On Thu, Apr 25, 2013 at 02:14:59PM -0700, Tejun Heo wrote:
> Hello,
[...]
> >
> > Right now, if you add a new block driver, if you want grub to be able
> > to boot it, you also have to modify grub. This is true for each new
> > block driver that comes along. This is not the case for SCSI HBA
> > drivers, because they all get to share the sd driver and its device
> > name space, and grub already knows about that. You can add all kinds
> > of SCSI HBA drivers and never have to worry about needing to modify
> > grub to get boot support.
>
> So, the question, I suppose, is why grub needs to be changed when the
> stem of device names changes. Why does it need to do that? Is it
> just an implementation detail or is it something more fundamental?
>
I don't know. I do know that it looks like a lot of the the various block
device name schemes are more or less hard coded into grub with bits of code
like this:
static void
get_ide_disk_name (char *name, int unit)
{
#if defined(__linux__)
/* GNU/Linux */
sprintf (name, "/dev/hd%c", unit + 'a');
#elif defined(__GNU__)
/* GNU/Hurd */
sprintf (name, "/dev/hd%d", unit);
#elif defined(__FreeBSD_kernel__)
[...]
static void
get_scsi_disk_name (char *name, int unit)
{
#if defined(__linux__)
/* GNU/Linux */
sprintf (name, "/dev/sd%c", unit + 'a');
#elif defined(__GNU__)
/* GNU/Hurd */
sprintf (name, "/dev/sd%d", unit);
#elif defined(__FreeBSD_kernel__)
there are about 9 different get_blah_disk_name() type functions in there
for the various device naming schemes.
It looks like these are called from a function called init_device_map()
that is called from grub_stage2() at least in the version of grub I looked
at (0.97, from rhel6).
So my assumption is that adding a new block driver with yet another name space
would require adding another bit of code into grub like those above. When I
asked about "best practices" for new block driver device names on the grub devel
mailing list to minimize required changes to grub, nobody argued against that
assumption.
-- steve
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