Re: [RFC 01/22] part: call part_init() in blk_get_device_by_str() only for MMC

AKASHI Takahiro
2021-10-13T01:50:23Z

On Tue, Oct 12, 2021 at 03:30:26PM +0200, Heinrich Schuchardt wrote:
>
>
> On 10/12/21 05:26, AKASHI Takahiro wrote:
> > Simon, Heinrich,
> >
> > On Mon, Oct 11, 2021 at 10:14:02AM -0600, Simon Glass wrote:
> > > Hi Heinrich,
> > >
> > > On Mon, 11 Oct 2021 at 09:09, Heinrich Schuchardt <xypron.glpk@gmx.de> wrote:
> > > >
> > > >
> > > >
> > > > On 10/11/21 16:32, Simon Glass wrote:
> > > > > Hi Heinrich,
> > > > >
> > > > > On Mon, 11 Oct 2021 at 04:07, Heinrich Schuchardt <xypron.glpk@gmx.de> wrote:
> > > > > >
> > > > > >
> > > > > >
> > > > > > On 10/1/21 13:48, Peter Robinson wrote:
> > > > > > > On Fri, Oct 1, 2021 at 6:03 AM AKASHI Takahiro
> > > > > > > <takahiro.akashi@linaro.org> wrote:
> > > > > > > >
> > > > > > > > In blk_get_device_by_str(), the comment says: "Updates the partition table
> > > > > > > > for the specified hw partition."
> > > > > > > > Since hw partition is supported only on MMC, it makes no sense to do so
> > > > > > > > for other devices.
> > > > > > >
> > > > > > > Is it not also supported on UFS, and I believe it may also be an
> > > > > > > option in the NVME spec too.
> > > > > >
> > > > > > An NVMe device may expose multiple namespaces. blk_create_devicef() is
> > > > > > called for each namespace.
> > > > > >
> > > > > > A SCSI device may have multiple LUNs. blk_create_devicef() is called for
> > > > > > each LUN.
> > > > > >
> > > > > > This is what the tree shown by 'dm tree' with on NVMe namespace and one LUN.
> > > > > >
> > > > > > Class Index Driver Name
> > > > > > ---------------------------------------------------------------------
> > > > > > root 0 root_driver root_driver
> > > > > > simple_bus 0 simple_bus |- soc
> > > > > > spi 1 sifive_spi | |- spi@10050000
> > > > > > mmc 0 mmc_spi | | `- mmc@0
> > > > > > blk 0 mmc_blk | | `- mmc@0.blk
> > > > > > pci 0 pcie_sifive | |- pcie@e00000000
> > > > > > pci 1 pci_bridge_drv | | `- pci_0:0.0
> > > > > > pci 2 pci_bridge_drv | | `- pci_1:0.0
> > > > > > pci 5 pci_bridge_drv | | |- pci_2:3.0
> > > > > > ahci 0 ahci_pci | | | `- ahci_pci
> > > > > > scsi 0 ahci_scsi | | | `- ahci_scsi
> > > > > > blk 2 scsi_blk | | | `- ahci_scsi.id0lun0
> > > > > > pci 6 pci_bridge_drv | | |- pci_2:4.0
> > > > > > nvme 0 nvme | | | `- nvme#0
> > > > > > blk 1 nvme-blk | | | `- nvme#0.blk#1
> > > > > >
> > > > > > Namespaces and LUNs are modeled as block devices (class = 'blk').
> > > > >
> > > > > So multiple block devices per NVMe device? I did not know that was supported.
> > > > >
> > > > > We need a sandbox driver for NVMe as it has no tests at present. Since
> > > > > it has no tests, I don't think we can expect people to know how to
> > > > > maintain whatever functionality is there.
> > > >
> > > > NVMe drives with multiple namespaces exist for servers but not for
> > > > consumer NVMe drives.
> > > >
> > > > In QEMU you can define an NVMe device with multiple namespaces. Cf.
> > > > https://qemu.readthedocs.io/en/latest/system/devices/nvme.html?highlight=namespace#additional-namespaces
> > > >
> > > > So for a first glimpse at the handling I suggest to use QEMU.
> > >
> > > Well that's fine, but every uclass must have a test and a sandbox
> > > emulator as well.
> >
> > Wait, it seems that you're discussing a different thing from my patch.
> >
> > While I don't know whether NVMe namespaces are a kind of "HW partitions",
> > we don't care much here as long as any namespace can be handled simply
> > as a normal block device, like scsi LUN's, in terms of U-Boot driver model.
> >
> > # On the other hand, we have to explicitly switch "hw partitions"
> > # with blk_select_hwpart_devnum() on MMC devices even though we use
> > # the *same* udevice(blk_desc).
> > # See do_mmcrpmb() in cmd/mmc.c
>
> Each hardware partition should be a block device (class blk) which is
> mirrored in the UEFI world by a CTRL() device.

Yes, whether it is mirrored or not, a hw partition is to be
a separate udevice from its associated raw device.

> It is not necessary for
> parent device to be a block device.

I'm not sure what 'parent device' means here, but I guess that it is
the raw MMC device (as a controller handle in UEFI terminology which
is set to provide BLOCK_IO_PROTOCOL), isn't it?

-Takahiro Akashi

> Best regards
>
> Heinrich
>
> >
> > So I hope that *your* discussion doesn't make any difference to my patch.
> > Right?
> >
> > -Takahiro Akashi
> >
> >
> > > Regards,
> > > Simon