forums.ps2dev.org

[mik]

Hi,
I'm experimenting with interrupts using Jackson's ucLinux port and I'm asking me how did you find out that the hardware registers 0xbc300000 and 0xbc300010 are used to mask the interrupts (I'm referring to http://forums.ps2dev.org/viewtopic.php?t=7426&postdays=0&postorder=asc&start=90, crazyc's post)?

I'm trying to enable just UART1, which, I suppose, is the interrupt triggered by the joypad. I did some tests and got the following:

[J.F.]

The info on the int regs was derived from looking at the PSP's regular int handler code. If you're at all familiar with low-level coding of things like int handlers, it was fairly obvious what the registers were.

[mik]

I am unfamiliar with it and also pretty curious, thats why I'm asking :-)
You mean that it can be derived by looking only at the static assembly in sceKernelSuspendIntr for example or would it be needed to run pspinside on a 1.5 firmware?
Thx

[J.F.]

Just look over this. It has all the info for that needed... if you're ready for such low-level tasks. ;)

http://hitmen.c02.at/files/yapspd/psp_doc/chap9.html#sec9

[mik]

[J.F.]

Things like int handlers are the more complex parts of any kernel. It helps to have previous experience with such things on other computers. Many programmers start with 8 bit systems where ints are more simple, then move on to 16 bit systems which may have a simple controller, then work up to the full-blown int controllers found in modern PCs. Once you've worked on all that, the PSP int controller isn't too bad.

[mik]

[J.F.]

I learned by doing... the only books I read were language specifications. That's half the problem - I'm constantly pestered by kids asking how they can acquire my skills... in a month. They aren't happy when I tell them to spend 20 years programming. :D

[mik]

Well, maybe because its not a completely valid argument :-P
Today, due to the increasing complexity of technology, it is more difficult to get your feet on the ground than it was 20 years ago. On the other hand, today it's probably easier (and faster) to find the needed information, but the time and effort required to digest it, remained stable.

Back to the topic...
Since someone wise did already the hard job of reconstructing the data structures and logic flow of the int handler code, I thought I could learn from it by both looking at the assembly and at the pseudo code in the yapspd. I'm not only interested how this specific interrupt handler code works, but I'd like to acquire the knowledge to solve (in some distant future) such puzzles on my own.
Quick question: from which firmware is the code in yapspd reconstructed? The memory addresses don't match to the assembly I'm looking at (from owf 1.50).
Eg:

default_irq_handler(void) /* 88020F74 (interruptman:0x2274) */

is, I *suppose*

; Subroutine sub_00002224 - Address 0x00002224
sub_00002224:

in the assembly (I derived that from the context of both representations, but it would be much easier to understand whats going on, if I could compare and navigate by the addresses).
Thx

[jean]

[mik]

[J.F.]

If you can't make do with the uclinux port code, the thread mentioned above, and the yet another page linked above, you'll have to spell out what you're trying to do more clearly and succinctly.

BTW, in the yet another doc, code mentioned that isn't part of the listing isn't important - ignore calls to it. The part of the code someone would be interested in is all there.

[mik]

Ok, sorry if my request was not clear, I'll try to formulate it more explicitly.

I'd like to follow/read the code in http://hitmen.c02.at/files/yapspd/psp_doc/chap9.html#sec9.5.2 and trace it back to the assembly of firmware 1.5 I have.

I don't do this to understand the functionality of the code (for now), but to:
- retrain/refresh my rusty mips ;)
- learn how people do actually reverse engineering (I know it's not trivial, this example shows it...) and come up with the code as shown in yapspd

Simple as that... I know, I may trivialize, but this is due too my inexperience on this topic.

Edit: You may ask: "All this for using the interrupt controller? That's not needed!"
I know, but the journey is the goal ;) Gather experience, dig deep and discover what's behind the curtain.

[J.F.]

Well, the first step is to get the MIPS manuals and learn MIPS assembly. Otherwise it's hard to tell anything for the code. :D

[mik]