[U-Boot] [PATCH] efi_loader: disk: install file system protocol to a whole disk

[AKASHI Takahiro]

On Thu, Aug 22, 2019 at 12:52:41PM +0200, Heinrich Schuchardt wrote:
> On 8/22/19 11:11 AM, Mark Kettenis wrote:
> >>From: AKASHI Takahiro <takahiro.akashi at linaro.org>
> >>Date: Thu, 22 Aug 2019 17:06:25 +0900
> >>
> >>Currently, a whole disk without any partitions is not associated
> >>with EFI_SIMPLE_FILE_SYSTEM_PROTOCOL. So even if it houses FAT
> >>file system, there is a chance that we may not be able to access
> >>it, particularly, when accesses are to be attempted after searching
> >>that protocol against a device handle.
> >>
> >>With this patch, EFI_SIMPLE_FILE_SYSTEM_PROTOCOL is installed
> >>to such a disk if part_get_info() shows there is not partition
> >>table installed on it.
> >
> >Do other UEFI implementations support this?
> 
> What use cases exist that come without partition table?

I didn't find any *explicit* description in UEFI specification
that mandates that any block device should have a partition table.
It may be mandatory for boot(able) disks, but for others?

> You can create an MBR with partition table that is a valid start of a
> file system.

Obviously we can do that, but if this is not a mandatory requirement,
we'd better support no-partitioned cases.

> So you should first check if a partition table exists. Only if none
> exists you can test for a possible file system.

I don't get your point. Are you saying that we should support a file system
for a disk only if it has a file system?
This is not true even for existing partitions as FILE_SYSTEM PROTOCOL
is always installed to every partition whether or not it really
houses a file system under the current implementation.

Thanks,
-Takahiro Akashi


> Best regards
> 
> Heinrich
> 
> >
> >>Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
> >>---
> >>  lib/efi_loader/efi_disk.c | 4 +++-
> >>  1 file changed, 3 insertions(+), 1 deletion(-)
> >>
> >>diff --git a/lib/efi_loader/efi_disk.c b/lib/efi_loader/efi_disk.c
> >>index 7a6b06821a47..548fe667e6f8 100644
> >>--- a/lib/efi_loader/efi_disk.c
> >>+++ b/lib/efi_loader/efi_disk.c
> >>@@ -239,6 +239,7 @@ static efi_status_t efi_disk_add_dev(
> >>  				struct efi_disk_obj **disk)
> >>  {
> >>  	struct efi_disk_obj *diskobj;
> >>+	disk_partition_t info;
> >>  	efi_status_t ret;
> >>
> >>  	/* Don't add empty devices */
> >>@@ -270,7 +271,8 @@ static efi_status_t efi_disk_add_dev(
> >>  			       diskobj->dp);
> >>  	if (ret != EFI_SUCCESS)
> >>  		return ret;
> >>-	if (part >= 1) {
> >>+	/* partitions or whole disk without partitions */
> >>+	if (part >= 1 || part_get_info(desc, part, &info)) {
> >>  		diskobj->volume = efi_simple_file_system(desc, part,
> >>  							 diskobj->dp);
> >>  		ret = efi_add_protocol(&diskobj->header,
> >>--
> >>2.21.0
> >>
> >>_______________________________________________
> >>U-Boot mailing list
> >>U-Boot at lists.denx.de
> >>https://lists.denx.de/listinfo/u-boot
> >
>