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

Thu Jan 10 09:16:09 UTC 2019

On Thu, Jan 10, 2019 at 09:15:36AM +0100, Alexander Graf wrote:
> 
> 
> > Am 10.01.2019 um 09:02 schrieb AKASHI Takahiro <takahiro.akashi at linaro.org>:
> > 
> >> On Thu, Jan 10, 2019 at 08:30:13AM +0100, Alexander Graf wrote:
> >> 
> >> 
> >>> On 10.01.19 08:26, AKASHI Takahiro wrote:
> >>> Alex,
> >>> 
> >>>> On Thu, Jan 10, 2019 at 07:21:12AM +0100, Alexander Graf wrote:
> >>>> 
> >>>> 
> >>>>> On 10.01.19 03:13, AKASHI Takahiro wrote:
> >>>>> Alex,
> >>>>> 
> >>>>>> On Wed, Jan 09, 2019 at 10:06:16AM +0100, Alexander Graf 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 at 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?
> >>>>> 
> >>>>> If I correctly understand you, your suggestion here corresponds
> >>>>> with my proposal#3 in [1] while my current approach is #2.
> >>>>> 
> >>>>> [1] https://lists.denx.de/pipermail/u-boot/2018-October/345307.html
> >>>> 
> >>>> Yes, I think so.
> >>>> 
> >>>>> So we will call, say, efi_disk_create(struct udevice *) in
> >>>>> blk_create_device() and efi_dsik_delete() in blk_unbind_all().
> >>>> 
> >>>> I would prefer if we didn't call them directly, but through an event
> >>>> mechanism. So the efi_disk subsystem registers an event with the dm
> >>>> block subsystem and that will just call all events when block devices
> >>>> get created which will automatically also include the efi disk creation
> >>>> callback. Same for reverse.
> >>> 
> >>> Do you mean efi event by "event?"
> >>> (I don't think there is any generic event interface on DM side.)
> >>> 
> >>> Whatever an "event" is or whether we call efi_disk_create() directly
> >>> or indirectly via an event, there is one (big?) issue in this approach
> >>> (while I've almost finished prototyping):
> >>> 
> >>> We cannot call efi_disk_create() within blk_create_device() because
> >>> some data fields of struct blk_desc, which are to be used by efi disk,
> >>> are initialized *after* blk_create_device() in driver side.
> >>> 
> >>> So we need to add a hook at/after every occurrence of blk_create_device()
> >>> on driver side. For example,
> >>> 
> >>> === drivers/scsi/scsi.c ===
> >>> int do_scsi_scan_one(struct udevice *dev, int id, int lun, bool verbose)
> >>> {
> >>>    ...
> >>>    ret = blk_create_devicef(dev, "scsi_blk", str, IF_TYPE_SCSI, -1,
> >>>                   bd.blksz, bd.lba, &bdev);
> >>>    ...
> >>>    bdesc = dev_get_uclass_platdata(bdev);
> >>>    bdesc->target = id;
> >>>    bdesc->lun = lun;
> >>>    ...
> >>> 
> >>>    /*
> >>>     * We need have efi_disk_create() called here because bdesc->target
> >>>     * and lun will be used by dp helpers in efi_disk_add_dev().
> >>>     */
> >>>    efi_disk_create(bdev);
> >>> }
> >>> 
> >>> int scsi_scan_dev(struct udevice *dev, bool verbose)
> >>> {
> >>>        for (i = 0; i < uc_plat->max_id; i++)
> >>>                for (lun = 0; lun < uc_plat->max_lun; lun++)
> >>>                        do_scsi_scan_one(dev, i, lun, verbose);
> >>>    ...
> >>> }
> >>> 
> >>> int scsi_scan(bool verbose)
> >>> {
> >>>    ret = uclass_get(UCLASS_SCSI, &uc);
> >>>    ...
> >>>        uclass_foreach_dev(dev, uc)
> >>>                ret = scsi_scan_dev(dev, verbose);
> >>>    ...
> >>> }
> >>> === ===
> >>> 
> >>> Since scsn_scan() can be directly called by "scsi rescan" command,
> >>> There seems to be no generic hook, or event, available in order to
> >>> call efi_disk_create().
> >>> 
> >>> Do I miss anything?
> >> 
> >> Could the event handler that gets called from somewhere around
> >> blk_create_device() just put it into an efi internal "todo list" which
> >> we then process using an efi event?
> >> 
> >> EFI events will only get triggered on the next entry to efi land, so by
> >> then we should be safe.
> > 
> > I think I now understand your suggestion; we are going to invent
> > a specialized event-queuing mechanism so that we can take any actions
> > later at appropriate time (probably in efi_init_obj_list()?).
> 
> Uh, not sure I follow. There would be 2 events. One from the u-boot block layer to the efi_loader disk layer.

This is a to-be-invented "specialized event-queuing mechanism"
in my language :) as we cannot use efi_create/signal_event() before
initializing EFI environment.

This event will be expected to be 'signal'ed at every creation/deletion
of UCLASS_BLK device. Right?

> That event handler creates a new efi event (like a timer w/ timeout=0).

But when is this event handler fired?
I think the only possible timing is at efi_init_obj_list().

> This new event's handler can then create the actual efi block device.

I assume that this event handler is fired immediately after
efi_signal_event() with timeout=0.

If so, why do we need to create an efi event? To isolate the disk code
from the other init code?

(If so, for the same reason, we should re-write efi_init_obj_list()
with events for other efi resources as well.)

> > 
> > But if so, it's not much different from my current approach where
> > a list of efi disks are updated in efi_init_obj_list() :)
> 
> The main difference is that disk logic stays in the disc code scope :).

My efi_disk_update() (and efi_disk_register()) is the only function
visible outside the disk code, isn't it?

Using some kind of events here is smart, but looks to me a bit overdoing
because we anyhow have to go through all the UCLASS_BLK devices to mark
whether they are still valid or not :)

-Takahiro Akashi

> Alex
> 
> > 
> > -Takahiro Akashi
> > 
> > 
> >> 
> >> Alex
> 