[PATCH] NCR5380: Support chained sg lists

[Finn Thain]

My understanding is that support for chained scatterlists is to
become mandatory for LLDs.

Cc: Michael Schmitz <schmitz...@gmail.com>
Signed-off-by: Finn Thain <fth...@telegraphics.com.au>
---
 drivers/scsi/NCR5380.c | 41 ++++++++++++++++++-----------------------
 1 file changed, 18 insertions(+), 23 deletions(-)

diff --git a/drivers/scsi/NCR5380.c b/drivers/scsi/NCR5380.c
index d9fa9cf2fd8b..536426f25e86 100644
--- a/drivers/scsi/NCR5380.c
+++ b/drivers/scsi/NCR5380.c
@@ -149,12 +149,10 @@ static inline void initialize_SCp(struct scsi_cmnd *cmd)
 
        if (scsi_bufflen(cmd)) {
                cmd->SCp.buffer = scsi_sglist(cmd);
-               cmd->SCp.buffers_residual = scsi_sg_count(cmd) - 1;
                cmd->SCp.ptr = sg_virt(cmd->SCp.buffer);
                cmd->SCp.this_residual = cmd->SCp.buffer->length;
        } else {
                cmd->SCp.buffer = NULL;
-               cmd->SCp.buffers_residual = 0;
                cmd->SCp.ptr = NULL;
                cmd->SCp.this_residual = 0;
        }
@@ -163,6 +161,17 @@ static inline void initialize_SCp(struct scsi_cmnd *cmd)
        cmd->SCp.Message = 0;
 }
 
+static inline void advance_sg_buffer(struct scsi_cmnd *cmd)
+{
+       struct scatterlist *s = cmd->SCp.buffer;
+
+       if (!cmd->SCp.this_residual && s && !sg_is_last(s)) {
+               cmd->SCp.buffer = sg_next(s);
+               cmd->SCp.ptr = sg_virt(cmd->SCp.buffer);
+               cmd->SCp.this_residual = cmd->SCp.buffer->length;
+       }
+}
+
 /**
  * NCR5380_poll_politely2 - wait for two chip register values
  * @hostdata: host private data
@@ -1670,12 +1679,7 @@ static void NCR5380_information_transfer(struct 
Scsi_Host *instance)
                            sun3_dma_setup_done != cmd) {
                                int count;
 
-                               if (!cmd->SCp.this_residual && 
cmd->SCp.buffers_residual) {
-                                       ++cmd->SCp.buffer;
-                                       --cmd->SCp.buffers_residual;
-                                       cmd->SCp.this_residual = 
cmd->SCp.buffer->length;
-                                       cmd->SCp.ptr = sg_virt(cmd->SCp.buffer);
-                               }
+                               advance_sg_buffer(cmd);
 
                                count = sun3scsi_dma_xfer_len(hostdata, cmd);
 
@@ -1725,15 +1729,11 @@ static void NCR5380_information_transfer(struct 
Scsi_Host *instance)
                                 * scatter-gather list, move onto the next one.
                                 */
 
-                               if (!cmd->SCp.this_residual && 
cmd->SCp.buffers_residual) {
-                                       ++cmd->SCp.buffer;
-                                       --cmd->SCp.buffers_residual;
-                                       cmd->SCp.this_residual = 
cmd->SCp.buffer->length;
-                                       cmd->SCp.ptr = sg_virt(cmd->SCp.buffer);
-                                       dsprintk(NDEBUG_INFORMATION, instance, 
"%d bytes and %d buffers left\n",
-                                                cmd->SCp.this_residual,
-                                                cmd->SCp.buffers_residual);
-                               }
+                               advance_sg_buffer(cmd);
+                               dsprintk(NDEBUG_INFORMATION, instance,
+                                       "this residual %d, sg ents %d\n",
+                                       cmd->SCp.this_residual,
+                                       sg_nents(cmd->SCp.buffer));
 
                                /*
                                 * The preferred transfer method is going to be
@@ -2126,12 +2126,7 @@ static void NCR5380_reselect(struct Scsi_Host *instance)
        if (sun3_dma_setup_done != tmp) {
                int count;
 
-               if (!tmp->SCp.this_residual && tmp->SCp.buffers_residual) {
-                       ++tmp->SCp.buffer;
-                       --tmp->SCp.buffers_residual;
-                       tmp->SCp.this_residual = tmp->SCp.buffer->length;
-                       tmp->SCp.ptr = sg_virt(tmp->SCp.buffer);
-               }
+               advance_sg_buffer(tmp);
 
                count = sun3scsi_dma_xfer_len(hostdata, tmp);
 
-- 
2.21.0