Hello,
attached is a patch that modifies the block driver infrastructure to
support optional "dynamic" removable block devices. For example, today,
you can attach a CDROM block device, but it has to be manually attached
and ejected from the monitor, even if this block device points to a real
physical driver (i.e. /dev/cdrom on Linux), which itself supports really
removable media.
The patch does not change any current functionality. But, it can be
used to build a block driver which has dynamic state for the media, even
though the block device itself is attached statically. For example,
this will enable [in the future - new block driver needed] attaching a
real CDROM device, and having the ability to actually eject the media
and insert new media without having to use the monitor.
Regards,
Leo Reiter
--
Leonardo E. Reiter
Vice President of Product Development, CTO
Win4Lin, Inc.
Virtual Computing from Desktop to Data Center
Main: +1 512 339 7979
Fax: +1 512 532 6501
http://www.win4lin.com
Index: block.c
===================================================================
RCS file: /cvsroot/qemu/qemu/block.c,v
retrieving revision 1.25
diff -a -u -r1.25 block.c
--- block.c 18 Dec 2005 18:28:15 -0000 1.25
+++ block.c 16 Apr 2006 17:14:59 -0000
@@ -446,13 +446,21 @@
return 0;
}
+/* this function is needed to avoid checking for/calling dynamic methods for
+ * removable devices if the device is not designated as removable */
+static inline int bdrv_can_write(BlockDriverState *bs)
+{
+ if (!bs->removable)
+ return (bs->inserted) && (!bs->read_only);
+ else
+ return (bdrv_is_inserted(bs)) && (!bdrv_is_read_only(bs));
+}
+
/* return -1 if error */
int bdrv_write(BlockDriverState *bs, int64_t sector_num,
const uint8_t *buf, int nb_sectors)
{
- if (!bs->inserted)
- return -1;
- if (bs->read_only)
+ if (!bdrv_can_write(bs))
return -1;
if (sector_num == 0 && bs->boot_sector_enabled && nb_sectors > 0) {
memcpy(bs->boot_sector_data, buf, 512);
@@ -520,11 +528,15 @@
int bdrv_is_read_only(BlockDriverState *bs)
{
+ if (bs->drv && bs->drv->bdrv_is_read_only)
+ bs->read_only = bs->drv->bdrv_is_read_only(bs);
return bs->read_only;
}
int bdrv_is_inserted(BlockDriverState *bs)
{
+ if (bs->drv && bs->drv->bdrv_is_inserted)
+ bs->inserted = bs->drv->bdrv_is_inserted(bs);
return bs->inserted;
}
@@ -535,6 +547,13 @@
void bdrv_set_locked(BlockDriverState *bs, int locked)
{
+ /* XXX: bs->drv->bdrv_set_locked() has no need to set bs->locked; if this
+ * function gets called from the disk controller, it has to always set the
+ * locked state to whatever the disk controller says, regardless of whether
+ * or not this is implemented by the block driver itself or whether or not
+ * the block driver succeeds in setting the locked state. */
+ if (bs->drv && bs->drv->bdrv_set_locked)
+ bs->drv->bdrv_set_locked(bs, locked);
bs->locked = locked;
}
Index: block_int.h
===================================================================
RCS file: /cvsroot/qemu/qemu/block_int.h,v
retrieving revision 1.4
diff -a -u -r1.4 block_int.h
--- block_int.h 18 Dec 2005 18:28:15 -0000 1.4
+++ block_int.h 16 Apr 2006 17:14:59 -0000
@@ -40,6 +40,9 @@
int nb_sectors, int *pnum);
int (*bdrv_set_key)(BlockDriverState *bs, const char *key);
int (*bdrv_make_empty)(BlockDriverState *bs);
+ int (*bdrv_is_read_only)(BlockDriverState *bs);
+ int (*bdrv_is_inserted)(BlockDriverState *bs);
+ void (*bdrv_set_locked)(BlockDriverState *bs, int locked);
struct BlockDriver *next;
};
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