blockdev: make selection structure opaque

I'm about to change that structure and I don't want fs to be messed up
by this. I'm proceeding step by step...

doc/glue-code.md

@@ -26,7 +26,7 @@ look like:
         im 1
         call aciaInit
         xor	a
-        ld	de, BLOCKDEV_GETC
+        ld	de, BLOCKDEV_SEL
         call	blkSel
         call	stdioInit
         call    shellInit

kernel/blockdev.asm

@@ -59,15 +59,12 @@
 ; Pointer to the selected block device. A block device is a 8 bytes block of
 ; memory with pointers to GetC, PutC, Seek and Tell routines, in that order.
 ; 0 means unsupported.
-.equ	BLOCKDEV_GETC		BLOCKDEV_RAMSTART
-.equ	BLOCKDEV_PUTC		BLOCKDEV_GETC+2
-.equ	BLOCKDEV_SEEK		BLOCKDEV_PUTC+2
-.equ	BLOCKDEV_TELL		BLOCKDEV_SEEK+2
-.equ	BLOCKDEV_RAMEND		BLOCKDEV_TELL+2
+.equ	BLOCKDEV_SEL		BLOCKDEV_RAMSTART
+.equ	BLOCKDEV_RAMEND		BLOCKDEV_SEL+8
 
 ; *** CODE ***
 ; Select block index specified in A and place them in routine pointers at (DE).
-; For example, for a "regular" blkSel, you will want to set DE to BLOCKDEV_GETC.
+; For example, for a "regular" blkSel, you will want to set DE to BLOCKDEV_SEL.
 blkSel:
 	push	af
 	push	de
@@ -120,13 +117,13 @@ blkSel:
 ; Sets Z according to whether read was successful: Set if successful, unset
 ; if not.
 blkGetC:
-	ld	ix, (BLOCKDEV_GETC)
+	ld	ix, (BLOCKDEV_SEL)
 	jp	(ix)
 
 ; Reads B chars from blkGetC and copy them in (HL).
 ; Sets Z if successful, unset Z if there was an error.
 blkRead:
-	ld	ix, (BLOCKDEV_GETC)
+	ld	ix, (BLOCKDEV_SEL)
 _blkRead:
 	push	hl
 	push	bc
@@ -145,16 +142,20 @@ _blkRead:
 ; Writes character in A in current position in the selected device. Sets Z
 ; according to whether the operation was successful.
 blkPutC:
-	ld	ix, (BLOCKDEV_PUTC)
+	ld	ix, (BLOCKDEV_SEL+2)
 	jp	(ix)
 
 ; Writes B chars to blkPutC from (HL).
 ; Sets Z if successful, unset Z if there was an error.
 blkWrite:
-	ld	ix, (BLOCKDEV_PUTC)
+	ld	ix, (BLOCKDEV_SEL)
 _blkWrite:
+	push	ix
 	push	hl
 	push	bc
+	; make IX point to PutC
+	inc	ix
+	inc	ix
 .loop:
 	ld	a, (hl)
 	call	callIX
@@ -165,6 +166,7 @@ _blkWrite:
 .end:
 	pop	bc
 	pop	hl
+	pop	ix
 	ret
 
 ; Seeks the block device in one of 5 modes, which is the A argument:
@@ -184,8 +186,8 @@ _blkWrite:
 ; If the device is "growable", it's possible that seeking to end when calling
 ; PutC doesn't necessarily result in a failure.
 blkSeek:
-	ld	ix, (BLOCKDEV_SEEK)
-	ld	iy, (BLOCKDEV_TELL)
+	ld	ix, (BLOCKDEV_SEL+4)
+	ld	iy, (BLOCKDEV_SEL+6)
 _blkSeek:
 	; we preserve DE so that it's possible to call blkSeek in mode != 0
 	; while not discarding our current DE value.
@@ -234,7 +236,7 @@ _blkSeek:
 ; Returns the current position of the selected device in HL (low) and DE (high).
 blkTell:
 	ld	de, 0			; in case device ignores DE.
-	ld	ix, (BLOCKDEV_TELL)
+	ld	ix, (BLOCKDEV_SEL+6)
 	jp	(ix)
 
 ; This label is at the end of the file on purpose: the glue file should include

kernel/blockdev_cmds.asm

@@ -8,7 +8,7 @@ blkBselCmd:
 	cp	BLOCKDEV_COUNT
 	jr	nc, .error	; if selection >= device count, error
 	push	de
-	ld	de, BLOCKDEV_GETC
+	ld	de, BLOCKDEV_SEL
 	call	blkSel
 	pop	de
 	xor	a

kernel/fs.asm

@@ -369,7 +369,7 @@ fsblkPutC:
 
 fsblkWrite:
 	push	ix
-	ld	ix, (FS_PUTC)
+	ld	ix, (FS_GETC)	 ; we have to point to blkdev's beginning
 	call	_blkWrite
 	pop	ix
 	ret
@@ -523,7 +523,7 @@ fsOn:
 	push	bc
 	; We have to set blkdev routines early before knowing whether the
 	; mounting succeeds because methods like fsReadMeta uses fsblk* methods.
-	ld	hl, BLOCKDEV_GETC
+	ld	hl, BLOCKDEV_SEL
 	ld	de, FS_GETC
 	ld	bc, 8		; we have 8 bytes to copy
 	ldir			; copy!

recipes/rc2014/sdcard/glue.asm

@@ -72,7 +72,7 @@ init:
 	ld	(SHELL_CMDHOOK), hl
 
 	xor	a
-	ld	de, BLOCKDEV_GETC
+	ld	de, BLOCKDEV_SEL
 	call	blkSel
 
 	ei

recipes/rc2014/zasm/glue.asm

@@ -99,7 +99,7 @@ init:
 	ld	(SHELL_CMDHOOK), hl
 
 	xor	a
-	ld	de, BLOCKDEV_GETC
+	ld	de, BLOCKDEV_SEL
 	call	blkSel
 
 	ei

tools/emul/shell/shell_.asm

@@ -47,7 +47,6 @@
 .dw	stdinGetC, stdinPutC, stdinSeek, stdinTell
 .dw	mmapGetC, mmapPutC, mmapSeek, mmapTell
 
-#include "blockdev_cmds.asm"
 
 .equ	MMAP_RAMSTART	BLOCKDEV_RAMEND
 .equ	MMAP_START	0xe000
@@ -59,7 +58,6 @@
 .equ	FS_RAMSTART	STDIO_RAMEND
 .equ	FS_HANDLE_COUNT	2
 #include "fs.asm"
-#include "fs_cmds.asm"
 
 .equ	SHELL_RAMSTART		FS_RAMEND
 .equ	SHELL_EXTRA_CMD_COUNT	9
@@ -67,11 +65,14 @@
 .dw	blkBselCmd, blkSeekCmd, blkLoadCmd, blkSaveCmd
 .dw	fsOnCmd, flsCmd, fnewCmd, fdelCmd, fopnCmd
 
+#include "blockdev_cmds.asm"
+#include "fs_cmds.asm"
+
 .equ	PGM_RAMSTART		SHELL_RAMEND
 .equ	PGM_CODEADDR		USERCODE
 #include "pgm.asm"
 
-.out	PGM_RAMEND
+;.out	PGM_RAMEND
 
 init:
 	di
@@ -84,7 +85,7 @@ init:
 	call	mmapInit
 	call	fsInit
 	ld	a, 0	; select fsdev
-	ld	de, BLOCKDEV_GETC
+	ld	de, BLOCKDEV_SEL
 	call	blkSel
 	call	fsOn
 	call	shellInit

tools/emul/zasm/glue.asm

@@ -49,7 +49,7 @@ init:
 	ld	hl, 0xffff
 	ld	sp, hl
 	ld	a, 2	; select fsdev
-	ld	de, BLOCKDEV_GETC
+	ld	de, BLOCKDEV_SEL
 	call	blkSel
 	call	fsOn
 	ld	hl, .zasmArgs