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

Alexander Graf
2019-01-10T08:15:36Z

> Am 10.01.2019 um 09:02 schrieb AKASHI Takahiro <takahiro.akashi@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@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. That event handler creates a new efi event (like a timer w/ timeout=0). This new event's handler can then create the actual efi block device.

>
> 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 :).

Alex

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