Reading ATA status port always gives 0xFF (IDENTIFY command)

[Cyao]

Hello,

Im tring to read from my boot cdrom, but its always responding 0xFF , and I've checked and i think that all the logic is right, can anyone help me have a look? thanks!

https://github.com/cheyao/AchiveOS/blob ... b/cd.c#L33

[Octocontrabass]

Does your virtual machine's debug log show that you're accessing the hardware? Bochs is very talkative if you enable debug messages.

[Cyao]

Does your virtual machine's debug log show that you're accessing the hardware? Bochs is very talkative if you enable debug messages.

Nope, no messages after the 00035981151i[BIOS ] Booting from 07c0:0000 message

[nullplan]

0xFF is the open bus value. You seem to think it was 0, but no, if no hardware is there, you get all 1-bits. Unfortunately, for some hardware ports, 0xFF is also a valid register value. Anyway, you do not seem to be detecting ATA, but are just assuming an ATA controller to be at a predetermined address.

0xFF being the open-bus value is also why most A20 enabling code using the keyboard controller is wrong on systems that don't have a keyboard controller. But that is a question for another time.

[Cyao]

0xFF is the open bus value. You seem to think it was 0, but no, if no hardware is there, you get all 1-bits. Unfortunately, for some hardware ports, 0xFF is also a valid register value. Anyway, you do not seem to be detecting ATA, but are just assuming an ATA controller to be at a predetermined address.

0xFF being the open-bus value is also why most A20 enabling code using the keyboard controller is wrong on systems that don't have a keyboard controller. But that is a question for another time.

I think that shouldn't be the case, it reports 0xff for all 4 ports, but atleast one should have something since i've got a cdrom connected

[Cyao]

And now I just used changed it to use a pointer, but now it gets 0 out of the pointer when using -O2, but -O1 and -O0 works. Is there some kind of UB that im overlooking?

[Octocontrabass]

How big is your kernel binary?

[Cyao]

How big is your kernel binary?

Its only 19 sectors, enough for now.

And I found the problem, some how i needed a delay after the inb, dunno why, but its fixed

but thanks for the help!

[Octocontrabass]

Its only 19 sectors, enough for now.

Are you sure? I checked a recently-generated disk image and the kernel binary in that one is at least 30 sectors...

[Cyao]

Its only 19 sectors, enough for now.

Are you sure? I checked a recently-generated disk image and the kernel binary in that one is at least 30 sectors...

That's weird, on my pc it's only 19 sectors, anywas im going to increase it a little bit

[Octocontrabass]

You should figure out a way to automatically load the correct number of sectors. Otherwise, you'll keep running into problems whenever your kernel outgrows your bootloader.