linux-kernel - Re: [PATCH v6 2/7] mmc: block: Add mmc_bdev_to

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Date:   Mon, 18 May 2020 09:24:42 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Jens Axboe <axboe@...nel.dk>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        David Heidelberg <david@...t.cz>,
        Peter Geis <pgwipeout@...il.com>,
        Stephen Warren <swarren@...dotorg.org>,
        Nicolas Chauvet <kwizart@...il.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Billy Laws <blaws05@...il.com>,
        Nils Östlund <nils@...tan.com>,
        Christoph Hellwig <hch@...radead.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        Randy Dunlap <rdunlap@...radead.org>,
        linux-tegra <linux-tegra@...r.kernel.org>,
        linux-block <linux-block@...r.kernel.org>,
        Andrey Danin <danindrey@...l.ru>,
        Gilles Grandou <gilles@...ndou.net>,
        Ryan Grachek <ryan@...ted.us>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Steve McIntyre <steve@...val.com>,
        linux-efi <linux-efi@...r.kernel.org>
Subject: Re: [PATCH v6 2/7] mmc: block: Add mmc_bdev_to_card() helper

On Mon, 18 May 2020 at 01:55, Dmitry Osipenko <digetx@...il.com> wrote:
>
> 17.05.2020 05:12, Dmitry Osipenko пишет:
> > NVIDIA Tegra Partition Table takes into account MMC card's BOOT_SIZE_MULT
> > parameter, and thus, the partition parser needs to retrieve that EXT_CSD
> > value from the block device.  There are also some other parts of struct
> > mmc_card that are needed for the partition parser in order to calculate
> > the eMMC offset and verify different things.  This patch introduces new
> > helper which takes block device for the input argument and returns the
> > corresponding MMC card.
> >
> > Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> > ---
> >  drivers/mmc/core/block.c   | 15 +++++++++++++++
> >  include/linux/mmc/blkdev.h | 13 +++++++++++++
> >  2 files changed, 28 insertions(+)
> >  create mode 100644 include/linux/mmc/blkdev.h
> >
> > diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
> > index c5367e2c8487..99298e888381 100644
> > --- a/drivers/mmc/core/block.c
> > +++ b/drivers/mmc/core/block.c
> > @@ -40,6 +40,7 @@
> >  #include <linux/debugfs.h>
> >
> >  #include <linux/mmc/ioctl.h>
> > +#include <linux/mmc/blkdev.h>
> >  #include <linux/mmc/card.h>
> >  #include <linux/mmc/host.h>
> >  #include <linux/mmc/mmc.h>
> > @@ -305,6 +306,20 @@ static ssize_t force_ro_store(struct device *dev, struct device_attribute *attr,
> >       return ret;
> >  }
> >
> > +struct mmc_card *mmc_bdev_to_card(struct block_device *bdev)
> > +{
> > +     struct mmc_blk_data *md;
> > +
> > +     if (bdev->bd_disk->major != MMC_BLOCK_MAJOR)
> > +             return NULL;
> > +
> > +     md = mmc_blk_get(bdev->bd_disk);
> > +     if (!md)
> > +             return NULL;
> > +
> > +     return md->queue.card;
> > +}
> > +
> >  static int mmc_blk_open(struct block_device *bdev, fmode_t mode)
> >  {
> >       struct mmc_blk_data *md = mmc_blk_get(bdev->bd_disk);
> > diff --git a/include/linux/mmc/blkdev.h b/include/linux/mmc/blkdev.h
> > new file mode 100644
> > index 000000000000..67608c58de70
> > --- /dev/null
> > +++ b/include/linux/mmc/blkdev.h
> > @@ -0,0 +1,13 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +/*
> > + *  linux/include/linux/mmc/blkdev.h
> > + */
> > +#ifndef LINUX_MMC_BLOCK_DEVICE_H
> > +#define LINUX_MMC_BLOCK_DEVICE_H
> > +
> > +struct block_device;
> > +struct mmc_card;
> > +
> > +struct mmc_card *mmc_bdev_to_card(struct block_device *bdev);
> > +
> > +#endif /* LINUX_MMC_BLOCK_DEVICE_H */
> >
>
> Hello Ulf / Jens and everyone,

Hi Dmitry,

>
> Guys, what do you think about this change?

As I stated in an earlier reply, I am deferring the review from mmc
point of view, until I see some confirmation from Jens that he is okay
with adding a new partition format.

Otherwise I may just waste my time on reviews. I hope you understand.

Kind regards
Uffe

>
> Currently it's not allowed to compile MMC_BLOCK as a loadable kernel
> module if TEGRA_PARTITION is enabled because it depends on MMC_BLOCK
> presence. I'm curious if this situation could be improved by moving
> mmc_bdev_to_card() to linux/mmc/blkdev.h and then:
>
> 1. Moving all private mmc/core/block.c structs to the public
> linux/mmc/blkdev.h.
>
> 2. Or adding a "private opaque" pointer to a struct block_device and
> setting it to md->queue.card, for example.
>
> 3. I see that struct block_device already has some bd_private field, but
> I'm not sure whether it could be used for what I'm trying to achieve.
> Actually I don't see where bd_private is used in kernel at all.
>
> I'd like get yours feedback, thanks in advance.