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

Thu Jan 10 08:02:17 UTC 2019

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()?).

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() :)

-Takahiro Akashi

> 
> Alex