[PATCH v3 0/3] mtd concat device driver

From: Bernhard Frauendienst
Date: Sat Sep 08 2018 - 09:14:12 EST

Hi everybody,

my router firmware concatenates two identical flash chips into a single
mtd using mtd_concat_create(), and sets up partitions in a way where one
of them crosses the chip boundary. When porting OpenWRT support for the
board from a mach-file based setup to a device-tree based one, I found
that there is no generic way to create a mtd_concat device from within
the dts. The following patches attempt to provide that possibility.

This is a third roll of that patch series, the first one can be seen at
[1]. The second one [2] was a blunder of my own making. Apologies for
not being able to address the correct recipients two times in a row.

In the first discussion, concerns were raised that a driver for a
"virtual" device like this might have no place in the device tree
system. However, I would argue that specifying a composite device is
very similar to specifying the partitions of a mtd, which can also done
in the device tree. In fact, I believe this is the only way to be able
to specify the partitions of such a concat device in the dts file (but
I'm happy to be corrected if I'm mistaken).
I have made the example in the dt-binding documentation a bit more
expressive in this detail.

In the second roll I have also addressed all issues that reviewers have
brought up so far, hopefully to their satisfaction. These were mainly
whitespace fixes and improved comments.

Best regards,

[1] http://lists.infradead.org/pipermail/linux-mtd/2018-September/083832.html
[2] https://lkml.org/lkml/2018/9/7/1015

Bernhard Frauendienst (3):
mtd: core: add get_mtd_device_by_node
dt-bindings: add bindings for mtd-concat devices
mtd: mtdconcat: add dt driver for concat devices

.../devicetree/bindings/mtd/mtd-concat.txt | 36 +++++
drivers/mtd/Kconfig | 2 +
drivers/mtd/Makefile | 3 +
drivers/mtd/composite/Kconfig | 12 ++
drivers/mtd/composite/Makefile | 6 +
drivers/mtd/composite/virt_concat.c | 128 ++++++++++++++++++
drivers/mtd/mtdcore.c | 38 ++++++
include/linux/mtd/mtd.h | 2 +
8 files changed, 228 insertions(+)
create mode 100644 Documentation/devicetree/bindings/mtd/mtd-concat.txt
create mode 100644 drivers/mtd/composite/Kconfig
create mode 100644 drivers/mtd/composite/Makefile
create mode 100644 drivers/mtd/composite/virt_concat.c