[PATCH] libata handle the case when device returns/needs extra data
PATCH 2/2: handle the case when device returns/needs extra data
Description:
Sometimes the device returns/needs extra data than expected.
Changes:
Modify __atapi_pio_bytes() to handle the case where device returns/needs extra data.
- for read case, discard trailing data from the device
- for write case, padding zero data to the device
Signed-off-by: Albert Lee <albertcc@tw.ibm.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>
diff --git a/drivers/scsi/libata-core.c b/drivers/scsi/libata-core.c
index 8f6e536..9add4c5 100644
--- a/drivers/scsi/libata-core.c
+++ b/drivers/scsi/libata-core.c
@@ -2697,10 +2697,33 @@
unsigned char *buf;
unsigned int offset, count;
- if (qc->curbytes == qc->nbytes - bytes)
+ if (qc->curbytes + bytes >= qc->nbytes)
ap->pio_task_state = PIO_ST_LAST;
next_sg:
+ if (unlikely(qc->cursg >= qc->n_elem)) {
+ /*
+ * The end of qc->sg is reached and the device expects
+ * more data to transfer. In order not to overrun qc->sg
+ * and fulfill length specified in the byte count register,
+ * - for read case, discard trailing data from the device
+ * - for write case, padding zero data to the device
+ */
+ u16 pad_buf[1] = { 0 };
+ unsigned int words = bytes >> 1;
+ unsigned int i;
+
+ if (words) /* warning if bytes > 1 */
+ printk(KERN_WARNING "ata%u: %u bytes trailing data\n",
+ ap->id, bytes);
+
+ for (i = 0; i < words; i++)
+ ata_data_xfer(ap, (unsigned char*)pad_buf, 2, do_write);
+
+ ap->pio_task_state = PIO_ST_LAST;
+ return;
+ }
+
sg = &qc->sg[qc->cursg];
page = sg->page;
@@ -2734,9 +2757,8 @@
kunmap(page);
- if (bytes) {
+ if (bytes)
goto next_sg;
- }
}
/**