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

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

On Thu, Jan 10, 2019 at 05:57:11AM -0700, Simon Glass wrote:
> Hi,
> 
> On Wed, 9 Jan 2019 at 02:06, Alexander Graf <agraf@suse.de> wrote:
> >
> >
> >
> > On 13.12.18 08:58, AKASHI Takahiro wrote:
> > > Heinrich,
> > >
> > > On Tue, Dec 11, 2018 at 08:55:41PM +0100, Heinrich Schuchardt wrote:
> > >> On 11/15/18 5:58 AM, AKASHI Takahiro wrote:
> > >>> Currently, efi_init_obj_list() scan disk devices only once, and never
> > >>> change a list of efi disk devices. This will possibly result in failing
> > >>> to find a removable storage which may be added later on. See [1].
> > >>>
> > >>> In this patch, called is efi_disk_update() which is responsible for
> > >>> re-scanning UCLASS_BLK devices and removing/adding efi disks if necessary.
> > >>>
> > >>> For example,
> > >>>
> > >>> => efishell devices
> > >>> Scanning disk pci_mmc.blk...
> > >>> Found 3 disks
> > >>> Device Name
> > >>> ============================================
> > >>> /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)
> > >>> /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)/SD(0)/SD(0)
> > >>> /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)/SD(0)/SD(0)/HD(2,MBR,0x086246ba,0x40800,0x3f800)
> > >>> => usb start
> > >>> starting USB...
> > >>> USB0:   USB EHCI 1.00
> > >>> scanning bus 0 for devices... 3 USB Device(s) found
> > >>>        scanning usb for storage devices... 1 Storage Device(s) found
> > >>> => efishell devices
> > >>> Scanning disk usb_mass_storage.lun0...
> > >>> Device Name
> > >>> ============================================
> > >>> /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)
> > >>> /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)/SD(0)/SD(0)
> > >>> /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)/SD(0)/SD(0)/HD(2,MBR,0x086246ba,0x40800,0x3f800)
> > >>> /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)/USBClass(0,0,9,0,1)/USBClass(46f4,1,0,0,0)/HD(1,0x01,0,0x40,0x14fe4c)
> > >>>
> > >>> Without this patch, the last device, USB mass storage, won't show up.
> > >>>
> > >>> [1] https://lists.denx.de/pipermail/u-boot/2018-October/345307.html
> > >>>
> > >>> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> > >>
> > >> Why should we try to fix something in the EFI subsystems that goes wrong
> > >> in the handling of device enumeration.
> > >
> > > No.
> > > This is a natural result from how efi disks are currently implemented on u-boot.
> > > Do you want to totally re-write/re-implement efi disks?
> >
> > Could we just make this event based for now? Call a hook from the
> > storage dm subsystem when a new u-boot block device gets created to
> > issue a sync of that in the efi subsystem?
> >
> 
> Please no. We don't want EFI hooks around the place. EFI should use
> DM, not the other way around.

Right, but every efi disk is associated with a backing "u-boot"
block devices (even more, this is not 1-to-1 mapping but many-to-1 due to
partitions).
Without any sort of event/hook mechanism, we can know of all block
devices only by enumerating them at some point as in my current
approach. Do you want to accept this?

(Even in a hacky way. See efi_disk_register():
        for (if_type = 0; if_type < IF_TYPE_COUNT; if_type++)
		...
                printf("Scanning disks on %s...\n", if_typename);
                for (i = 0; i < 4; i++) {    <= !!!
                        desc = blk_get_devnum_by_type(if_type, i);
	...
)

> > That hook would obviously only do something (or get registered?) when
i 
> > the efi object stack is initialized.
> >
> > The long term goal IMHO should still be though to just merge DM and EFI
> > objects. But we're still waiting on the deprecation of non-DM devices
> > for that.
> 
> I think think 'merge' is the right word. Perhaps 'create EFI devices
> in DM' is a better term.

How different is your idea from UCLASS_BLK device(efi_block_device.c)?

The current implementation of UCLASS_BLK, in my opinion, is somehow
in a half way; an instance of UCLASS_BLK is created only when a
efi driver is bound to a controller.
In the meantime, efi disks (efi objects which support UEFI_BLOCK_IO_PROTOCOL)
is implicitly created in efi_disk_add_dev() without any *binding*.

> Anyway, let's do that now. As I may have mentioned we should never
> have enabled EFI on pre-DM boards :-) It has just lead to duplication.
> 
> In any case, the migration deadline for DM_MMC (for example) is the
> upcoming merge window, so the time is now.
> 
> As things stand this patch looks reasonable to me. It is a natural
> consequence of duplicating the DM tables.

I think so, yes.

-Takahiro Akashi

> Regards,
> Simon