Re: [PATCH v4 09/34] efi: Add EFI uclass for media

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

On Sun, Nov 07, 2021 at 09:43:22AM -0700, Simon Glass wrote:
> Hi Heinrich,
> 
> On Sun, 7 Nov 2021 at 01:21, Heinrich Schuchardt <xypron.glpk@gmx.de> wrote:
> >
> >
> >
> > On 11/4/21 04:09, Simon Glass wrote:
> > > At present UCLASS_EFI is used to represent an EFI filesystem among other
> > > things. The description of this uclass is "EFI managed devices" which is
> > > pretty vague. The only driver that uses this uclass is in fact not a real
> > > U-Boot driver, since its operations do not include a struct udevice.
> > >
> > > Rather than mess with this, create a new UCLASS_EFI_MEDIA uclass to handle
> > > EFI media such as disks. Make this the uclass to use for EFI media so that
> > > it can be used with 'part list', for example.
> > >
> > > The existing implementation using UCLASS_EFI remains as is, for
> > > discussion.
> > >
> > > Signed-off-by: Simon Glass <sjg@chromium.org>
> > > ---
> > >
> > > (no changes since v2)
> > >
> > > Changes in v2:
> > > - Add MAINTAINERS entry
> > > - Show the correct interface type with 'part list'
> > > - Update the commit message to explain things better
> > >
> > >   MAINTAINERS                      |  3 +++
> > >   arch/sandbox/dts/test.dts        |  4 ++++
> > >   disk/part.c                      |  5 ++++-
> > >   drivers/block/Kconfig            | 23 +++++++++++++++++++++++
> > >   drivers/block/Makefile           |  3 +++
> > >   drivers/block/blk-uclass.c       |  2 +-
> > >   drivers/block/efi-media-uclass.c | 15 +++++++++++++++
> > >   drivers/block/sb_efi_media.c     | 20 ++++++++++++++++++++
> > >   include/dm/uclass-id.h           |  1 +
> > >   test/dm/Makefile                 |  1 +
> > >   test/dm/efi_media.c              | 24 ++++++++++++++++++++++++
> > >   11 files changed, 99 insertions(+), 2 deletions(-)
> > >   create mode 100644 drivers/block/efi-media-uclass.c
> > >   create mode 100644 drivers/block/sb_efi_media.c
> > >   create mode 100644 test/dm/efi_media.c
> > >
> > > diff --git a/MAINTAINERS b/MAINTAINERS
> > > index 00ff572d4d2..3e8f10c72fa 100644
> > > --- a/MAINTAINERS
> > > +++ b/MAINTAINERS
> > > @@ -712,8 +712,11 @@ W:       https://u-boot.readthedocs.io/en/latest/develop/uefi/u-boot_on_efi.html
> > >   F:  board/efi/efi-x86_app
> > >   F:  configs/efi-x86_app*
> > >   F:  doc/develop/uefi/u-boot_on_efi.rst
> > > +F:   drivers/block/efi-media-uclass.c
> > > +F:   drivers/block/sb_efi_media.c
> > >   F:  lib/efi/efi_app.c
> > >   F:  scripts/build-efi.sh
> > > +F:   test/dm/efi_media.c
> > >
> > >   EFI PAYLOAD
> > >   M:  Heinrich Schuchardt <xypron.glpk@gmx.de>
> > > diff --git a/arch/sandbox/dts/test.dts b/arch/sandbox/dts/test.dts
> > > index 8cd688e8d26..2cea4a43c87 100644
> > > --- a/arch/sandbox/dts/test.dts
> > > +++ b/arch/sandbox/dts/test.dts
> > > @@ -498,6 +498,10 @@
> > >               compatible = "sandbox,clk-ccf";
> > >       };
> > >
> > > +     efi-media {
> > > +             compatible = "sandbox,efi-media";
> > > +     };
> > > +
> > >       eth@10002000 {
> > >               compatible = "sandbox,eth";
> > >               reg = <0x10002000 0x1000>;
> > > diff --git a/disk/part.c b/disk/part.c
> > > index a6a8f7052bd..2560f6a50bc 100644
> > > --- a/disk/part.c
> > > +++ b/disk/part.c
> > > @@ -296,8 +296,11 @@ static void print_part_header(const char *type, struct blk_desc *dev_desc)
> > >       case IF_TYPE_VIRTIO:
> > >               puts("VirtIO");
> > >               break;
> > > +     case IF_TYPE_EFI:
> > > +             puts("EFI");
> > > +             break;
> > >       default:
> > > -             puts ("UNKNOWN");
> > > +             puts("UNKNOWN");
> > >               break;
> > >       }
> > >       printf (" device %d  --   Partition Type: %s\n\n",
> > > diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
> > > index 56a4eec05ac..755fdccb574 100644
> > > --- a/drivers/block/Kconfig
> > > +++ b/drivers/block/Kconfig
> > > @@ -61,6 +61,29 @@ config TPL_BLOCK_CACHE
> > >       help
> > >         This option enables the disk-block cache in TPL
> > >
> > > +config EFI_MEDIA
> > > +     bool "Support EFI media drivers"
> > > +     default y if EFI || SANDBOX
> > > +     help
> > > +       Enable this to support media devices on top of UEFI. This enables
> > > +       just the uclass so you also need a specific driver to make this do
> > > +       anything.
> > > +
> > > +       For sandbox there is a test driver.
> > > +
> > > +if EFI_MEDIA
> > > +
> > > +config EFI_MEDIA_SANDBOX
> > > +     bool "Sandbox EFI media driver"
> > > +     depends on SANDBOX
> > > +     default y
> > > +     help
> > > +       Enables a simple sandbox media driver, used for testing just the
> > > +       EFI_MEDIA uclass. It does not do anything useful, since sandbox does
> > > +       not actually support running on top of UEFI.
> > > +
> > > +endif  # EFI_MEDIA
> > > +
> > >   config IDE
> > >       bool "Support IDE controllers"
> > >       select HAVE_BLOCK_DEVICE
> > > diff --git a/drivers/block/Makefile b/drivers/block/Makefile
> > > index 94ab5c6f906..3778633da1d 100644
> > > --- a/drivers/block/Makefile
> > > +++ b/drivers/block/Makefile
> > > @@ -14,3 +14,6 @@ obj-$(CONFIG_IDE) += ide.o
> > >   endif
> > >   obj-$(CONFIG_SANDBOX) += sandbox.o
> > >   obj-$(CONFIG_$(SPL_TPL_)BLOCK_CACHE) += blkcache.o
> > > +
> > > +obj-$(CONFIG_EFI_MEDIA) += efi-media-uclass.o
> > > +obj-$(CONFIG_EFI_MEDIA_SANDBOX) += sb_efi_media.o
> > > diff --git a/drivers/block/blk-uclass.c b/drivers/block/blk-uclass.c
> > > index 83682dcc181..2db7ce5de20 100644
> > > --- a/drivers/block/blk-uclass.c
> > > +++ b/drivers/block/blk-uclass.c
> > > @@ -44,7 +44,7 @@ static enum uclass_id if_type_uclass_id[IF_TYPE_COUNT] = {
> > >       [IF_TYPE_SATA]          = UCLASS_AHCI,
> > >       [IF_TYPE_HOST]          = UCLASS_ROOT,
> > >       [IF_TYPE_NVME]          = UCLASS_NVME,
> > > -     [IF_TYPE_EFI]           = UCLASS_EFI,
> > > +     [IF_TYPE_EFI]           = UCLASS_EFI_MEDIA,
> >
> > Don't break existing code. Create a new if_type here.
> 
> My understanding is that this is not actually used at present. The
> tests appear to pass without trouble.
> 
> What problem are you seeing?

I can agree with Simon's claim that the notion of UCLASS_EFI sounds vague.
In my understanding, it is expected to represent any UEFI driver/application
who will convert "UEFI protocol" to "U-Boot device", the only example
right now is "efi_block" device.

One of issues that I can see is that any instance of UCLASS_EFI doesn't
appear in DM tree. I have made an experimental patch which makes UCLASS_EFI
a pseudo U-Boot device. DM tree would look like:
  root
  |-- 'EFI block driver' (CLASS_EFI for block_io_protocol)
      |-- 'efi_blk' (CLASS_BLK with TYPE_EFI)

This way, the meaning of UCLASS_EFI should be much clearer?

# In fact, the actual implementer of BLOCK_IO_PROTOCOL is
# a loaded UEFI application, though.

-Takahiro Akashi

> Regards,
> Simon