diff --git a/kernel/trunk/core/exports.inc b/kernel/trunk/core/exports.inc
index 278e36565b..8bf11681df 100644
--- a/kernel/trunk/core/exports.inc
+++ b/kernel/trunk/core/exports.inc
@@ -85,6 +85,10 @@ iglobal
   szStrchr            db 'strchr',0
   szStrrchr           db 'strrchr',0
 
+  szDiskAdd           db 'DiskAdd',0
+  szDiskDel           db 'DiskDel',0
+  szDiskMediaChanged  db 'DiskMediaChanged',0
+
 
 align 16
 kernel_export:
@@ -160,6 +164,10 @@ kernel_export:
   dd szStrchr          , strchr
   dd szStrrchr         , strrchr
 
+  dd szDiskAdd         , disk_add
+  dd szDiskDel         , disk_del
+  dd szDiskMediaChanged, disk_media_changed
+
 exp_lfb:
   dd szLFBAddress      , 0
   dd 0                      ;terminator, must be zero
diff --git a/kernel/trunk/docs/drivers_api.txt b/kernel/trunk/docs/drivers_api.txt
new file mode 100644
index 0000000000..9c71a1e420
--- /dev/null
+++ b/kernel/trunk/docs/drivers_api.txt
@@ -0,0 +1,75 @@
+All functions are stdcall unless mentioned otherwise.
+
+=== Disk ===
+The kernel exports the functions 'DiskAdd', 'DiskMediaChanged', 'DiskDel' for
+drivers. They must be called in the following order: DiskAdd, then zero or
+more DiskMediaChanged, then optionally DiskDel. The driver must not call
+two functions in parallel, including two calls to DiskMediaChanged.
+
+void* DiskAdd(DISKFUNC* functions, const char* name, void* userdata, int flags);
+; The pointer 'functions' must be valid at least until the disk will be deleted
+; (until DISKFUNC.close is called).
+; The pointer 'name' can be invalid after this function returns.
+; It should point to ASCIIZ-string without leading '/' in latin lowercase and
+; digits, like 'usbhd0'.
+; The value 'userdata' is any pointer-sized data, passed as is to all
+; callbacks.
+DISK_NO_INSERT_NOTIFICATION = 1
+; The bitfield 'flags' has currently only one bit defined. If it is set, the
+; driver will never call DiskMediaChanged(hDisk, true), so the kernel must scan
+; for media insertion when the operation is requested.
+struc DISKFUNC
+{
+  .strucsize  dd ?
+  .close      dd ?
+; void close(void* userdata);
+; Optional.
+; The last function that is called for the given disk. The kernel calls it when
+; the kernel has finished all operations with the disk and it is safe to free
+; all driver-specific data identified by 'userdata'.
+  .closemedia dd ?
+; void closemedia(void* userdata);
+; Optional.
+; The kernel calls this function when it finished all processing with the
+; current media. If media is removed, the driver should decline all requests
+; to that media with DISK_STATUS_NO_MEDIA, even if new media is inserted,
+; until this function is called. If media is removed, a new call to
+; DiskMediaChanged(hDisk, true) is not allowed until this function is called.
+  .querymedia dd ?
+; int querymedia(void* userdata, DISKMEDIAINFO* info);
+; return value: 0 = success, otherwise = error
+  .read       dd ?
+; int read(void* userdata, void* buffer, __int64 startsector,
+;          int* numsectors);
+; return value: 0 = success, otherwise = error
+  .write      dd ?
+; int write(void* userdata, const void* buffer, __int64 startsector,
+;           int* numsectors);
+; Optional.
+; return value: 0 = success, otherwise = error
+  .flush      dd ?
+; int flush(void* userdata);
+; Optional.
+; Flushes the hardware cache, if it exists. Note that a driver should not
+; implement a software cache for read/write, since they are called from the
+; kernel cache manager.
+}
+struc DISKMEDIAINFO
+{
+  .flags      dd ?
+DISK_MEDIA_READONLY = 1
+  .sectorsize dd ?
+  .capacity   dq ?
+}
+void DiskDel(void* hDisk);
+; This function informs the kernel that the disk should be deleted from the
+; system. This function removes the disk from the global file system; however,
+; it is possible that active operations with the disk are still running. When
+; the disk is actually removed, the kernel calls the 'close' function, which
+; can free all device-related resources.
+void DiskMediaChanged(void* hDisk, int newstate);
+; This function informs the kernel that a media has been inserted, removed or
+; changed. 'newstate' should be zero if currently there is no media inserted
+; and nonzero in the other case. This function must not be called with nonzero
+; 'newstate' from any of callbacks. This function must not be called if another
+; call to this function is active.
diff --git a/kernel/trunk/fs/disk.inc b/kernel/trunk/fs/disk.inc
index 39cce17be5..4a57c7e9be 100644
--- a/kernel/trunk/fs/disk.inc
+++ b/kernel/trunk/fs/disk.inc
@@ -633,10 +633,12 @@ lock    dec     [partition_buffer_users]        ; no, we must allocate
 ; Note that 'read' callback operates with 64-bit sector numbers, so we must
 ; push additional zero as a high dword of sector number.
         mov     al, DISKFUNC.read
-        stdcall disk_call_driver, ebx, ebp, 0, 1
+        push    1
+        stdcall disk_call_driver, ebx, ebp, 0, esp
+        pop     ecx
 ; 6. If the read has failed, abort the loop.
-        test    eax, eax
-        jz      .mbr_failed
+        dec     ecx
+        jnz     .mbr_failed
 ; 7. Check the MBR/EBR signature. If it is wrong, abort the loop.
 ; Soon we will access the partition table which starts at ebx+0x1BE,
 ; so we can fill its address right now. If we do it now, then the addressing