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Thu, 04 Nov 2021 19:49:33 -0700 (PDT) Received: from laputa ([2400:4050:c3e1:100:844c:5534:2811:8a4d]) by smtp.gmail.com with ESMTPSA id lb4sm2326791pjb.18.2021.11.04.19.49.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Nov 2021 19:49:33 -0700 (PDT) Date: Fri, 5 Nov 2021 11:49:29 +0900 From: AKASHI Takahiro To: Simon Glass Cc: Heinrich Schuchardt , Tom Rini , U-Boot Mailing List , Ilias Apalodimas , Alex Graf Subject: Re: [RFC 07/22] dm: blk: add UCLASS_PARTITION Message-ID: <20211105024929.GD27316@laputa> Mail-Followup-To: AKASHI Takahiro , Simon Glass , Heinrich Schuchardt , Tom Rini , U-Boot Mailing List , Ilias Apalodimas , Alex Graf References: <20211029061556.GD33977@laputa> <20211101003600.GB25300@laputa> <20211101015155.GC25300@laputa> <3b96557b-ff89-19e0-e250-200dc19eb93d@gmx.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-BeenThere: u-boot@lists.denx.de X-Mailman-Version: 2.1.34 Precedence: list List-Id: U-Boot discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: u-boot-bounces@lists.denx.de Sender: "U-Boot" X-Virus-Scanned: clamav-milter 0.103.2 at phobos.denx.de X-Virus-Status: Clean On Thu, Nov 04, 2021 at 08:02:05PM -0600, Simon Glass wrote: > Hi, > > On Tue, 2 Nov 2021 at 01:43, Heinrich Schuchardt wrote: > > > > > > > > On 11/1/21 03:14, Simon Glass wrote: > > > Hi Takahiro, > > > > > > On Sun, 31 Oct 2021 at 19:52, AKASHI Takahiro > > > 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 > > >>> 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 : > > >>>>>> Hi, > > >>>>>> > > >>>>>> On Fri, 29 Oct 2021 at 13:26, Heinrich Schuchardt wrote: > > >>>>>>> > > >>>>>>> > > >>>>>>> > > >>>>>>> Am 29. Oktober 2021 08:15:56 MESZ schrieb AKASHI Takahiro : > > >>>>>>>> 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. -Takahiro Akashi > > > > The partitions handled by cmd/mtdparts.c, cmd/nand.c are also software > > partitions. The difference to MBR, GPT is that the partition table is > > held in memory and not on disk. These partitions could be modeled in the > > same uclass. > > For future work! > > 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