How to start?

[eddyb]

Hi!
I'm a newbie in os developing. I want to learn more about it, before to start to develop a small os.
I know some C, C++, a little asm. What do you recomend for a beginer? Bran's Kernel Development Tutorial it's good to start with? What is the order that should I do the things?(there is a page on wiki about this, but is not complete)
Thanks!

[JamesM]

There is a page on the wiki about it, and it is complete enough. There are also at least 2 open threads on the first page of this subforum which ask this exact same question. Please read those first.

[eddyb]

Hi!
I made my first build. I used only ASM, no C files. No boot problem.

Version 0.0.0.1. Succesfully booting.

I aded this code after the start of the kernel:

Code: Select all

	mov AH, 0x7A
	mov AL, 'H'
	mov [0xB8640], AX
	mov AL, 'e'
	mov [0xB8642], AX
	mov AL, 'l'
	mov [0xB8644], AX
	mov AL, 'l'
	mov [0xB8646], AX
	mov AL, 'o'
	mov [0xB8648], AX
	mov AL, ' '
	mov [0xB864A], AX
	mov AL, 'W'
	mov [0xB864C], AX
	mov AL, 'o'
	mov [0xB864E], AX
	mov AL, 'r'
	mov [0xB8650], AX
	mov AL, 'l'
	mov [0xB8652], AX
	mov AL, 'd'
	mov [0xB8654], AX
	mov AL, '!'
	mov [0xB8656], AX

And then I got a nice green on grey "Hello World!".

Version 0.0.0.2. Nice "Hello World!";).

What is the next point? Is good to follow Bran's Kernel Development Tutorial?
Or i need to do something else?
PS: I atached some screenshots

[Adek336]

Nice

Tutorials are great to follow, they give you some insight. The next step now would be reading old posts in this forum - there have been a few discussions about the order of implementation.

[eddyb]

I followed the Bran's tut, and i have all modules.
What i must do next? write more drivers?
or is better to use graphics and develop a gui?
Thanks
PS: I have more screenshots... If you want, i'll post them

[Adek336]

If they print out something more than what the tutorial says then sure post 'em this ya thread Have you read the recent threads about starting an os?

[codemastersnake]

you can also check my wiki if you want to!

[eddyb]

Snake, your wiki is very tricky. I can't get to any page.
I've understood that i must have memory manager and multi-tasking before loadin programs from hardisk, and having gui.
I'll play a little with drivers, I want make some drivers, so i don't need to make them later.

[AJ]

I followed the Bran's tut, and i have all modules.
What i must do next?

Hi,

I know it's a good feeling when you get a kernel working for the first time, but the secret now is not to rush. Bran's tutorial is good for teaching you the basics, but is not so good to use as the base of your own OS.

I think that the next stage should be one of design and reading. What do you want to get out of OS dev? Do you have a target audience (or, like me, do you just develop for the enjoyment?). How do you want drivers to interface to the kernel? Do you want a monolithic or microkernel? How do you want user apps to interface with the kernel?

While the GUI is an important part of the design process, it should not be the next thing you implement (perhaps try a decent memory manager first).

Cheers,
Adam

[eddyb]

I want my kernel to be a monolithic one. It has all drivers in it, and after start, it gives control to a text or graphic interface.
I think it's the way linux works.
So, I need to work on drivers(i've got only keyb, timer, and textscreen)-what are the most neccesary?

[eddyb]

I'm working on pci driver. If someone can explain to me how BAR and other pci stuff works, is welcome.
And I have a problem with VS2008: why in the output of build there is only echo output ? I'm reffering at the NMake tool, for using my own build script. I can't see gcc, or linker output. i haven't this problem in the past...

[AJ]

I'm working on pci driver. If someone can explain to me how BAR and other pci stuff works, is welcome.

Have a look at PCI.

Cheers,
Adam

[eddyb]

i've readed it already, but is a little confuzing.
my pci driver goes mad... the scan does't show any detected message and at the end it says that found 0 devices...
Can be from VMWare? some sort of pci disabled?

[Adek336]

(I think a base address register's lowest bit means if it is IO space address)
So you read the class and subclasses codes for all the buses and slots, right? And all of them are 0?
Vmware can't have PCI disabled.

[eddyb]

i read the vendor's id, and skip device if is 0xFFFF.
here is the code:

Code: Select all

int pci_read(int bus, int dev, int func, int reg)
{
  outportl(0xCF8, ((unsigned long) 0x80000000 | (bus << 16) | (dev << 11) | (func << 8) | reg));
  return inportl(0xCFC);
}

PCI_Device_t* pci_readdevice(int bus, int dev, int func)
{
	PCI_Device_t* ret;
	ret->VendorID      =   (short) (pci_read(bus,dev,func,0)&0x0000FFFF);
	ret->DeviceID      =   (short)((pci_read(bus,dev,func,0)&0xFFFF0000) >> 16);
	ret->CommandReg    =   (short) (pci_read(bus,dev,func,4)&0x0000FFFF);
	ret->StatusReg     =   (short)((pci_read(bus,dev,func,4)&0xFFFF0000) >> 16);
	ret->RevisionID    =   (short) (pci_read(bus,dev,func,8)&0x0000FFFF);
	ret->SubClass      =   (char) ((pci_read(bus,dev,func,8)&0x00FF0000) >> 16);
	ret->ClassCode     =   (char) ((pci_read(bus,dev,func,8)&0xFF000000) >> 24);
	ret->CachelineSize =   (char)  (pci_read(bus,dev,func,12)&0x000000FF);
	ret->Latency       =   (char) ((pci_read(bus,dev,func,12)&0x0000FF00) >> 8);
	ret->HeaderType    =   (char) ((pci_read(bus,dev,func,12)&0x00FF0000) >> 16);
	ret->BIST          =   (char) ((pci_read(bus,dev,func,12)&0xFF000000) >> 24);
	ret->BAR0          =    pci_read(bus, dev, func, 16);
	ret->BAR1          =    pci_read(bus, dev, func, 20);
	ret->BAR2          =    pci_read(bus, dev, func, 24);
	ret->BAR3          =    pci_read(bus, dev, func, 28);
	ret->BAR4          =    pci_read(bus, dev, func, 32);
	ret->BAR5          =    pci_read(bus, dev, func, 36);
	ret->CardbusCISPtr =    pci_read(bus, dev, func, 40);
	ret->SubVendorID   =   (short) (pci_read(bus,dev,func,44)&0x0000FFFF);
	ret->SubDeviceID   =   (short)((pci_read(bus,dev,func,44)&0xFFFF0000) >> 16);
	ret->ExRomAddress  =    pci_read(bus, dev, func, 48);
	ret->Reserved1     =    pci_read(bus, dev, func, 52);
	ret->Reserved2     =    pci_read(bus, dev, func, 56);
	ret->IRQ           =   (char)  (pci_read(bus,dev,func,60)&0x000000FF);
	ret->PIN           =   (char) ((pci_read(bus,dev,func,60)&0x0000FF00) >> 8);
	ret->MinGrant      =   (char) ((pci_read(bus,dev,func,60)&0x00FF0000) >> 16);
	ret->MaxLatency    =   (char) ((pci_read(bus,dev,func,60)&0xFF000000) >> 24);
	return ret;
}
void scanpci()
{
	int bus, dev, func, i;
	i=0;
	PCI_Device_t* device;
	printf("PCI Scan...\n");
	for (bus = 0; bus < 255; bus++)
	{
		putch('-');
		for (dev = 0; dev < 32; dev++)
		{
			for (func = 0; func < 8; func++)
			{
				device = pci_readdevice(bus, dev, func);
				if(device->VendorID != 0xFFFF)
				{
					i++;
					printf("\n--bus %u|device %u|function %u|has Vendor ID = 0x%x and Device ID = 0x%x", bus, dev, func, device->VendorID, device->DeviceID);
				}
				//else
					//printf("\n--bus %u | device %u | function %u | is null", bus, dev, func);
			}
		}
	}
	printf("Scan complete! %u devices found!", i);

}