[PATCH 1/1] dm: fix blk_get_devnum_by_uclass_idname()
Heinrich Schuchardt
heinrich.schuchardt at canonical.com
Wed Oct 12 08:56:09 CEST 2022
On 10/12/22 02:30, AKASHI Takahiro wrote:
> On Tue, Oct 11, 2022 at 03:54:32PM -0600, Simon Glass wrote:
>> Hi Heinrich,
>>
>> On Tue, 11 Oct 2022 at 14:17, Heinrich Schuchardt
>> <heinrich.schuchardt at canonical.com> wrote:
>>>
>>> On 10/11/22 16:16, Simon Glass wrote:
>>>> Hi Heinrich,
>>>>
>>>> On Tue, 11 Oct 2022 at 04:38, Heinrich Schuchardt
>>>> <heinrich.schuchardt at canonical.com> wrote:
>>>>>
>>>>>
>>>>>
>>>>> On 10/11/22 07:46, Heinrich Schuchardt wrote:
>>>>>>
>>>>>>
>>>>>> On 10/11/22 01:49, Simon Glass wrote:
>>>>>>> Hi Heinrich,
>>>>>>>
>>>>>>> On Thu, 6 Oct 2022 at 14:05, Heinrich Schuchardt
>>>>>>> <heinrich.schuchardt at canonical.com> wrote:
>>>>>>>>
>>>>>>>> On 10/3/22 18:44, Simon Glass wrote:
>>>>>>>>> Hi Heinrich,
>>>>>>>>>
>>>>>>>>> On Mon, 3 Oct 2022 at 10:33, Heinrich Schuchardt
>>>>>>>>> <heinrich.schuchardt at canonical.com> wrote:
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> On 10/3/22 16:57, Simon Glass wrote:
>>>>>>>>>>> Hi Heinrich,
>>>>>>>>>>>
>>>>>>>>>>> On Mon, 3 Oct 2022 at 03:36, Heinrich Schuchardt
>>>>>>>>>>> <heinrich.schuchardt at canonical.com> wrote:
>>>>>>>>>>>>
>>>>>>>>>>>> On the sandbox I run:
>>>>>>>>>>>>
>>>>>>>>>>>> => setenv efi_selftest block device
>>>>>>>>>>>> => bootefi selftest
>>>>>>>>>>>>
>>>>>>>>>>>> and see the following output:
>>>>>>>>>>>>
>>>>>>>>>>>> ** Bad device specification host 0 **
>>>>>>>>>>>> Couldn't find partition host 0:0
>>>>>>>>>>>> Cannot read EFI system partition
>>>>>>>>>>>>
>>>>>>>>>>>> Running
>>>>>>>>>>>>
>>>>>>>>>>>> => lsblk
>>>>>>>>>>>>
>>>>>>>>>>>> yields
>>>>>>>>>>>>
>>>>>>>>>>>> Block Driver Devices
>>>>>>>>>>>> -----------------------------
>>>>>>>>>>>> efi_blk : efiloader 0
>>>>>>>>>>>> ide_blk : <none>
>>>>>>>>>>>> mmc_blk : mmc 2, mmc 1, mmc 0
>>>>>>>>>>>> nvme-blk : <none>
>>>>>>>>>>>> sandbox_host_blk : <none>
>>>>>>>>>>>> scsi_blk : <none>
>>>>>>>>>>>> usb_storage_blk : <none>
>>>>>>>>>>>> virtio-blk : <none>
>>>>>>>>>>>>
>>>>>>>>>>>> So a efi_blk device was mistaken for a host device.
>>>>>>>>>>>>
>>>>>>>>>>>> I continue with
>>>>>>>>>>>>
>>>>>>>>>>>> => host bind 0 ../sandbox.img
>>>>>>>>>>>> => ls host 0:1
>>>>>>>>>>>>
>>>>>>>>>>>> and get the following output:
>>>>>>>>>>>>
>>>>>>>>>>>> 13 hello.txt
>>>>>>>>>>>> 7 u-boot.txt
>>>>>>>>>>>>
>>>>>>>>>>>> 2 file(s), 0 dir(s)
>>>>>>>>>>>>
>>>>>>>>>>>> This is the content of efiblock 0:1 and not of host 0:1 (sic!).
>>>>>>>>>>>>
>>>>>>>>>>>> The uclass of the parent device is irrelevant for the
>>>>>>>>>>>> determination of the
>>>>>>>>>>>> uclass of the block device. We must use the uclass stored in the
>>>>>>>>>>>> block
>>>>>>>>>>>> device descriptor.
>>>>>>>>>>>>
>>>>>>>>>>>> This issue has been raised repeatedly:
>>>>>>>>>>>>
>>>>>>>>>>>> [PATCH 1/1] block: fix blk_get_devnum_by_typename()
>>>>>>>>>>>> https://lore.kernel.org/u-boot/20220802094933.69170-1-heinrich.schuchardt@canonical.com/
>>>>>>>>>>>> [PATCH 1/1] blk: simplify blk_get_devnum_by_typename()
>>>>>>>>>>>> https://lore.kernel.org/u-boot/20211023140647.7661-1-heinrich.schuchardt@canonical.com/
>>>>>>>>>>>
>>>>>>>>>>> Yes and you were not able/willing to take on the required work, so
>>>>>>>>>>> this carried on longer than it should have. I finally did this myself
>>>>>>>>>>> and it is now in -next.
>>>>>>>>>>
>>>>>>>>>> The refactoring was orthogonal to the problem that I reported and
>>>>>>>>>> which
>>>>>>>>>> you unfortunately did not consider in the process.
>>>>>>>>>
>>>>>>>>> Well it involved using if_type to work around a problem, just making
>>>>>>>>> it harder to get rid of. Overall I am in favour of a faster pace of
>>>>>>>>> migration that we have been following and it would help if people took
>>>>>>>>> on some of this, instead of fixing their little issue.
>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> So we might finally be able to fix this problem properly, since
>>>>>>>>>>> if_type is mostly just a work-around concept in -next, with just the
>>>>>>>>>>> fake uclass_id being used at present.
>>>>>>>>>>>
>>>>>>>>>>> Can you use if_type_to_uclass_id() here, which is the work-around
>>>>>>>>>>> function for now?
>>>>>>>>>>
>>>>>>>>>> This function does not exist in origin/next. We won't apply this patch
>>>>>>>>>> in the 2022-10 cycle.
>>>>>>>>>
>>>>>>>>> I think I mean conv_uclass_id() which is the new name.
>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Let's fix the bug first before thinking about future refactoring.
>>>>>>>>>>
>>>>>>>>>> You may determine the uclass ID for field bdev in struct blk_desc
>>>>>>>>>> using
>>>>>>>>>> function device_get_uclass_id() when refactoring.
>>>>>>>>>
>>>>>>>>> So if you call conv_uclass_id() (without any other refactoring) does
>>>>>>>>> that fix the problem?
>>>>>>>>
>>>>>>>> Except for UCLASS_USB that function is a NOP. How could it help to
>>>>>>>> differentiate between devices with the same parent device?
>>>>>>>
>>>>>>> It can't. But the root node should not have UCLASS_BLK children. I
>>>>>>> think I mentioned that a few months back?
>>>>>>>
>>>>>>>>
>>>>>>>> Would you agree that blk_get_devnum_by_uclass_idname() should not look
>>>>>>>> at the parent but on the actual device?
>>>>>>>
>>>>>>> No, looking at the parent is exactly what it should do. A block device
>>>>>>> is generic, to the extent possible. Its methods are implemented in the
>>>>>>> parent uclass and are tightly bound to it. See for example
>>>>>>> U_BOOT_DRIVER(mmc_blk) in the MMC uclass.
>>>>>>
>>>>>> Let's look at an MMC device
>>>>>>
>>>>>> root_driver/soc/mmc at 1c0f000/mmc at 1c0f000.blk is a block device.
>>>>>>
>>>>>> What do we need to find out that it can be addressed as mmc 0? The
>>>>>> driver is mmc_blk and its index is 0. We don't need any information
>>>>>> about the parent device at all.
>>>>
>>>> If blk is the MMC block device, the fact that is mmc 0 is determined
>>>> by dev_seq(dev_get_parent(blk)). We are not parsing strings to find
>>>> that out. It is part of the design.
>>>>
>>>>>>
>>>>>>>
>>>>>>> Unfortunately this confusion is my fault since I used the root device
>>>>>>> for the sandbox block devices. That was a convenience and a way to
>>>>>>> reduce somewhat the crushing load of driver model migration. But the
>>>>>>> time for that convenience is gone and we should create a sandbox host
>>>>>>> parent node for the sandbox block devices and tidy up EFI too.
>>>>>>
>>>>>> The only confusion is in the current blk_get_devnum_by_uclass_idname()
>>>>>> code looking into the parent device.
>>>>>>
>>>>>> The parent device is totally irrelevant here. Stop using it.
>>>>
>>>> See below.
>>>>
>>>>>
>>>>> You already noted when writing conv_uclass_id() that using the uclass
>>>>> name does not work properly to find out the CLI name of a devie.
>>>>>
>>>>> Can we put the CLI name for device types ("mmc", "scsi" ...) into struct
>>>>> blk_ops? Then we have a clear separation of the block device from the
>>>>> parent device.
>>>>
>>>> There really isn't any separation in driver model...the parent device
>>>> does determine the type of the block device. It creates the block
>>>> device, using its own uclass. See for example mmc-uclass.c in
>>>> mmc_bind():
>>>>
>>>> ret = blk_create_devicef(dev, "mmc_blk", "blk", UCLASS_MMC,
>>>> dev_seq(dev), 512, 0, &bdev);
>>>>
>>>> The following fields in blk_desc will be dropped at some point:
>>>>
>>>> - uclass_id since it is the same as the parent*
>>>> - bdev (point to block device) since we will stop passing around
>>>> blk_desc and will use the block device instead
>>>> - devnum since it is the save as dev_seq(blk)
>>>>
>>>> * Except for the USB weirdness in conv_uclass_id() which we need to fix
>>>>
>>>> Why do you want this 'separation'? Is this another strange EFI thing
>>>> due to it not using driver model properly?
>>>>
>>>> Also you have not yet replied to my point about needing to create a
>>>> parent 'media' device for every block device. That is also part of the
>>>> design. Have you done that for EFI, or is your reluctance to do that
>>>> behind continued discussions and misalignments on UCLASS_BLK ?
>>>
>>> If I look at physical devices for MMC I might find:
>>>
>>> SoC -> PCI root -> MMC controller -> SD card
>>>
>>> What you call MMC parent device is the MMC controller.
>>>
>>> This is also what can easily modeled as a device path in EFI.
>>
>> OK good. That covers all devices in U-Boot present, I believe.
>>
>>>
>>> In the case of an iSCSI drive provided by iPXE U-boot would provide a
>>> network device which currently has a device path VenHW(root)/MAC().
>>>
>>> iPXE creates a virtual network card VenHW(root)/MAC()/MAC() consuming
>>> the services of the physical one.
>>>
>>> Next it creates a virtual device VenHW(root)/MAC()/MAC()/IPv6() which
>>> exposes the block IO protocol for reading the iSCSI drive.
>>>
>>> The parent for the block device in the EFI world is a network interface.
>>> But the block operations are provided by the block IO protocol which is
>>> provided by the virtual device that iPXE has created and not by a
>>> network interface. So the parent is irrelevant here.
>>
>> Then the virtual device should be the parent? Are we trying to skip
>> one level of hierarchy?
>
> +1
> IMO, the virtual device is a handle (in UEFI term) of UEFI application,
> i.e. iPXE since it actually implements and provides block IO protocol.
>
> In this sense, I don't think that the current implementation of efi_driver
> is appropriate.
> (I mentioned this in the past.)
>
> What I'm not sure, however, is whether the network device card should
> be a *parent* of the application because application may potentially
> implement functionality other than block IO using another device.
>
> Furthermore, what I don't understand yet is what the hierarchy of DM tree
> means for parent-children relationship other than block device case.
>
> -Takahiro Akashi
>
>>>
>>> Sure you could create a single root2 device as parent for all efi_loader
>>> devices like you have root for the host devices. But such a device would
>>> have no functionality at all except carrying a dummy Uclass to store the
>>> CLI string "efiblk" for all of its children.
>>
>> I don't think it should be a root2 device. It should really be a child
>> of the network device, so far as I understand what you have written
>> above.
>>
>>>
>>> Why can't we have the CLI string for the device type in the driver's
>>> struct blk_ops?
>>
>> It isn't just about the CLI string. It's also about having a sensible
>> device hierarchy with 'dm tree', being able to put things in the
>> device tree in a sensible way, etc. This feels like a symptom of the
>> lack of alignment between EFI and driver model.
The hierarchy in UEFI is defined by the device paths installed on the
handles.
Nothing stops a UEFI application to create a first handle with device
path /a and a second with /a/b/c without creating /a/b. It could even
create /a after /a/b/c. An EFI application can legally remove or replace
a device path. So a device /a could suddenly become /a/b/c/d or /e/f.
This makes tracking the EFI's hierarchy in DM fruitless.
On the other hand we would be able to create a device path and handle
for each device originating in U-Boot.
Best regards
Heinrich
>>
>> +Ilias Apalodimas please do see if you can help here.
>>
>> Regards,
>> Simon
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