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

[AKASHI Takahiro <takahiro.akashi@linaro.org>]

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

So I hope that *your* discussion doesn't make any difference to my patch.
Right?

-Takahiro Akashi


> Regards,
> Simon