From c70759dcdd3d8abf746cb718dd606cb0fb18067a Mon Sep 17 00:00:00 2001
From: Warner Losh <imp@FreeBSD.org>
Date: Wed, 9 Aug 2006 18:25:07 +0000
Subject: [PATCH] Add pc98 specific code to adjust the firmware geometry when
 it differs from the actual geometry.  This enables support of disks larger
 than ~120GB on pc98 boxes.  They make great little network appliances. I've
 been using these changes for the past year or so on my network storage pc98
 box :-).

---
 sys/pc98/include/md_var.h    | 12 ++++++++++++
 sys/pc98/pc98/pc98_machdep.c | 38 ++++++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/sys/pc98/include/md_var.h b/sys/pc98/include/md_var.h
index 7d0fb726265..7ca6f3cc8cf 100644
--- a/sys/pc98/include/md_var.h
+++ b/sys/pc98/include/md_var.h
@@ -38,4 +38,16 @@
 extern	int	need_pre_dma_flush;
 extern	int	need_post_dma_flush;
 
+/*
+ * The ad driver maps the IDE disk's actual geometry to the firmware's
+ * notion of geometry.  However, PC98 machines need to do something
+ * different sometimes, so override the hook so we can do so.  We have to
+ * have a knowledge that a device_t is a struct device * here to avoid
+ * including too many things from this file.
+ */
+struct disk;
+struct device;
+void	pc98_ad_firmware_geom_adjust(struct device *, struct disk *);
+#define ad_firmware_geom_adjust(dev, dsk) pc98_ad_firmware_geom_adjust(dev, dsk)
+
 #endif /* !_PC98_INCLUDE_MD_VAR_H_ */
diff --git a/sys/pc98/pc98/pc98_machdep.c b/sys/pc98/pc98/pc98_machdep.c
index 2f2dfebbe43..badf6a3ed73 100644
--- a/sys/pc98/pc98/pc98_machdep.c
+++ b/sys/pc98/pc98/pc98_machdep.c
@@ -38,6 +38,11 @@
 
 #include <cam/cam.h>
 #include <cam/cam_ccb.h>
+#include <sys/bio.h>
+#include <sys/bus.h>
+#include <sys/conf.h>
+#include <geom/geom_disk.h>
+#include <machine/md_var.h>
 #include <pc98/pc98/pc98_machdep.h>
 
 /*
@@ -191,3 +196,36 @@ scsi_da_bios_params(struct ccb_calc_geometry *ccg)
 
 	return (0);
 }
+
+/*
+ * Get the geometry of the ATA HDD from the BIOS work area.
+ *
+ * XXX for now, we hack it
+ */
+void
+pc98_ad_firmware_geom_adjust(device_t dev, struct disk *disk)
+{
+	off_t totsec = disk->d_mediasize / disk->d_sectorsize;
+	off_t cyl = totsec / disk->d_fwsectors / disk->d_fwheads;
+    
+	/*
+	 * It is impossible to have more than 65535 cylendars, so if
+	 * we have more then try to adjust.  This is lame, but it is
+	 * only POC.
+	 */
+	if (cyl > 65355) {
+		if (totsec < 17*8*65535) {
+			disk->d_fwsectors = 17;
+			disk->d_fwheads = 8;
+		} else if (totsec < 63*16*65535) {
+			disk->d_fwsectors = 63;
+			disk->d_fwheads = 16;
+		} else if (totsec < 255*16*65535) {
+			disk->d_fwsectors = 255;
+			disk->d_fwheads = 16;
+		} else {
+			disk->d_fwsectors = 255;
+			disk->d_fwheads = 255;
+		}
+	}
+}