Abstract out geometry detection code from IDE for reuse

Virtio will want to use the geometry detection code.  It doesn't belong 
in ide.c anyway.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5797 c046a42c-6fe2-441c-8c8c-71466251a162

1 files changed, 116 insertions, 0 deletions

diff --git a/block.c b/block.c
index 0f1734e..dadf3cd 100644
--- a/block.c
+++ b/block.c
@@ -739,6 +739,122 @@ void bdrv_get_geometry(BlockDriverState *bs, uint64_t *nb_sectors_ptr)
     *nb_sectors_ptr = length;
 }
 
+struct partition {
+        uint8_t boot_ind;           /* 0x80 - active */
+        uint8_t head;               /* starting head */
+        uint8_t sector;             /* starting sector */
+        uint8_t cyl;                /* starting cylinder */
+        uint8_t sys_ind;            /* What partition type */
+        uint8_t end_head;           /* end head */
+        uint8_t end_sector;         /* end sector */
+        uint8_t end_cyl;            /* end cylinder */
+        uint32_t start_sect;        /* starting sector counting from 0 */
+        uint32_t nr_sects;          /* nr of sectors in partition */
+} __attribute__((packed));
+
+/* try to guess the disk logical geometry from the MSDOS partition table. Return 0 if OK, -1 if could not guess */
+static int guess_disk_lchs(BlockDriverState *bs,
+                           int *pcylinders, int *pheads, int *psectors)
+{
+    uint8_t buf[512];
+    int ret, i, heads, sectors, cylinders;
+    struct partition *p;
+    uint32_t nr_sects;
+    int64_t nb_sectors;
+
+    bdrv_get_geometry(bs, &nb_sectors);
+
+    ret = bdrv_read(bs, 0, buf, 1);
+    if (ret < 0)
+        return -1;
+    /* test msdos magic */
+    if (buf[510] != 0x55 || buf[511] != 0xaa)
+        return -1;
+    for(i = 0; i < 4; i++) {
+        p = ((struct partition *)(buf + 0x1be)) + i;
+        nr_sects = le32_to_cpu(p->nr_sects);
+        if (nr_sects && p->end_head) {
+            /* We make the assumption that the partition terminates on
+               a cylinder boundary */
+            heads = p->end_head + 1;
+            sectors = p->end_sector & 63;
+            if (sectors == 0)
+                continue;
+            cylinders = nb_sectors / (heads * sectors);
+            if (cylinders < 1 || cylinders > 16383)
+                continue;
+            *pheads = heads;
+            *psectors = sectors;
+            *pcylinders = cylinders;
+#if 0
+            printf("guessed geometry: LCHS=%d %d %d\n",
+                   cylinders, heads, sectors);
+#endif
+            return 0;
+        }
+    }
+    return -1;
+}
+
+void bdrv_guess_geometry(BlockDriverState *bs, int *pcyls, int *pheads, int *psecs)
+{
+    int translation, lba_detected = 0;
+    int cylinders, heads, secs;
+    int64_t nb_sectors;
+
+    /* if a geometry hint is available, use it */
+    bdrv_get_geometry(bs, &nb_sectors);
+    bdrv_get_geometry_hint(bs, &cylinders, &heads, &secs);
+    translation = bdrv_get_translation_hint(bs);
+    if (cylinders != 0) {
+        *pcyls = cylinders;
+        *pheads = heads;
+        *psecs = secs;
+    } else {
+        if (guess_disk_lchs(bs, &cylinders, &heads, &secs) == 0) {
+            if (heads > 16) {
+                /* if heads > 16, it means that a BIOS LBA
+                   translation was active, so the default
+                   hardware geometry is OK */
+                lba_detected = 1;
+                goto default_geometry;
+            } else {
+                *pcyls = cylinders;
+                *pheads = heads;
+                *psecs = secs;
+                /* disable any translation to be in sync with
+                   the logical geometry */
+                if (translation == BIOS_ATA_TRANSLATION_AUTO) {
+                    bdrv_set_translation_hint(bs,
+                                              BIOS_ATA_TRANSLATION_NONE);
+                }
+            }
+        } else {
+        default_geometry:
+            /* if no geometry, use a standard physical disk geometry */
+            cylinders = nb_sectors / (16 * 63);
+
+            if (cylinders > 16383)
+                cylinders = 16383;
+            else if (cylinders < 2)
+                cylinders = 2;
+            *pcyls = cylinders;
+            *pheads = 16;
+            *psecs = 63;
+            if ((lba_detected == 1) && (translation == BIOS_ATA_TRANSLATION_AUTO)) {
+                if ((*pcyls * *pheads) <= 131072) {
+                    bdrv_set_translation_hint(bs,
+                                              BIOS_ATA_TRANSLATION_LARGE);
+                } else {
+                    bdrv_set_translation_hint(bs,
+                                              BIOS_ATA_TRANSLATION_LBA);
+                }
+            }
+        }
+        bdrv_set_geometry_hint(bs, *pcyls, *pheads, *psecs);
+    }
+}
+
 void bdrv_set_geometry_hint(BlockDriverState *bs,
                             int cyls, int heads, int secs)
 {