Re: [OE-core][PATCH] grub: update search parameter

[Xiangyu Chen <xiangyu.chen@windriver.com>]

Hi Paul,


On 3/5/26 19:49, Paul Barker wrote:
> I'm not sure that this can work for all use cases. The grub
> documentatation for hints says "First try the device HINT" (i.e. it's
> explicitly a device), whereas the documentation for cmdpath says that it
> is "an absolute directory name".
While the documentation defines $cmdpath as a directory and hints as 
devices, grub’s internal implementation of
grub_disk_open (grub-core/kern/disk.c [1]) is designed to handle this 
exact "device+path" format.

When a hint like (hd0,gpt1)/EFI/BOOT/ is passed, grub_disk_open calls 
find_part_sep to locate the partition/path delimiter.
It then uses grub_memcpy to extract only the device part (e.g., (hd0) 
into the raw buffer for the disk driver.

The remaining string (gpt1)/EFI/BOOT/) is passed to 
grub_partition_probe, which identifies the partition and gracefully
ignores the trailing directory path.

The current syntax ($cmdpath) results in double parentheses ((hd0...)) 
if the variable is already populated.
In grub_disk_open, this extracts a malformed device name ((hd0 which no 
driver can open, triggering a hard no such device error.


Ref:

[1] 
https://elixir.bootlin.com/grub/grub-2.14/source/grub-core/kern/disk.c#L192


Br,

Xiangyu