From: Andrei Borzenkov <arvidjaar@gmail.com>
Subject: [PATCH] biosdisk: debug output for disk parameters

Add debug output to track BIOS behavior with 4Kn disks.

---
 grub-core/disk/i386/pc/biosdisk.c | 45 +++++++++++++++++++++++++++++++++++----
 include/grub/i386/pc/biosdisk.h   |  1 +
 2 files changed, 42 insertions(+), 4 deletions(-)

diff --git a/grub-core/disk/i386/pc/biosdisk.c b/grub-core/disk/i386/pc/biosdisk.c
index f0aadd1..ef69f13 100644
--- a/grub-core/disk/i386/pc/biosdisk.c
+++ b/grub-core/disk/i386/pc/biosdisk.c
@@ -84,6 +84,8 @@ grub_biosdisk_rw_int13_extensions (int ah, int drive, void *dap)
 
   grub_bios_interrupt (0x13, &regs);
   return (regs.eax >> 8) & 0xff;
+  // return regs.flags & GRUB_CPU_INT_FLAGS_CARRY ? (regs.eax >> 8) & 0xff : 0;
+
 }
 
 /*
@@ -335,6 +337,7 @@ grub_biosdisk_open (const char *name, grub_disk_t disk)
   grub_uint64_t total_sectors = 0;
   int drive;
   struct grub_biosdisk_data *data;
+  int ret;
 
   drive = grub_biosdisk_get_drive (name);
   if (drive < 0)
@@ -369,11 +372,17 @@ grub_biosdisk_open (const char *name, grub_disk_t disk)
 	  struct grub_biosdisk_drp *drp
 	    = (struct grub_biosdisk_drp *) GRUB_MEMORY_MACHINE_SCRATCH_ADDR;
 
+	  grub_dprintf ("biosdisk", "%s: int13 version=%u\n", disk->name, version);
 	  /* Clear out the DRP.  */
 	  grub_memset (drp, 0, sizeof (*drp));
 	  drp->size = sizeof (*drp);
-	  if (! grub_biosdisk_get_diskinfo_int13_extensions (drive, drp))
+	  if (! (ret = grub_biosdisk_get_diskinfo_int13_extensions (drive, drp)))
 	    {
+	      grub_dprintf ("biosdisk", "%s: DRP size=%u flags=%x c=%u h=%u s=%u t=%"
+			    PRIuGRUB_UINT64_T " bpi=%u\n",
+			    disk->name, drp->size, drp->flags, drp->cylinders, drp->heads,
+			    drp->sectors, drp->total_sectors, drp->bytes_per_sector);
+
 	      data->flags = GRUB_BIOSDISK_FLAG_LBA;
 
 	      if (drp->total_sectors)
@@ -394,16 +403,22 @@ grub_biosdisk_open (const char *name, grub_disk_t disk)
 		       disk->log_sector_size++);
 		}
 	    }
+	  else
+	    grub_dprintf ("biosdisk", "%s: int13 get ext failed %x\n", disk->name, ret);
 	}
+      else
+	grub_dprintf ("biosdisk", "%s: int13 check ext failed\n", disk->name);
     }
 
   if (! (data->flags & GRUB_BIOSDISK_FLAG_CDROM))
     {
-      if (grub_biosdisk_get_diskinfo_standard (drive,
+      if ((ret = grub_biosdisk_get_diskinfo_standard (drive,
 					       &data->cylinders,
 					       &data->heads,
-					       &data->sectors) != 0)
+					       &data->sectors)) != 0)
         {
+	  grub_dprintf ("biosdisk", "%s: get_diskinfo failed %x\n", disk->name, ret);
+
 	  if (total_sectors && (data->flags & GRUB_BIOSDISK_FLAG_LBA))
 	    {
 	      data->sectors = 63;
@@ -419,6 +434,9 @@ grub_biosdisk_open (const char *name, grub_disk_t disk)
 	      return grub_error (GRUB_ERR_BAD_DEVICE, "%s cannot get C/H/S values", disk->name);
 	    }
         }
+      else
+	grub_dprintf ("biosdisk", "%s: C/H/S=%lu/%lu/%lu\n", disk->name,
+		      data->cylinders, data->heads, data->sectors);
 
       if (data->sectors == 0)
 	data->sectors = 63;
@@ -461,6 +479,7 @@ grub_biosdisk_rw (int cmd, grub_disk_t disk,
 		  unsigned segment)
 {
   struct grub_biosdisk_data *data = disk->data;
+  int ret;
 
   /* VirtualBox fails with sectors above 2T on CDs.
      Since even BD-ROMS are never that big anyway, return error.  */
@@ -501,19 +520,37 @@ grub_biosdisk_rw (int cmd, grub_disk_t disk,
 			       disk->name);
 	}
       else
-        if (grub_biosdisk_rw_int13_extensions (cmd + 0x42, data->drive, dap))
+        if ((ret = grub_biosdisk_rw_int13_extensions (cmd + 0x42, data->drive, dap)))
 	  {
+	    grub_dprintf ("biosdisk", "%s: ext sec=%" PRIuGRUB_UINT64_T " size=%"
+			  PRIuGRUB_SIZE " ret=%u\n",
+			  disk->name, sector, size, ret);
+
 	    /* Fall back to the CHS mode.  */
 	    data->flags &= ~GRUB_BIOSDISK_FLAG_LBA;
 	    disk->total_sectors = data->cylinders * data->heads * data->sectors;
 	    return grub_biosdisk_rw (cmd, disk, sector, size, segment);
 	  }
+	else if (!(data->flags & GRUB_BIOSDISK_FLAG_DPRINT))
+	  {
+	    grub_dprintf ("biosdisk", "%s: ext sec=%" PRIuGRUB_UINT64_T " size=%"
+			  PRIuGRUB_SIZE "\n",
+			  disk->name, sector, size);
+	      data->flags |= GRUB_BIOSDISK_FLAG_DPRINT;
+	  }
     }
   else
     {
       unsigned coff, hoff, soff;
       unsigned head;
 
+      if (!(data->flags & GRUB_BIOSDISK_FLAG_DPRINT))
+	{
+	  grub_dprintf ("biosdisk", "%s: legacy sec=%" PRIuGRUB_UINT64_T " size=%"
+			PRIuGRUB_SIZE "\n",
+			disk->name, sector, size);
+	  data->flags |= GRUB_BIOSDISK_FLAG_DPRINT;
+	}
       /* It is impossible to reach over 8064 MiB (a bit less than LBA24) with
 	 the traditional CHS access.  */
       if (sector >
diff --git a/include/grub/i386/pc/biosdisk.h b/include/grub/i386/pc/biosdisk.h
index 3d80716..fa0862f 100644
--- a/include/grub/i386/pc/biosdisk.h
+++ b/include/grub/i386/pc/biosdisk.h
@@ -24,6 +24,7 @@
 
 #define GRUB_BIOSDISK_FLAG_LBA	1
 #define GRUB_BIOSDISK_FLAG_CDROM 2
+#define GRUB_BIOSDISK_FLAG_DPRINT 4
 
 #define GRUB_BIOSDISK_CDTYPE_NO_EMUL	0
 #define GRUB_BIOSDISK_CDTYPE_1_2_M	1
-- 
tg: (0d663b5..) t/biosdisk (depends on: master)