Hi Heinrich, On Sat, 13 Nov 2021 at 11:42, Heinrich Schuchardt <xypron.g...@gmx.de> wrote: > > Am 13. November 2021 19:14:32 MEZ schrieb Simon Glass <s...@chromium.org>: > >Hi, > > > >On Mon, 8 Nov 2021 at 17:09, Simon Glass <s...@chromium.org> wrote: > >> > >> 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? > > > >As there has been no discussion in 5 days and Takahiro is writing > >this, let's go with no uclass for the partition table. > > > > Without uclass you cannot bring the partition table drivers into th driver > model. > > No clue what a tag should be in the driver model.
A tag is a way to associate data with a device. At present we do this with varoius built-in mechanisms (priv data, uclass-priv, plat, etc.) but with tags you can add something else. Regards, Simon
