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. Best regards Heinrich >Regards, >Simon
