[U-Boot] [PATCH v2 2/3] efi_loader: disk: install FILE_SYSTEM_PROTOCOL only if available

[AKASHI Takahiro <takahiro.akashi@linaro.org>]

On Thu, Sep 12, 2019 at 11:43:07AM +0200, Heinrich Schuchardt wrote:
> On 9/12/19 11:17 AM, AKASHI Takahiro wrote:
> > On Thu, Sep 12, 2019 at 10:57:20AM +0200, Heinrich Schuchardt wrote:
> >> On 9/12/19 6:51 AM, AKASHI Takahiro wrote:
> >>> In the current implementation, EFI_SIMPLEFILE_SYSTEM_PROTOCOL is always
> >>> installed to all the partitions even if some of them may house no file
> >>> system.
> >>>
> >>> With this patch, that protocol will be installed only if FAT file system
> >>> exists.
> >>>
> >>> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> >>> ---
> >>>  lib/efi_loader/efi_disk.c | 16 +++++++++++++++-
> >>>  1 file changed, 15 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/lib/efi_loader/efi_disk.c b/lib/efi_loader/efi_disk.c
> >>> index 7a6b06821a47..d72f455901f2 100644
> >>> --- a/lib/efi_loader/efi_disk.c
> >>> +++ b/lib/efi_loader/efi_disk.c
> >>> @@ -9,6 +9,7 @@
> >>>  #include <blk.h>
> >>>  #include <dm.h>
> >>>  #include <efi_loader.h>
> >>> +#include <fs.h>
> >>>  #include <part.h>
> >>>  #include <malloc.h>
> >>>
> >>> @@ -217,6 +218,19 @@ efi_fs_from_path(struct efi_device_path *full_path)
> >>>  	return handler->protocol_interface;
> >>>  }
> >>>
> >>> +static int efi_fs_exists(struct blk_desc *desc, int part)
> >>> +{
> >>> +	if (fs_set_blk_dev_with_part(desc, part))
> >>> +		return 0;
> >>> +
> >>> +	if (strcmp(fs_get_type_name(), "fat"))
> >>
> >> Before your patch we could use any supported file system (e.g. EXT2). I
> >> see no need for a restriction to FAT. You could compare the string to
> >> "unsupported":
> >
> > No. As far as you want to stick to compliance to UEFI specification,
> > "fat" is the only file system supported by UEFI.
> 
> In the case of device path node VenHw() there is a direct rule in the
> spec indicating how it should be rendered. I have not seen anything in
> the UEFI spec saying that you should not support file systems besides
> FAT. So there is no compliance issue. I would be reluctant to remove an
> existing capability of U-Boot.

See section 13.3. It says,
        The file system supported by the Extensible Firmware Interface is
        based on the FAT file system.

-Takahiro Akashi

> >
> >> if (!strcmp(fs_get_type_name(), "unsupported"))
> >> 	return 0;
> >>
> >> But wouldn't it be preferable to have a function to access fs_type (in
> >> fs/fs.c) directly instead of a string representation?
> >
> > Agree, but there is no direct function in fs/fs.c.
> > I'm reluctant to invent a new function just for this purpose.
> 
> In that case we should compare to a string that is defined as constant
> in fs.h.
> 
> Best regards
> 
> Heinrich
> 
> >
> > -Takahiro Akashi
> >
> >
> >> Otherwise we should convert the string "unsupported" of fstypes[] into a
> >> constant in fs.h so that we can be sure we are using the same value.
> >>
> >> Best regards
> >>
> >> Heinrich
> >>
> >>> +		return 0;
> >>> +
> >>> +	fs_close();
> >>> +
> >>> +	return 1;
> >>> +}
> >>> +
> >>>  /*
> >>>   * Create a handle for a partition or disk
> >>>   *
> >>> @@ -270,7 +284,7 @@ static efi_status_t efi_disk_add_dev(
> >>>  			       diskobj->dp);
> >>>  	if (ret != EFI_SUCCESS)
> >>>  		return ret;
> >>> -	if (part >= 1) {
> >>> +	if (part >= 1 && efi_fs_exists(desc, part)) {
> >>>  		diskobj->volume = efi_simple_file_system(desc, part,
> >>>  							 diskobj->dp);
> >>>  		ret = efi_add_protocol(&diskobj->header,
> >>>
> >>
> >
>