The MODE SELECT command can contain an optional block descriptor that can be used
to set the device block size. If the block descriptor is present then update the
block size on the SCSI device accordingly.

This allows CDROMs to be used with A/UX which requires a CDROM drive which is
capable of switching from a 2048 byte sector size to a 512 byte sector size.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
---
 hw/scsi/scsi-disk.c  | 6 ++++++
 hw/scsi/trace-events | 1 +
 2 files changed, 7 insertions(+)

diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
index 3659583e13..9c8bad0283 100644
--- a/hw/scsi/scsi-disk.c
+++ b/hw/scsi/scsi-disk.c
@@ -1616,6 +1616,12 @@ static void scsi_disk_emulate_mode_select(SCSIDiskReq *r, uint8_t *inbuf)
         goto invalid_param;
     }
 
+    /* Allow changing the block size */
+    if (bd_len && p[6] != (s->qdev.blocksize >> 8)) {
+        s->qdev.blocksize = p[6] << 8;
+        trace_scsi_disk_mode_select_set_blocksize(s->qdev.blocksize);
+    }
+
     len -= bd_len;
     p += bd_len;
 
diff --git a/hw/scsi/trace-events b/hw/scsi/trace-events
index 8e927ff62d..ab238293f0 100644
--- a/hw/scsi/trace-events
+++ b/hw/scsi/trace-events
@@ -340,6 +340,7 @@ scsi_disk_dma_command_WRITE(const char *cmd, uint64_t lba, int len) "Write %s(se
 scsi_disk_new_request(uint32_t lun, uint32_t tag, const char *line) "Command: lun=%d tag=0x%x data=%s"
 scsi_disk_aio_sgio_command(uint32_t tag, uint8_t cmd, uint64_t lba, int len, uint32_t timeout) "disk aio sgio: tag=0x%x cmd=0x%x (sector %" PRId64 ", count %d) timeout=%u"
 scsi_disk_mode_select_page_truncated(int page, int len, int page_len) "page %d expected length %d but received length %d"
+scsi_disk_mode_select_set_blocksize(int blocksize) "set block size to %d"
 
 # scsi-generic.c
 scsi_generic_command_complete_noio(void *req, uint32_t tag, int statuc) "Command complete %p tag=0x%x status=%d"
-- 
2.30.2