Re: [PATCH] Ensure boot CD can be accessed

[Christian Franke <Christian.Franke@t-online.de>]

Bean wrote:
> On Sat, Feb 16, 2008 at 5:13 AM, Christian Franke
> <...> wrote:
>   
>> ...
>>  Further testing outdated this patch. The boot CD appeared under the
>>  following drive numbers:
>>
>>  0x82 (old Toshiba Laptop with unknown BIOS)
>>  0x9f (PC with Phoenix-Award BIOS, VMware)
>>  0xe0 (VirtualBox)
>>  0xef (PC with AMI BIOS, VirtualPC)
>>
>>  Current CVS would only work for 0xe0, with the previous patch it works
>>  for all >= 0x9f.
>>
>>  This new patch also handles the case that the CD appears under the
>>  legacy controller drive number (0x82 = secondary master). It is accessed
>>  as "hd2" in this case.
>>
>>  Christian
>>
>>  ...
>>     
>
> I'm thinking, is there a more generic way to test for cd drive ? also,
> if the cd drive can appear as (hd2), maybe we can use (hdx) for other
> cases as well, such as (hd96), etc. The name might be a little
> strange, but we can get the bios drive number quite easily, which can
> be useful sometimes (some boot loader need to know the boot drive
> number).
>
>   

Good point.

Besides the heuristics "(boot drive >= 0x9f) => (likely a boot CD)", 
there is apparently no clean method to distinguish CD from HDD on the 
legacy BIOS call level.

Is the special handling for CD in grub_biosdisk_rw() necessary, or can 
it be generalized to work with both CD and HDD? In the latter case, no 
actual CD detection is necessary.

So is would be probably better to remove the (cdN) device names and 
accept funny names like e.g. (hd111) for boot CD 0xef. It also would be 
easier to track down problems when the boot device number is no longer 
hidden behind (cd0).

BTW: None of the BIOSes I tested provided access to a second (non-boot) 
CD drive.

Christian