int len = scsi_sg_dma_len(&scatter[segment]);
- SCATTER_ONE(&data[segment],
- baddr,
- len);
+ SCATTER_ONE(&data[segment], baddr, len);
cp->data_len += len;
}
}
