hard disk dirver

[Valdis.Kletnieks at vt.edu]

On Wed, 06 Feb 2013 02:53:11 +0800, horseriver said:
>   At booting time ,bootloader loads kernel from hard disk too memory.
>   During this period,does it need hd driver's support .

Think for a bit - at that point, the hd driver hasn't been loaded
yet, so it *can't* need the hd driver's support.  So instead, the
bootloader has a very dumb simplistic driver that's stripped down
(for instance, no queued command support, one I/O in flight at a
time, very little error handling, read operations only , etc etc)
that's just enough to load the kernel and initrd. (There's often
also a very stupid filesystem driver, just enough to read files.
So for instance 'grub' can find the files for the kernel and initrd.
Some bootloaders are too stupid for even that, and you have to
run a special program to tell the boot loader where all the blocks
of the file are (I'm looking at you, LILO :)

Once the bootloader gets the kernel and initrd loaded, *then* the
kernel can initialize the production driver with all the bells and
whistles needed.
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