On Mon, Mar 17, 2008 at 12:31 PM, Pavel Roskin <[EMAIL PROTECTED]> wrote: > On Sat, 2008-03-15 at 15:34 +0800, Bean wrote: > > > Ok, the new patch add (cd0) alias for cdrom device, the corresponding > > (hdN) is also present. > ... > > > (grub_biosdisk_call_hook): Only handle (hdN) device name. > > I still don't understand this part. Maybe you could split your patch > into smaller parts? > > Suppose we hard drives at 0x80 and 0x82 and a CD at 0x90. We can call > grub_biosdisk_get_cdinfo_int13_extension() and figure out that 0x90 is > the boot CD, so we call it (cd0). Then we go through the drives and > call them (hd0), (hd1). > > If it's OK to have an alias, why not suppress of hide the original name? > > At what point do we need to use the _name_ to calculate the BIOS number? > Why cannot we simply store that number into some field?
If we use (cd0) as primary name, there are three places where the cdrom has to been checked. 1. make_install_device in init.c. Here, given the boot drive number grub_boot_drive, we need to figure out the root device name. This is outside biosdisk, can't access device or disk. 2. grub_biosdisk_iterate in biosdisk.c We need to calculate all the disk names belong to this device, and call the hook. No parameter is passed. 3. grub_biosdisk_open in biosdisk.c Given a name, we need to figure out the bios number in order to initialize the disk parameter. 4. Some boot loader We need use the root variable to determine the bios number. The call order is as follows, make_install_device will always be called at init time, grub_biosdisk_open is called when we open a disk, and grub_biosdisk_iterate is called when we iterate disk using ls or search. The tricky part is how to make them all consistent. In order to do so, we have to detect cdrom and store the number as global variable somewhere. If we put it the kernel, it's workable, but it seems odd because this is clearly a biosdisk related function. If we put it in biosdisk, then kernel and boot loader would have to depend on biosdisk, then what if we want to use ata ? Also some thoughts about generic alias handling, it's not easy to implement. First, we need to decide where to create the alias. We can't create it in grub_biosdisk_open, the mapping should be made before calling grub_biosdisk_open. We can't create it in grub_biosdisk_iterate, as it's not necessary called before grub_biosdisk_open. It seems we can only do it in module initialization. But then, we need to iterate disks in order to find the cdrom, this somehow duplicate grub_biosdisk_iterate's job. Then, We also need to consider when to release the alias. -- Bean _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org http://lists.gnu.org/mailman/listinfo/grub-devel
