Hi, On Mon, 8 Nov 2021 at 11:45, Ilias Apalodimas <ilias.apalodi...@linaro.org> wrote: > > Hi chiming in a little late but > > On Mon, 8 Nov 2021 at 06:46, AKASHI Takahiro <takahiro.aka...@linaro.org> > wrote: > > > > On Fri, Nov 05, 2021 at 10:12:16AM -0600, Simon Glass wrote: > > > Hi Takahiro, > > > > > > On Thu, 4 Nov 2021 at 20:49, AKASHI Takahiro <takahiro.aka...@linaro.org> > > > wrote: > > > > > > > > On Thu, Nov 04, 2021 at 08:02:05PM -0600, Simon Glass wrote: > > > > > Hi, > > > > > > > > > > On Tue, 2 Nov 2021 at 01:43, Heinrich Schuchardt <xypron.g...@gmx.de> > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > > > On 11/1/21 03:14, Simon Glass wrote: > > > > > > > Hi Takahiro, > > > > > > > > > > > > > > On Sun, 31 Oct 2021 at 19:52, AKASHI Takahiro > > > > > > > <takahiro.aka...@linaro.org> wrote: > > > > > > >> > > > > > > >> 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. > > > > > > > > > > > > > > I think we are all a bit unsure. > > > > > > > > > > > > > > I think BLK devices can have children, sorry if I said the wrong > > > > > > > thing > > > > > > > somewhere along the way. For example, a partition would be under > > > > > > > a BLK > > > > > > > device, or a FS. > > > > > > > > > > > > > >> What should DM represent in U-Boot world? > > > > > > > > > > > > > > That is what we are trying to figure out. > > > > > > > > > > > > > > I think the minimum is to have a a way to represent partitions > > > > > > > (s/w > > > > > > > and hw/). As I understand it, that's what we've been discussing. > > > > > > > > > > > > The discovery of hardware partitions is specific to the block device > > > > > > controller SCSI/MMC/ATA/NVMe. We currently do not provide any > > > > > > manipulation commands to create hardware partitions (e.g. NVMe > > > > > > namespaces, SCSI LUNs). This is why extracting a uclass for hardware > > > > > > partitions does not seem necessary. > > > > > > > > > > I can see the reasoning here. It might not stand the test of time but > > > > > how about we go with it for now? For MMC hardware partition we would > > > > > just end up with multiple BLK devices, like we do with SCSI LUNs at > > > > > present, which seems like it should work (with some code tweaks). > > > > > > > > > > > > > > > > > Software partitioning (MBR, GPT, ...) is independent of the > > > > > > harboring > > > > > > block device. > > > > > > > > > > > > We already have a set of drivers for software partition tables in > > > > > > disk/. > > > > > > Currently the available methods of the drivers are defined in > > > > > > U_BOOT_PART_TYPE referring to struct part_driver. > > > > > > > > > > > > Currently struct part_driver knows only the following methods: > > > > > > > > > > > > - get_info() > > > > > > - print() > > > > > > - test() > > > > > > > > > > > > These drivers should be ome a uclass. > > > > > > > > > > > > gpt.c and mbr.c allow to create and delete partitions. I think we > > > > > > should add > > > > > > > > > > > > - create_partition() > > > > > > - delete_partition() > > > > > > > > > > > > to the uclass methods. > > > > > > > > > > That sounds good to me, although since it is a partition uclass, we > > > > > can just use create() and delete(). > > > > > > > > I don't know why we need a "partition table" device in the middle > > > > of DM hierarchy. > > > > I believe that it simply makes the view of DM tree complicated > > > > without any explicit benefit. > > > > > > Well we clearly have an API here. The partition uclass can: > > > > > > - hold the partition table in dev_get_uclass_priv() > > > - support a read() operation to read the partition > > > - support create() to rewrite the partition table > > > - support delete() to overwrite/erase the partition table > > > > > > Then it means that filesystems have the partition table as a parent > > > (unless they are whole-device filesystems), which makes sense > > > > > > So that's why I like the idea. > > > > > > Other than the extra complexity, is there anything else wrong with it? > > > > - First of all, a partition table doesn't look like a 'device' at all. > > - Second, a partition table is just static data for block devices. > > IMO, even if we want to have this data, we can simply hold it > > as some sort of attribute of the device, or maybe as a 'tag' which > > I will introduce in the next version. > > > > -Takahiro Akashi > > > > I don't know how this affect the code, but I agree with Akashi-san > here. It's indeed useful to keep the partition table stored > somewhere, but I think not showing them as part of the device tree is > more intuitive.
Well I think I'm easy either way. I just thought that Heinrich made a good case for having a partition uclass. But as Takahiro says, we can use a tag to attach the partition table to the device. But it should be attached to the device's children (the BLK device) not the media device itself, right? Regards, Simon
