[U-Boot] [PATCH v2 2/3] efi_loader: enumerate disk devices every time

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

Simon,

On Mon, Jan 28, 2019 at 05:46:21PM -0700, Simon Glass wrote:
> Hi,
> 
> On Mon, 28 Jan 2019 at 01:55, AKASHI Takahiro
> <takahiro.akashi@linaro.org> wrote:
> >
> > On Fri, Jan 25, 2019 at 10:31:20AM +0100, Alexander Graf wrote:
> > >
> > >
> > > On 25.01.19 10:18, AKASHI Takahiro wrote:
> > > > On Fri, Jan 25, 2019 at 09:52:31AM +0100, Alexander Graf wrote:
> > > >>
> > > >>
> > > >> On 25.01.19 09:27, AKASHI Takahiro wrote:
> > > >>> Alex,
> > > >>>
> > > >>> On Wed, Jan 23, 2019 at 10:51:29AM +0100, Alexander Graf wrote:
> > > >>>> On 01/22/2019 08:39 PM, Simon Glass wrote:
> > > >>>>> Hi Alex,
> > > >>>>>
> > > >>>>> On Tue, 22 Jan 2019 at 22:08, Alexander Graf <agraf@suse.de> wrote:
> > > >>>>>>
> > > >>>>>>
> > > >>>>>> On 22.01.19 09:29, AKASHI Takahiro wrote:
> > > >>>>>>> Alex, Simon,
> > > >>>>>>>
> > > >>>>>>> Apologies for my slow response on this matter,
> > > >>>>>>>
> > > >>>>>>> On Fri, Jan 11, 2019 at 08:57:05AM +0100, Alexander Graf wrote:
> > > >>>>>>>>
> > > >>>>>>>> On 11.01.19 05:29, AKASHI Takahiro wrote:
> > > >>>>>>>>> Alex, Heinrich and Simon,
> > > >>>>>>>>>
> > > >>>>>>>>> Thank you for your comments, they are all valuable but also make me
> > > >>>>>>>>> confused as different people have different requirements :)
> > > >>>>>>>>> I'm not sure that all of us share the same *ultimate* goal here.
> > > >>>>>>>> The shared ultimate goal is to "merge" (as Simon put it) dm and efi objects.
> > > >>>>>>> I don't still understand what "merge" means very well.
> > > >>>>>> It basically means that "struct efi_object" moves into "struct udevice".
> > > >>>>>> Every udevice instance of type UCLASS_BLK would expose the block and
> > > >>>>>> device_path protocols.
> > > >>>>>>
> > > >>>>>> This will be a slightly bigger rework, but eventually allows us to
> > > >>>>>> basically get rid of efi_init_obj_list() I think.
> > > >>>>> I envisaged something like:
> > > >>>>>
> > > >>>>> - EFI objects have their own UCLASS_EFI uclass
> > > >>>>
> > > >>>> ... and then we need to create our own sub object model around the
> > > >>>> UCLASS_EFI devices again. I' not convinced that's a great idea yet :). I
> > > >>>> really see little reason not to just expose every dm device as EFI handle.
> > > >>>> Things would plug in quite naturally I think.
> > > >>>
> > > >>> You said that the ultimate goal is to remove all efi_object data.
> > > >>> Do you think that all the existing efi_object can be mapped to
> > > >>> one of existing u-boot uclass devices?
> > > >>>
> > > >>> If so, what would be an real entity of a UEFI handle?
> > > >>> struct udevice *?
> > > >>>
> > > >>> But Simon seems not to agree to adding any UEFI-specific members
> > > >>> in struct udevice.
> > > >>
> > > >> I think we'll have to experiment with both approaches. I personally
> > > >> would like to have struct udevice * be the UEFI handle, yes.
> > > >>
> > > >>>
> > > >>>> But either way, someone would need to sit down and prototype things to be
> > > >>>> sure.
> > > >>>>
> > > >>>
> > > >>> The most simplest prototype would include
> > > >>> * event mechanism (just registration and execution of hook/handler)
> > > >>>     event: udevice creation (and deletion)
> > > >>> * efi_disk hook for udevice(UCLASS_BLK) creation
> > > >>> * modified block device's enumeration code, say, scsi_scan(),
> > > >>>   to add an event hook at udevice creation
> > > >>> * removing efi_disk_register() from efi_init_obj_list()
> > > >>> * Optionally(?) UCLASS_PARTITION
> > > >>>   (Partition udevices would be created in part_init().)
> > > >>
> > > >> Almost.
> > > >>
> > > >> The simplest prototype would be to add a struct efi_object into struct
> > > >> udevice. Then whenever we're looping over efi_obj_list in the code, we
> > > >> additionally loop over all udevices to find the handle.
> > > >
> > > > Ah, yes. You're going further :)
> > > >
> > > >> Then, we could slowly give the uclasses explicit knowledge of uefi
> > > >> protocols. So most of the logic of efi_disk_register() would move into
> > > >> (or get called by) drivers/block/blk-uclass.c:blk_create_device().
> > > >
> > > > Via event? Otherwise, we cannot decouple u-boot and UEFI world.
> > >
> > > For a prototype, just make it explicit and see how far that gets us.
> > >
> > > >> Instead of creating diskobj and adding calling efi_add_handle(), we
> > > >> could then just use existing data structure from the udevice (and its
> > > >> platdata).
> > > >
> > > > I don't have good confidence that we can remove struct efi_disk_obj,
> > > > at least, for the time being as some of its members are quite UEFI-specific.
> > >
> > > Maybe we can move them into struct blk_desc? It's a matter of
> > > experimenting I guess.
> > >
> > > >
> > > >>
> > > >> Does this make sense? Less events, more implicity :).
> > > >
> > > > I'll go for it.
> > >
> > > Thanks a lot :). Feel free to pick an easier target for starters too if
> > > you prefer.
> >
> > Prototyping is done :)
> > Since it was so easy and simple, now I'm thinking of implementing
> > UCLASS_PARTITION. But it is not so straightforward as I expected,
> > and it won't bring us lots of advantages.
> > (I think that blk_desc should also support a partition in its own.)
> 
> blk_desc is in UCLASS_BLK. So we already support partitions within
> blk_desc. Can you expand a bit on what you mean?

This is partly because "efi_disk_obj" structure is embedded in
blk_desc for now. So for UCLASS_PARTITION, we need a dummy blk_desc.

> >
> >
> > Once it gets working, may I send out a patch?
> 
> Yes indeed.

Shortly. We will continue to discuss after my patch is released.

Thanks,
-Takahiro Akashi


> Regards,
> Simon
> 
> >
> > -Takahiro Akashi
> >
> >
> > >
> > > Alex