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Mon, 01 Nov 2021 18:43:00 -0700 (PDT) Received: from laputa ([2400:4050:c3e1:100:a475:65cc:d4b7:aaf5]) by smtp.gmail.com with ESMTPSA id k14sm14316614pga.65.2021.11.01.18.42.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 01 Nov 2021 18:42:59 -0700 (PDT) Date: Tue, 2 Nov 2021 10:42:55 +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: <20211102014255.GA96305@laputa> Mail-Followup-To: AKASHI Takahiro , Simon Glass , Heinrich Schuchardt , Tom Rini , U-Boot Mailing List , Ilias Apalodimas , Alex Graf References: <111f3160-3b5e-302e-c0ca-86c66093207e@gmx.de> <20211029061556.GD33977@laputa> <20211101003600.GB25300@laputa> <20211101015155.GC25300@laputa> 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 Sun, Oct 31, 2021 at 08:14:13PM -0600, 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. I don't still understand why we need a "partition table" device in DM tree. As I proposed in my message on Oct 28th, the hierarchy like - MMC (bus controller) |- BLK (device/hw partition:user data) ||- DISK (partition 0 == a whole device) ||- DISK (partition 1) ||- DISK (partition 2) ||- DISK (partition 3) |- BLK (device/hw partition:boot0) ||- DISK (partition 0 == a whole device) |- BLK (device/hw partition:boot0) ||- DISK (partition 0 == a whole device) |- BLK (device/hw partition:rpmb) -- this is NOT a 'block' device, though. ||- DISK (partition 0 == a whole device) is good enough to represent the partition relationships, ie. BLK-DISK for s/w partition MMC-BLK for h/w partition If you don't like the name DISK (or UCLASS_PARTITION in my RFC), it can be BLK_PARTITION ore even be transformed to BLK with (new) IF_TYPE_PARTITION. (I'd rather prefer to rename BLK->BLK_MEDIA and DISK->BLK, but don't stick to this idea.) Please remember UCLASS_PARTITION devices hold partition information (offset and size) and we don't need to scan the disk every time to access. Currently, UCLASS_MMC doesn't support h/w partitions as standalone BLK devices, but we can manage to modify the drivers. (In this sense, it is much preferable to have a "h/w partition table" device in DM tree, rather than "s/w table", as the former represents a real "hardware" device. -Takahiro Akashi > Regards, > Simon > > > > > > > > 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