> On 12/16/2013 12:28 AM, Ruben Kerkhof wrote: > > > > On 15 dec. 2013, at 20:21, Ady <ady-sf at hotmail.com> wrote: > > > > Hi Ady, > > > >> Please forgive my ignorance. Could someone point to some "standard" > >> or some documentation where the supposedly correct / adequate value > >> (EE or ED or whichever) is specifically listed and/or explained? > >> > >> For example, where is this "ED" partition type ID listed where it > >> specifically makes reference (or in relation) to *EFI*? > >> > >> The reason I ask is because I know about "EE" and "EF" partition > >> typed IDs in relation to EFI, but not about "ED" (in relation to > >> EFI). Perhaps I am just misunderstanding this email thread (?). > > > > That's what I thought, and I haven't found any reference to ED, except for > > doc/gpt.txt which talks about "the T13-approved protocol for GPT partitions with BIOS > > firmware." > > > > Yes, it is in the T13 EDD documentation. > > -hpaHere is what I found. 24 July 2009 (older) e09127r0 "EDD-4 Hybrid MBR support" [/quote] Set to the OS Type field of the Partition Record of the bootable partition. Set to 0xED if the bootable partition is from GPT. [/quote] 4 January 2010 (newer) e09127r3 "EDD-4 Hybrid MBR boot code annex" [quote] Set to the OS Type of the bootable partition (i.e., that would have been assigned had the partition been installed in an MBR disk layout). [/quote] So, in the older revision, "ED" is explicitly mentioned. In a newer revision there is no explicit mention of an ID code. I still see popular sites with lists of partition IDs with "EE" and "EF" in relation to EFI, and AFAIK there is no (other) "standard" for GPT in BIOS. I wonder whether other documents / standards explicitly mention *any* partition ID, and whether these IDs could potentially result in future inconsistencies / problems / bugs / hours of tracking down strange (mis)behaviors. Regards, Ady.
On 12/16/2013 01:41 PM, Ady wrote:> > 4 January 2010 (newer) > e09127r3 > "EDD-4 Hybrid MBR boot code annex" > [quote] > Set to the OS Type of the bootable partition (i.e., > that would have been assigned had the partition > been installed in an MBR disk layout). > [/quote] > > So, in the older revision, "ED" is explicitly mentioned. In a newer > revision there is no explicit mention of an ID code. > > I still see popular sites with lists of partition IDs with "EE" and > "EF" in relation to EFI, and AFAIK there is no (other) "standard" for > GPT in BIOS. > > I wonder whether other documents / standards explicitly mention *any* > partition ID, and whether these IDs could potentially result in > future inconsistencies / problems / bugs / hours of tracking down > strange (mis)behaviors. >You're right - T13 changed the "OS Type" from 0xED to "that would have been assigned had the partition been installed in an MBR disk layout". That is kind of hard to accomplish without blowing the MBR code size budget, since it effectively requires a mapping from GUIDs to OS types. In practice I doubt it matters, though. -hpa
> On 12/16/2013 01:41 PM, Ady wrote: > > > > 4 January 2010 (newer) > > e09127r3 > > "EDD-4 Hybrid MBR boot code annex" > > [quote] > > Set to the OS Type of the bootable partition (i.e., > > that would have been assigned had the partition > > been installed in an MBR disk layout). > > [/quote] > > > > So, in the older revision, "ED" is explicitly mentioned. In a newer > > revision there is no explicit mention of an ID code. > > > > I still see popular sites with lists of partition IDs with "EE" and > > "EF" in relation to EFI, and AFAIK there is no (other) "standard" for > > GPT in BIOS. > > > > I wonder whether other documents / standards explicitly mention *any* > > partition ID, and whether these IDs could potentially result in > > future inconsistencies / problems / bugs / hours of tracking down > > strange (mis)behaviors. > > > > You're right - T13 changed the "OS Type" from 0xED to "that would have > been assigned had the partition been installed in an MBR disk layout". > That is kind of hard to accomplish without blowing the MBR code size > budget, since it effectively requires a mapping from GUIDs to OS types. > In practice I doubt it matters, though. > > -hpaI assume that the intention to use a (theoretical and desired) match between the partition ID and the filesystem is to "imitate" the common traditional MBR usage, for a (theoretical) closer backward compatibility. Now, if the newer T13 documentation doesn't specifically refer to "ED" as partition ID for the "hybrid" MBR boot code handover in GPT, then some questions remain: _ Is the original desire *not* to use "EE" still relevant? _ If no particular "matched" ID is used in gptmbr.bin, should "ED" still be used? I wonder whether it would be better to change it (back) to "EE" (?). FWIW, UEFI 2.4 says: [quote] 0xEE (i.e., GPT Protective) is used by a protective MBR (see 5.2.2) to define a fake partition covering the entire disk. [/quote] Regards, Ady.