...It's a nightmare and I wonder why the CHDK standard is to go to play mode...
if your interested in a discussion about this, see here: http://chdk.setepontos.com/index.php/topic,3994.msg42107.html#msg42107
A patch as discussed there appears possible for S90
(from a quick peek at the trunk938 source)
For the moment, to boot straight to shooting mode,
press and hold try pressing and holding down ON/OFF
until you see the CHDK logo appear or hear the lense extend (~ 1 sec on my ixus 870is)
[edit: formulated more carefully - can't be sure if long press works on S90 ]
[edit2: added patch suggestion (untested, of course !) ]
To patch the boot behaviour, the following line needs to be changed in trunk938 from
*(int*)(0x254C)= (*(int*)0xC0220128)&1 ? 0x2000000 : 0x1000000; // replacement for correct power-on.
*(int*)(0x254C)= (*(int*)0xC0220128)&1 ? 0x1000000 : 0x2000000; // replacement for correct power-on.
the code is identical for all 3 firmware revisions, locations are as follows:
in platform/s90/sub/100c/boot.c -> line 134
in platform/s90/sub/101a/boot.c -> line 143
in platform/s90/sub/101c/boot.c -> line 131