PCI Scan Shows no storage controllers

[Z3NT0N]

Hi, I am having an issue where i do a pci scan(brute force). But i don't seem to find any storage devices/controllers.
When i use command -> lspci -vv <- in the linux "konsole".
From reading the devices that it has recognised, it shows that it detected a SATA controller on a
ISA bridge on function 2 of bus 0 device 0x1F.

But when i read the ISA bridge header common variables on function 0. The header type is 0x8D and from what i
have read in the PCI link on the Main Page there should be 3 types(0x80/0x81/0x82). Also when i read function 2
the common variables are all 0.

I have tested on both qemu and my own hardware and shows no storage controllers(class 0x01) even though i ignore the subclass.

So i am unsure how Linux detected this.
Any advice on how i should move forward would be appreciated.

[Octocontrabass]

It sounds like your code to read the PCI configuration space doesn't work properly. The header type is not 0x8D, and function 2 should have nonzero values in its configuration space.

[Z3NT0N]

Hi Octocontrabass, you were right i had some bugs in my code when bit shifting the function number into the register before using the out command and it resulted in reading function 0 with a masked offset:

faulty code:

; ecx is the device count --- ebx is the bus count --- edi is the offset --- edx is the function number
_PCIRead: xor eax,eax

or edi,0x80000000
and edi,0x800000FC
or al,bl
shl eax,8
shl ecx,3
or al,cl
shr ecx,3
shl eax,5
or al,dl ; this line is supposed to exchange positions with the line above it and then i can merge the two shl commands to shl eax,8
shl eax,3
or eax,edi
mov dx,0xCF8
out dx,eax
mov dx,0xCFC
in eax,dx
ret

I should have tested more thoroughly, I'm sorry.
This is my first topic. Do i close the topic or do the moderators?

[Octocontrabass]

There's no need to close the topic.

Is there any particular reason why you chose to write this function in assembly? It's much easier to catch mistakes in higher-level languages.

[Z3NT0N]

Even though this is my first time working through OS development, i am trying to do the whole thing(my software idea not a full OS) in assembly. I did try to look at how i could use c but was not sure how to set the origin point of the code as you can do in an assembler like nasm([org 0x7C00]). I am more interested in assembly anyway so i just gave up on c. Its a little crazy to do it in assembly but i am enjoying it so far.

[Octocontrabass]

I did try to look at how i could use c but was not sure how to set the origin point of the code as you can do in an assembler like nasm([org 0x7C00]).

You can do that using a linker script. You probably wouldn't want to write a boot sector in C, though.

[Z3NT0N]

The way i have been doing it so far is that I have been writing the code in "kate" on linux haha and then i assemble each file ("nasm -f bin name.asm -o name.img"), I have one file for the bootloader, one for the protected mode switch and then a third for my main code that runs after the PE switch. I then combine the binary outputs and then boot from that, its quite messy but seems to be working. Thank you for the link, I will have a look.