On 05/07/2018 08:46 PM, Rob Herring wrote:
On Mon, May 7, 2018 at 12:17 PM, William Mills wmills@ti.com wrote:
On 05/07/2018 11:49 AM, Rob Herring wrote:
On Fri, May 4, 2018 at 1:41 PM, William Mills wmills@ti.com wrote:
On 05/04/2018 01:03 PM, Andreas Färber wrote:
Am 04.05.2018 um 18:50 schrieb Alexander Graf:
On 05/04/2018 06:20 PM, William Mills wrote: > On 05/04/2018 11:45 AM, Alexander Graf wrote: > I am missing something. If there is only MBR and no GPT then there is > no GUID type for EFI Partition. So how does the firmware find the "EFI > Partition" and the default /efi/boot/boot*.efi file? Does it just use > the partition with boot flag? There is a special partition ID for the ESP (0xEF), but U-Boot currently just searches on every partition that's marked bootable.
... and falls back to the first partition if none on the device is marked bootable.
Thanks guys, that makes sense.
So the running summary in my head looks like this:
Case #1: Platforms that have separate storage for firmware and OS
OS storage is simple std GPT with no funny MBR stuff. One image may work on many boards.
Case #2: Platforms where firmware and OS share single storage
Storage uses either GPT or MBR (but only one) based on board need. Image is dedicated for one machine type (or closely related set). If raw mode is needed use MBR with 2MB reserved space OS should not touch reserved space in MBR If using GPT, firmware should place needed files in either: * Vendor registered dir in EFI partition * GUID identified partitions w/ attribute bit 0 set (can fallback to using names if GUID not found)
This is for all the other stuff vendors stick in custom partitions if we're lucky or some fixed offset if we're not, right?
Yes. Today people seem to be using a GPT partition for each of these low level objects and seem to be using the partition name to identify them. They are using very generic names like "boot".
This means that the disk image will only work with one SOC or perhaps even one board.
If people are going to use raw GPT partitions I think they should at least use a GUID GPT partition type to give certainty. Falling back to a name is OK and will help the casual user.
Bit 0 of the GPT attributes table is listed as "Platform required". Do current installers leave these partitions alone?
I'll leave that to one of the OS folks.
I double checked with our YaST people. The "Platform required" bit in GPT gets translated to the "hidden" bit in parted. That bit is then happily ignored by our installer.
So the installer may consider the partition ok to remove.
Alex