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

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

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"

---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.

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