[Geekos-devel] Re: IDE driver details

[David H. <da...@cs...>]

Hi Vishal,

On Tue, Jan 29, 2002 at 04:41:19AM -0800, Vishal Soni wrote:
> Hi Dave,
> 
> As ATA 1 standard specifies there are two modes of operation
> 1. CHS-Cylinder Head Sector
> 2. LBA-Logical Block Access (Drive is treated as logical array of
> 512byte         	blocks)
> 
> Which of the following modes u are planning to use for Virtual Memory
> implementation??
> 
> This is necessary for me to make a C interface for the Kernel for
> access.

I think LBA mode would be a lot nicer to deal with than CHS.
Maybe the driver could emulate LBA for drives/controllers that don't support
LBA, so that the kernel API for all block devices was LBA.

I must admit I really don't know a lot about hard drives (or
operating systems :-), so I may not be aware of all of the issues.

> We could possibly have a driver that would allow us to use LBA and CHS
> mode. I am not sure what modes drives operate in VM systems, ff you have
> some idea let me know.

I don't think whether or not virtual memory is in use makes a
difference, unless you're using DMA (which I think needs physical
addresses).

Just to double-check: you're working with the experimental
version of GeekOS?  http://geekos.sourceforge.net/experimental.html
All new development will be on that version.

> Write now I have modified the kernel boot up code to get some drive
> parameters from BIOS Hard Disk drive parameter table. This information
> is propagated to the Main() function.

Good.  Did you add new fields to the boot_info struct?

> I have most of the stuff for ATA-1
> driver figured out. The interface C code I am planning to add to the
> kernel right now would have some basic functionality of 
> 1. Initializing drives
> 2. Read sectors/blocks
> 3. Write sectors/blocks
> 4. Querying drive information
> 5. Seek
> 
> and some other commands.
> 
> I am not planning to use DMA or interrupts for this initial version of
> driver. So it will be strictly Programmed I/0 achieved by communicating
> at IN/OUT ports

This all sounds great!  Let me know if you have any other questions.
Also, feel free to send email to the geekos-devel mailing list,
that way everyone working on geekos will know what you're doing.

-Dave