Hi,
> At present, the interface program for Logger just performs a slightly > optimized brute force search for the Logger device driver. Although reliable, > it is very slow compared to providing a simple interrupt call to test for > installation. given that this detection will be done once per program start: how many microseconds do you expect to save? > Looking at the different interrupts, I think I have come up with a solution > that will work well for Logger and any other driver or program that needs > such a check. So, I’d like to propose a “standard” we could use. I’d like to > get your feedback on what I’m thinking… setting a "standard" which is used probably exactly once ? we write year 2023 ;) https://xkcd.com/927/ INT 2D has been mentioned by others > Looking at RBIL, interrupt 0x2b is barely used by anything. Under MS-DOS and > FreeDOS, this simply points to an IRET. Under IBM ROM-DOS, AH functions > 0x00-0x03 do some things. But, all other calls do nothing. > https://fd.lod.bz/rbil/interrup/dos_kernel/2b.html > <https://fd.lod.bz/rbil/interrup/dos_kernel/2b.html> > An install check issuing this interrupt would be simple to perform. A program > could set the Carry Flag, load AH/AX with “check for install” function and > set DS:BX to point to an identifier string (minimum 8 characters, no > maximum). Then call the interrupt. On return, if the Carry Flag is still set, > then the install check failed. If the Carry Flag is clear, it succeeded and > other register would be modified to according to the needs of the programs. > Implementation for Logger (as an example) could be: > > CHECK: > push cs > pop ds ; set DS to our code segment > stc ; set the carry flag > mov ax, 0xfd00 ; set AX to install check function > mov bx, LOGGER_ID ; offset to LOGGER device driver ID > int 0x2b ; call install check interrupt > jc NOT_INSTALLED ; nothing changed, driver is not > loaded ;you should add cmp ax, MAGIC_VALUE jne NOT_INSTALLED your proposed INT2B might be used by some other software that for some crazy reasons clears the carry flag. anyway, INT2D is probably the better choice anyway. _______________________________________________ Freedos-devel mailing list Freedos-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-devel
