diskio f_seek_w() abandoned due to unreliability

compiler/res/prog8lib/cx16/diskio.p8

@@ -693,15 +693,16 @@ internal_vload:
         cbm.CLOSE(15)
     }
 
-    ; TODO see if we can get this to work as well:
+
+    ; NOTE: f_seek_w() doesn't work reliably right now. I only manage to corrupt the fat32 filesystem on the sdcard with it...
 ;    sub f_seek_w(uword pos_hiword, uword pos_loword) {
 ;        ; -- seek in the output file opened with f_open_w, to the given 32-bits position
-;        f_seek.command[1] = 13       ; f_open_w uses channel 13
-;        f_seek.command[2] = lsb(pos_loword)
-;        f_seek.command[3] = msb(pos_loword)
-;        f_seek.command[4] = lsb(pos_hiword)
-;        f_seek.command[5] = msb(pos_hiword)
-;        goto f_seek.send_command
+;        diskio.f_seek.command[1] = 13       ; f_open_w uses channel 13
+;        diskio.f_seek.command[2] = lsb(pos_loword)
+;        diskio.f_seek.command[3] = msb(pos_loword)
+;        diskio.f_seek.command[4] = lsb(pos_hiword)
+;        diskio.f_seek.command[5] = msb(pos_hiword)
+;        goto diskio.f_seek.send_command
 ;    }
 
 }

docs/source/todo.rst

@@ -11,7 +11,6 @@ For 9.0 major changes
 - DONE: cx16diskio module merged into diskio (which got specialized for commander x16 target). load() and load_raw() with extra ram bank parameter are gone.
 - DONE: drivenumber parameter removed from all routines in diskio module. The drive to work on is now simply stored as a diskio.drivenumber variable, which defaults to 8.
 
-- get f_seek_w working like in the BASIC program on the sdcard - this needs the changes to diskio.f_open to use suffixes ,p,m
 - 6502 codegen: see if we can let for loops skip the loop if startvar>endvar, without adding a lot of code size/duplicating the loop condition.
   It is documented behavior to now loop 'around' $00 but it's too easy to forget about!
   Lot of work because of so many special cases in ForLoopsAsmgen.....

examples/cx16/fileseek.p8

@@ -31,9 +31,9 @@ main {
 
         read_last_bytes()
 
-; NOTE: f_seek_w() doesn't work right now. It requires substantial changes to the diskio library that are not compatible with the C64/C128.
+        ; NOTE: f_seek_w() doesn't work reliably right now. I only manage to corrupt the fat32 filesystem on the sdcard with it...
 ;        txt.print("\nseeking to 1292 and writing a few bytes...\n")
-;        if diskio.f_open_w("seektestfile.bin,p,m") {
+;        if diskio.f_open_w("seektestfile.bin,p,a") {
 ;            diskio.f_seek_w(0, 1292)
 ;            void diskio.f_write("123", 3)
 ;            diskio.f_close_w()
@@ -42,8 +42,8 @@ main {
 ;            txt.print(diskio.status())
 ;            sys.exit(1)
 ;        }
-;
-;        read_last_bytes()
+
+        read_last_bytes()
     }
 
     sub read_last_bytes() {