On Sun, Oct 31, 2021 at 07:15:17PM -0600, Simon Glass wrote: > Hi Takahiro, > > On Sun, 31 Oct 2021 at 18:36, AKASHI Takahiro > <takahiro.aka...@linaro.org> wrote: > > > > On Sat, Oct 30, 2021 at 07:45:14AM +0200, Heinrich Schuchardt wrote: > > > > > > > > > Am 29. Oktober 2021 23:17:56 MESZ schrieb Simon Glass <s...@chromium.org>: > > > >Hi, > > > > > > > >On Fri, 29 Oct 2021 at 13:26, Heinrich Schuchardt <xypron.g...@gmx.de> > > > >wrote: > > > >> > > > >> > > > >> > > > >> Am 29. Oktober 2021 08:15:56 MESZ schrieb AKASHI Takahiro > > > >> <takahiro.aka...@linaro.org>: > > > >> >On Fri, Oct 29, 2021 at 06:57:24AM +0200, Heinrich Schuchardt wrote: > > > >> >> > > > >> >> > > > >> >> > I agree with Heinrich that we are better to leave BLK as it is, > > > >> >> > both > > > >> >> > in name and meaning. I think maybe I am missing the gist of your > > > >> >> > argument. > > > >> >> > > > > >> >> > If we use UCLASS_PART, for example, can we have that refer to > > > >> >> > both s/w > > > >> >> > and h/w partitions, as Herinch seems to allude to below? What > > > >> >> > would > > > >> >> > the picture look like the, and would it get us closer to > > > >> >> > agreement? > > > >> >> > > > >> >> In the driver model: > > > >> >> > > > >> >> A UCLASS is a class of drivers that share the same interface. > > > >> >> A UDEVICE is a logical device that belongs to exactly one UCLASS > > > >> >> and is > > > >> >> accessed through this UCLASS's interface. > > > >> > > > > >> >Please be careful about "accessed through" which is a quite confusing > > > >> >expression. I don't always agree with this view. > > > >> > > > > >> >> A hardware partition is an object that exposes only a single > > > >> >> interface > > > >> >> for block IO. > > > >> >> > > > >> >> A software partition is an object that may expose two interfaces: > > > >> >> one > > > >> >> for block IO, the other for file IO. > > > >> > > > > >> >Are you talking about UEFI world or U-Boot? > > > >> >Definitely, a hw partitions can provide a file system > > > >> >if you want. > > > >> >It's a matter of usage. > > > >> > > > > >> >I remember that we had some discussion about whether block devices > > > >> >on UEFI system should always have a (sw) partition table or not. > > > >> >But it is a different topic. > > > >> > > > > >> >> The UEFI model does not have a problem with this because on a > > > >> >> handle you > > > >> >> can install as many different protocols as you wish. But U-Boot's > > > >> >> driver > > > >> >> model only allows a single interface per device. Up to now U-Boot > > > >> >> has > > > >> >> overcome this limitation by creating child devices for the extra > > > >> >> interfaces. > > > >> > > > > >> >> We have the following logical levels: > > > >> >> > > > >> >> Controller | Block device | Software Partition| File system > > > >> >> ----------------+--------------+-------------------+------------ > > > >> >> NVMe Drive | Namespace | Partition 1..n | FAT, EXT4 > > > >> >> ATA Controller | ATA-Drive | | > > > >> >> SCSI Controller | LUN | | > > > >> >> MMC Controller | HW-Partition | | > > > >> >> MMC Controller | SD-Card | | > > > >> >> USB-Node | USB-Drive | | > > > >> >> > > > >> >> In the device tree this could be modeled as: > > > >> >> > > > >> >> |-- Controller (UCLASS_CTRL) > > > >> >> | |-- Block device / HW Partition (UCLASS_BLK) (A) > > > >> >> | | |-- Partition table (UCLASS_PARTITION_TABLE) (B) > > > >> >> | | |-- Software Partition (UCLASS_BLK) > > > >> >> | | |-- File system (UCLASS_FS) > > > >> >> | | > > > >> >> | |-- Block device (UCLASS_BLK) > > > >> >> | |-- File system (UCLASS_FS) > > > >> > > > > >> >I don't know why we expect PARTITION_TABLE and FS to appear in DM > > > >> >tree. > > > >> >What is the benefit? > > > >> >(A) and (B) always have 1:1 relationship. > > > >> > > > >> No. You can have a bare device without a partition table. > > > > > > > >I can have a DOS partition that covers the whole device, without a > > > >partition table. This is supported in U-Boot and Linux. > > > > > > > >> > > > >> We have several partition table drivers: DOS, GPT, OSX, ... . In > > > >> future we should also have one for the NOR Flash partitions. All of > > > >> these drivers have a common interface. As the partition table type is > > > >> mostly independent of the block device type we should use separate > > > >> uclasses and udevices. > > > >> > > > >> >I also remember that you claimed that not all efi objects(handles and > > > >> >protocols like SIMPE_FILE_SYSTEM_PROTOCOL) need to have corresponding > > > >> >U-Boot counterparts in our 2019 discussion. > > > >> > > > > >> >If we *need* PARTITION_TALBLE, why don't we have HW_PARTITION_TABLE, > > > >> >which should support other type of hw partitions as well? > > > >> > > > >> How hardware partitions, LUNs, ATA drives are enumerated is specific > > > >> to the type of controller while the type of software partition table > > > >> is independent of the block device. > > > >> > > > >> > > > > >> >|-- eMMC controller (UCLASS_MMC) > > > >> >| |-- eMMC device1 / Physical media (UCLASS_HW_PARTITION_TABLE?) > > > >> >| |-- Block device / HW Partition:user data (UCLASS_BLK) > > > >> >| | |-- Partition table (UCLASS_PARTITION_TABLE) > > > >> >| | |-- Software Partition (UCLASS_BLK) > > > >> >| | |-- File system (UCLASS_FS) > > > >> >| | > > > >> >| |-- Block device / HW Partition:boot0 (UCLASS_BLK) > > > >> >| |-- Block device / HW Partition:boot1 (UCLASS_BLK) > > > >> > ... > > > >> >| |-- eMMC device2 / Physical media (UCLASS_HW_PARTITION_TABLE?) > > > >> > > > > >> >|-- scsi controller (UCLASS_SCSI) > > > >> >| |-- scsi disk / Physical media (UCLASS_HW_PARTITION_TABLE?) > > > >> >| |-- scsi LUN1 (UCLASS_HW_PARTITION_TABLE?) > > > >> >| | |-- Partition table (UCLASS_PARTITION_TABLE) > > > >> >| | |-- Software Partition (UCLASS_BLK) > > > >> >| |-- scsi LUN2 (UCLASS_HW_PARTITION_TABLE?) > > > >> > ... > > > >> > > > > >> >(Here I ignored scsi buses/channels which make things more > > > >> >complicated.) > > > >> > > > > >> >This kind of complex hierarchy doesn't benefit anybody. > > > >> > > > >> All these levels exist already. We simply do not model them yet in the > > > >> DM way. > > > >> > > > >> The device tree depth is the outcome of the udevice exposing always > > > >> only a single interface defined by the uclass. > > > >> > > > >> The UEFI design allows installing multiple protocol interfaces on a > > > >> single handle. This may result in simpler device trees in some cases. > > > > > > > >Yes, the complexity has to go somewhere. With driver model I chose to > > > >have a single interface per uclass, since it is simpler to understand, > > > >no need to request a protocol for a device, etc. > > > > > > > >Our current setup is similar to this > > > > > > > >|-- Controller (UCLASS_MMC) > > > >| |-- Block device (UCLASS_BLK) - 'usual' HW partition > > > >| |-- Block device (UCLASS_BLK) - e.g. for a different HW partition* > > > > > > > >* although I don't think the MMC code actually supports it - SCSI does > > > >though > > > > > > > >We want to add devices for the partition table and the filesystem, so > > > >could do: > > > > > > > >|-- Controller (UCLASS_MMC) > > > >| |-- Block device (UCLASS_BLK) - 'usual' HW partition (the whole > > > >device) > > > >| | |-- Partition table (UCLASS_PART) - DOS partition (or EFI) > > > >| | | |-- Block device (UCLASS_BLK) - partition 1 > > > >| | | | |-- Filesystem (UCLASS_FS) - DOS filesystem > > > >| | | |-- Block device (UCLASS_BLK) - partition 2 > > > >| | | | |-- Filesystem (UCLASS_FS) - ext5 filesystem > > > >| |-- Block device (UCLASS_BLK) - e.g. for a different HW > > > >partition (the whole device) > > > > > > > >This is similar to Heinrich's, but without the top-level > > > >UCLASS_HW_PARTITION_TABLE which I am not sure is necessary. > > > > > > Are further MMC hw partitions, multiple SCSI LUNs and multiple NVME > > > namespaces already treated as separate BLK devices? > > > > Yes. > > What I meant to say is that, if we don't need a partition table 'udevice' > > for hw partitions, we don't need such a device for sw partitions neither. > > > > Meanwhile, what about UCLASS_FS? Why do we need this? > > We don't need it for our current discussion, but if we want to 'open' > the filesystem and keep the metadata around, rather than reading it > again every time we access a file, we might find it useful. Open files > could be children of the FS uclass, perhaps, if we go a step further > and create devices for them.
Do you want to invent linux-like mount-point concepts or procfs? I remember that you didn't want to have child nodes under BLK devices. I'm getting confused about our goal. What should DM represent in U-Boot world? > Regards, > Simon > > > > > > > > >It is compatible with what we have now and we could enable/disable the > > > >extra devices with a Kconfig. > > > > > > > >Regards, > > > >Simon > > > > > > > > > > > > > > > >> > > > > >> >> UCLASS_PARTITION_TABLE would be for the drivers in disk/. > > > >> >> UCLASS_FS would be for the drivers in fs/. > > > >> >> UCLASS_BLK will be for any objects exposing raw block IO. A software > > > >> >> partition does the same. It is created by the partition table > > > >> >> driver as > > > >> >> child of the partition table udevice. > > > >> >> > > > >> >> In this model an eMMC device will not be a UCLASS_BLK device > > > >> >> because it > > > >> >> does not expose block IO. It is the hardware partition that exposes > > > >> >> this > > > >> >> interface. > > > >> >> > > > >> >> The suggested model will allow a clean description of nested > > > >> >> partition > > > >> >> tables. > > > >> >> > > > >> >> In the UEFI world the software partition and its file system must be > > > >> >> mapped to a single handle with device path node type HD(). For the > > > >> >> parent block device we may create a child handle with partition > > > >> >> number 0 > > > >> >> (HD(0)). For the partition table we will not create a handle. > > > >> >> > > > >> >> Best regards > > > >> >> > > > >> >> Heinrich
