[PATCH 3/4] libata: trailing data handling fix for __atapi_pio_bytes()

[Albert Lee <albertcc@tw.ibm.com>]

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Hi Jeff,

Resend the patch #3.

Problem:
    Sometimes CD-ROM drives will ask/return more data than expected.

Changes:
- Handle the trailing data if the end of qc->sg has been reached.


Albert

Signed-off-by: Albert Lee <albertcc@tw.ibm.com>


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--- 12_atapi_pio_if_condition_fix/drivers/scsi/libata-core.c	2005-06-06 13:52:11.000000000 +0800
+++ 13_atapi_pio_trailing_data_handling/drivers/scsi/libata-core.c	2005-06-09 11:05:10.000000000 +0800
@@ -2575,6 +2575,23 @@
 		ap->pio_task_state = PIO_ST_LAST;
 
 next_sg:
+	/* check whether qc->sg is full */
+	if (unlikely(qc->cursg >= qc->n_elem)) {
+		unsigned char pad_buf[2];
+		unsigned int words = bytes >> 1;
+		unsigned int i;
+
+		DPRINTK("ata%u: padding %u bytes\n", ap->id, bytes);
+
+		memset(&pad_buf, 0, sizeof(pad_buf));
+		for (i = 0; i < words; i++) {
+			ata_data_xfer(ap, pad_buf, sizeof(pad_buf), do_write);
+		}
+
+		ap->pio_task_state = PIO_ST_LAST;
+		return;
+	}
+
 	sg = &qc->sg[qc->cursg];
 
 	page = sg->page;