Re: [RFC 07/22] dm: blk: add UCLASS_PARTITION

Simon Glass
2021-10-14T20:55:58Z

Hi Takahiro,

On Thu, 14 Oct 2021 at 02:03, AKASHI Takahiro
<takahiro.akashi@linaro.org> wrote:
>
> Simon,
>
> On Wed, Oct 13, 2021 at 12:05:58PM -0600, Simon Glass wrote:
> > Hi Takahiro,
> >
> > On Tue, 12 Oct 2021 at 19:32, AKASHI Takahiro
> > <takahiro.akashi@linaro.org> wrote:
> > >
> > > On Tue, Oct 12, 2021 at 11:14:17AM -0400, Tom Rini wrote:
> > > > On Mon, Oct 11, 2021 at 10:14:00AM -0600, Simon Glass wrote:
> > > > > Hi Heinrich,
> > > > >
> > > > > On Mon, 11 Oct 2021 at 09:02, Heinrich Schuchardt <xypron.glpk@gmx.de> wrote:
> > > > > >
> > > > > >
> > > > > >
> > > > > > On 10/11/21 16:54, Simon Glass wrote:
> > > > > > > Hi Takahiro,
> > > > > > >
> > > > > > > On Sun, 10 Oct 2021 at 20:29, AKASHI Takahiro
> > > > > > > <takahiro.akashi@linaro.org> wrote:
> > > > > > >>
> > > > > > >> Heinrich,
> > > > > > >>
> > > > > > >> On Fri, Oct 08, 2021 at 10:23:52AM +0200, Heinrich Schuchardt wrote:
> > > > > > >>>
> > > > > > >>>
> > > > > > >>> On 10/8/21 02:51, AKASHI Takahiro wrote:
> > > > > > >>>> On Mon, Oct 04, 2021 at 12:27:59PM +0900, AKASHI Takahiro wrote:
> > > > > > >>>>> On Fri, Oct 01, 2021 at 11:30:37AM +0200, Heinrich Schuchardt wrote:
> > > > > > >>>>>>
> > > > > > >>>>>>
> > > > > > >>>>>> On 10/1/21 07:01, AKASHI Takahiro wrote:
> > > > > > >>>>>>> UCLASS_PARTITION device will be created as a child node of
> > > > > > >>>>>>> UCLASS_BLK device.
> > > > > > >>>>>>>
> > > > > > >>>>>>> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> > > > > > >>>>>>> ---
> > > > > > >>>>>>> drivers/block/blk-uclass.c | 111 +++++++++++++++++++++++++++++++++++++
> > > > > > >>>>>>> include/blk.h | 9 +++
> > > > > > >>>>>>> include/dm/uclass-id.h | 1 +
> > > > > > >>>>>>> 3 files changed, 121 insertions(+)
> > > > > > >>>>>>>
> > > > > > >>>>>>> diff --git a/drivers/block/blk-uclass.c b/drivers/block/blk-uclass.c
> > > > > > >>>>>>> index 83682dcc181a..dd7f3c0fe31e 100644
> > > > > > >>>>>>> --- a/drivers/block/blk-uclass.c
> > > > > > >>>>>>> +++ b/drivers/block/blk-uclass.c
> > > > > > >>>>>>> @@ -12,6 +12,7 @@
> > > > > > >>>>>>> #include <log.h>
> > > > > > >>>>>>> #include <malloc.h>
> > > > > > >>>>>>> #include <part.h>
> > > > > > >>>>>>> +#include <string.h>
> > > > > > >>>>>>> #include <dm/device-internal.h>
> > > > > > >>>>>>> #include <dm/lists.h>
> > > > > > >>>>>>> #include <dm/uclass-internal.h>
> > > > > > >>>>>>> @@ -695,6 +696,44 @@ int blk_unbind_all(int if_type)
> > > > > > >>>>>>> return 0;
> > > > > > >>>>>>> }
> > > > > > >>>>>>>
> > > > > > >>>>>>> +int blk_create_partitions(struct udevice *parent)
> > > > > > >>>>>>> +{
> > > > > > >>>>>>> + int part, count;
> > > > > > >>>>>>> + struct blk_desc *desc = dev_get_uclass_plat(parent);
> > > > > > >>>>>>> + struct disk_partition info;
> > > > > > >>>>>>> + struct disk_part *part_data;
> > > > > > >>>>>>> + char devname[32];
> > > > > > >>>>>>> + struct udevice *dev;
> > > > > > >>>>>>> + int ret;
> > > > > > >>>>>>> +
> > > > > > >>>>>>> + if (!CONFIG_IS_ENABLED(PARTITIONS) ||
> > > > > > >>>>>>> + !CONFIG_IS_ENABLED(HAVE_BLOCK_DEVICE))
> > > > > > >>>>>>> + return 0;
> > > > > > >>>>>>> +
> > > > > > >>>>>>> + /* Add devices for each partition */
> > > > > > >>>>>>> + for (count = 0, part = 1; part <= MAX_SEARCH_PARTITIONS; part++) {
> > > > > > >>>>>>> + if (part_get_info(desc, part, &info))
> > > > > > >>>>>>> + continue;
> > > > > > >>>>>>> + snprintf(devname, sizeof(devname), "%s:%d", parent->name,
> > > > > > >>>>>>> + part);
> > > > > > >>>>>>> +
> > > > > > >>>>>>> + ret = device_bind_driver(parent, "blk_partition",
> > > > > > >>>>>>> + strdup(devname), &dev);
> > > > > > >>>>>>> + if (ret)
> > > > > > >>>>>>> + return ret;
> > > > > > >>>>>>> +
> > > > > > >>>>>>> + part_data = dev_get_uclass_plat(dev);
> > > > > > >>>>>>> + part_data->partnum = part;
> > > > > > >>>>>>> + part_data->gpt_part_info = info;
> > > > > > >>>>>>> + count++;
> > > > > > >>>>>>> +
> > > > > > >>>>>>> + device_probe(dev);
> > > > > > >>>>>>> + }
> > > > > > >>>>>>> + debug("%s: %d partitions found in %s\n", __func__, count, parent->name);
> > > > > > >>>>>>> +
> > > > > > >>>>>>> + return 0;
> > > > > > >>>>>>> +}
> > > > > > >>>>>>> +
> > > > > > >>>>>>> static int blk_post_probe(struct udevice *dev)
> > > > > > >>>>>>> {
> > > > > > >>>>>>> if (IS_ENABLED(CONFIG_PARTITIONS) &&
> > > > > > >>>>>>> @@ -713,3 +752,75 @@ UCLASS_DRIVER(blk) = {
> > > > > > >>>>>>> .post_probe = blk_post_probe,
> > > > > > >>>>>>> .per_device_plat_auto = sizeof(struct blk_desc),
> > > > > > >>>>>>> };
> > > > > > >>>>>>> +
> > > > > > >>>>>>> +static ulong blk_part_read(struct udevice *dev, lbaint_t start,
> > > > > > >>>>>>> + lbaint_t blkcnt, void *buffer)
> > > > > > >>>>>>> +{
> > > > > > >>>>>>> + struct udevice *parent;
> > > > > > >>>>>>> + struct disk_part *part;
> > > > > > >>>>>>> + const struct blk_ops *ops;
> > > > > > >>>>>>> +
> > > > > > >>>>>>> + parent = dev_get_parent(dev);
> > > > > > >>>>>>
> > > > > > >>>>>> What device type will the parent have if it is a eMMC hardware partition?
> > > > > > >>>>>>
> > > > > > >>>>>>> + ops = blk_get_ops(parent);
> > > > > > >>>>>>> + if (!ops->read)
> > > > > > >>>>>>> + return -ENOSYS;
> > > > > > >>>>>>> +
> > > > > > >>>>>>> + part = dev_get_uclass_plat(dev);
> > > > > > >>>>>>
> > > > > > >>>>>> You should check that we do not access the block device past the
> > > > > > >>>>>> partition end:
> > > > > > >>>>>
> > > > > > >>>>> Yes, I will fix all of checks.
> > > > > > >>>>>
> > > > > > >>>>>> struct blk_desc *desc = dev_get_uclass_plat(parent);
> > > > > > >>>>>> if ((start + blkcnt) * desc->blksz < part->gpt_part_info.blksz)
> > > > > > >>>>>> return -EFAULT.
> > > > > > >>>>>>
> > > > > > >>>>>>> + start += part->gpt_part_info.start;
> > > > > > >>>>
> > > > > > >>>> A better solution is:
> > > > > > >>>> if (start >= part->gpt_part_info.size)
> > > > > > >>>> return 0;
> > > > > > >>>>
> > > > > > >>>> if ((start + blkcnt) > part->gpt_part_info.size)
> > > > > > >>>> blkcnt = part->gpt_part_info.size - start;
> > > > > > >>>> start += part->gpt_part_info.start;
> > > > > > >>>> instead of returning -EFAULT.
> > > > > > >>>> (note that start and blkcnt are in "block".)
> > > > > > >>>
> > > > > > >>> What is your motivation to support an illegal access?
> > > > > > >>>
> > > > > > >>> We will implement the EFI_BLOCK_IO_PROTOCOL based on this function. The
> > > > > > >>> ReadBlocks() and WriteBlocks() services must return
> > > > > > >>> EFI_INVALID_PARAMETER if the read request contains LBAs that are not
> > > > > > >>> valid.
> > > > > > >>
> > > > > > >> I interpreted that 'LBA' was the third parameter to ReadBlocks API,
> > > > > > >> and that if the starting block is out of partition region, we should
> > > > > > >> return an error (and if not, we still want to trim IO request to fit
> > > > > > >> into partition size as other OS's API like linux does).
> > > > > > >> Do you think it's incorrect?
> > > > > > >
> > > > > > > [..]
> > > > > > >
> > > > > > > Related to this patch I think that the partition type should be really
> > > > > > > be a child of the media device:
> > > > > > >
> > > > > > > - MMC
> > > > > > > |- BLK
> > > > > > > |- PARTITION
> > > > > > > |- BLK
> > > > > > > |- PARTITION
> > > > > > > |- BLK
> > > > > > > |- PARTITION
> > > > > > > |- BLK
> > > > > > >
> > > > > > > It seems more natural to me that putting the partitions under the
> > > > > > > top-level BLK device, so that BLK remains a 'terminal' device.
> > > > > > >
> > > > > > > The partition uclass is different from BLK, of course. It could
> > > > > > > contain information about the partition such as its partition number
> > > > > > > and UUID.
> > > > > >
> > > > > > Do you mean hardware partition here? Otherwise I would not know what BLK
> > > > > > should model.
> > > > >
> > > > > I mean that (I think) we should not use BLK to model partitions. A BLK
> > > > > should just be a block device.
> > > > >
> > > > > I don't see any difference between a partition and a hardware
> > > > > partition. We presumably end up with a hierarchy though. Do we need a
> > > > > HWPARTITION uclass so we can handle the hardware partitions
> > > > > differently?
> > > >
> > > > Note that for eMMC devices, hardware partitions are different from
> > > > partition-table partitions. If you boot a system with an eMMC device up
> > > > in Linux you typically get mmcblkN, mmcblkNboot0, mmcblkNboot1 and
> > > > mmcblkNrpmb, each of which are hardware partitions. It gets tricky in
> > > > U-Boot in that you can access each of these with 'mmc dev N M' where M
> > > > defaults to 0 and is the user partition (mmcblkN), 1/2 are boot0/boot1
> > > > and 3 is the rpmb area. The 'mmc' command also allows, when possible
> > > > and implemented, configuring these partitions, again to the extent
> > > > allowed, documented and implemented.
> > >
> > > Thank you. That is exactly what I tried to mention in my reply
> > > at "part: call part_init() in blk_get_device_by_str() only for MMC"
> >
> > OK so it sounds like we agree that hwpartition and partition are
> > different things.
>
> Yes.
> Please note, IIUC, that
> * MMC hw partitions on a device are mapped to one udevice, differentiating
> them by blk_desc->hwpart.
> * Each NVME namespace on a device is mapped to a different udevice with
> a different blk_desc->devnum (and nvme_dev->ns_id).
> * Each UFS partition (or which is, I suppose, equivalent to scsi LUN) on
> a device is mapped to a different udevice with a different blk_desc->devnum
> (and blk_desc->lun).
>
> So even though those type of devices have some kind of hardware partitions,
> they are modelled differently in U-Boot.
> (Obviously, I might be wrong here as I'm not quite familiar yet.)
>
> > >
> > > ---8<---
> > > # 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).
> > > --->8---
> > >
> > > The problem with the current U-Boot driver model is that all of "mmcblkN,
> > > mmcblkNboot0, mmcblkNboot1 and mmcblkNrpmb" will be linked to the same
> > > udevice. We have to do "mmc dev N M" or call blk_select_hwpart[_devnum]()
> > > to distinguish them.
> >
> > Here's our chance to rethink this. What should the device hierarchy be
> > for an MMC device? I made a proposal further up the thread.
>
> Well,
>
> On Mon, Oct 11, 2021 at 11:41:02AM -0600, Simon Glass wrote:
> > On Mon, 11 Oct 2021 at 10:53, Heinrich Schuchardt <xypron.glpk@gmx.de> wrote:
>
> > > >>> [..]
>
> > > >>> Related to this patch I think that the partition type should be really
> > > >>> be a child of the media device:
> > > >>>
> > > >>> - MMC
> > > >>> |- BLK
> > > >>> |- PARTITION
> > > >>> |- BLK
> > > >>> |- PARTITION
> > > >>> |- BLK
> > > >>> |- PARTITION
> > > >>> |- BLK
> > > >>>
> > > >>> It seems more natural to me that putting the partitions under the
> > > >>> top-level BLK device, so that BLK remains a 'terminal' device.
> > > >>>
> > > >>> The partition uclass is different from BLK, of course. It could
> > > >>> contain information about the partition such as its partition number
> > > >>> and UUID.
>
> Yeah, but there is always 1-to-1 mapping between a partition and
> a block (for a partition), so I still wonder whether it makes sense
> to model partitions in the way above.
>
> Alternatively, the following hierarchy also makes some sense.
> (This is not what I have in my RFC though.)
> - MMC
> |- BLK (whole disk with part=0)
> |- BLK (partition 1)
> |- BLK (partition 2)
> |- BLK (partition 3)
>
> or
>
> - MMC
> |- DISK (whole disk)
> ||- BLK (partition 0)
> ||- BLK (partition 1)
> ||- BLK (partition 2)
> ||- BLK (partition 3)
>
> Here
> MMC: provides read/write operations (via blk_ops)
> DISK: holds a geometry of a whole disk and other info
> BLK: partition info (+ blk_ops + geo) (part=0 means a while disk)

Where does this leave hwpart? Are we giving up on that?

Both of these make some sense to me, although I'm not sure what the
second one buys us. Can you explain that? Is it to deal with hwpart?

The name 'disk' is pretty awful though, these days.

If we want to iterate through all the partition tables across all
devices, we could do that with a partition uclass. We could support
different types of partition (s/w and h/w) with the same device
driver.

I think conceptually it is cleaner to have a partition uclass but I do
agree that it corresponds 100% to BLK, so maybe there is little value
in practice. But which device holds the partition table in its
dev_get_priv()?

>
> > > >> Do you mean hardware partition here? Otherwise I would not know what BLK
> > > >> should model.
> > > >
> > > > I mean that (I think) we should not use BLK to model partitions. A BLK
> > > > should just be a block device.
> > >
> > > That is fine. But this implies that a software partition is the child of
> > > a block partition and not the other way round. So the tree should like:
> > >
> > > MMC
> > > |- BLK (user hardware partition)
> > > ||- PARTITION 1 (software partition)
> > > ||- PARTITION 2 (software partition)
> > > |...
> > > ||- PARTITION n (software partition)
> > > |- BLK (rpmb hardware partition)
> > > |- BLK (boot0 hardware partition)
> > > |- BLK (boot1 hardware partition)
> >
> > I presume you meant to include a BLK device under each PARTITION?
> >
> > But anyway, I was more thinking of this:
> >
> > MMC
> > | HWPARTITION rpmb
> > || BLK whole rpmb
> > || PARTITION 1
> > ||| BLK
> > || PARTITION 2
> > ||| BLK
> > || PARTITION 3
>
> Do we have any reason to model a RPMB partition as a block device?
> For linux, at least, mmcblkrpmb looks to be a character device.
>
> > ||| BLK
> > | HWPARTITION boot0
> > || BLK
> > (maybe have PARTITION in here too?
>
> I don't know how boot partitions are used on a production system.
> It's unlikely to have partitions on them given the purpose of "boot"
> partitions?

That's true. So likely they will not be used.

>
> > | HWPARTITION boot1
> > (maybe have PARTITION in here too?
> > || BLK
> >
> > >
> > > >
> > > > I don't see any difference between a partition and a hardware
> > > > partition. We presumably end up with a hierarchy though. Do we need a
> > > > HWPARTITION uclass so we can handle the hardware partitions
> > > > differently?
> > >
> > > Software partitions are defined and discovered via partition tables.
> > > Hardware partitions are defined in a hardware specific way.
> > >
> > > All software partitions map to HD() device tree nodes in UEFI.
> > > An MMC device maps to an eMMC() node
> > > MMC hardware partitions are mapped to Ctrl() nodes by EDK II. We should
> > > do the same in U-Boot.
> > > An SD-card maps to an SD() node.
> > > An NVMe namespace maps to a NVMe() node.
> > > An SCSI LUN maps to a Scsi() node.
> > > SCSI channels of multiple channel controllers are mapped to Ctrl() nodes.
> >
> > I'm not quite sure about the terminology here. I'm not even talking
> > about UEFI, really, just how best to model this stuff in U-Boot.
>
> In UEFI world, each efi_disk has its own device path to identify the device.
> For example, here is a text representation of device path for a scsi disk
> partition:
> /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)/Scsi(0,0)/HD(1,GPT,ce86c5a7-b32a-488f-a346-88fe698e0edc,0x22,0x4c2a)
>
> which is set to be created from a corresponding udevice (more strictly
> blkc_desc + part).
>
> So the issue Heinrich raised here is a matter of implementation of
> this conversion (software partitions, and SCSI channels?) as well as
> a modeling for some device type on U-Boot, i.e. MMC hardware partitions.

Yes I see that. It's just that we should get our house in order first,
since these discussions didn't happen when the EFI layer was written 6
years ago. If we have a good model for partitions (not just block
devices) in U-Boot then it should be easier to map EFI onto it.

Regards,
Simon

>
> -Takahiro Akashi
>
> > In U-Boot, UCLASS_SCSI should be a SCSI controller, not a device,
> > right? I'm a little worried it is not modelled correctly. After all,
> > what is the parent of a SCSI device?
> >
> > >
> > > The simple file protocol is only provided by HD() nodes and not by nodes
> > > representing hardware partitions. If the whole hardware partition is
> > > formatted as a file system you would still create a HD() node with
> > > partition number 0.
> >
> > Regards,
> > Simon
> ---
> >
> > >
> > > When it comes to UEFI, I hope we can currently support hw partitions
> > > in this way:
> > > => efidebug add boot -b 1 FOO mmc 0.1 /foo.bin ""
> > > (".1" is a key, I have never tried this syntax though.)
> > >
> > > But probably its device path won't be properly formatted
> > > as expected as Heinrich suggested.
> > >
> > > -Takahiro Akashi
> > >
> > >
> > > > In terms of modeling, this is akin to how if you use a USB card reader
> > > > that supports 4 different form-factor cards, you can end up with 4
> > > > different devices showing up in Linux (if you have one of the nice card
> > > > readers that supports multiple cards at once).
> > > >
> > > > --
> > > > Tom
> > >
> > >
> >
> > Regards,
> > Simon