Messages in this thread | | | Date | Wed, 4 Dec 2019 11:17:51 +0100 | From | Miquel Raynal <> | Subject | Re: [PATCH v5 4/4] mtd: Add driver for concatenating devices |
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Hi Vignesh,
Vignesh Raghavendra <vigneshr@ti.com> wrote on Wed, 4 Dec 2019 15:28:46 +0530:
> Hi Miquel, > > On 27/11/19 4:25 pm, Miquel Raynal wrote: > > Introduce a generic way to define concatenated MTD devices. This may > > be very useful in the case of ie. stacked SPI-NOR. Partitions to > > concatenate are described in an additional property of the partitions > > subnode: > > > > flash0 { > > partitions { > > compatible = "fixed-partitions"; > > part-concat = <&flash0_part1>, <&flash1_part0>; > > > > part0@0 { > > label = "part0_0"; > > reg = <0x0 0x800000>; > > }; > > > > flash0_part1: part1@800000 { > > label = "part0_1"; > > reg = <0x800000 0x800000>; > > }; > > }; > > }; > > IIUC flash0 and flash1 are subnodes of a SPI master node? > And I believe flash0 node's compatible is "jedec,spi-nor"?
Indeed this is one possibility (probably the most common) but in theory this should work for any kind of MTD device, hence I voluntarily dropped the hardware-specific properties to focus on the partitions description here.
> > > > > > flash1 { > > partitions { > > compatible = "fixed-partitions"; > > > > flash0_part1: part1@0 { > > s/flash0_part1/flash1_part0?
Right!
> > > label = "part1_0"; > > reg = <0x0 0x800000>; > > }; > > > > part0@800000 { > > label = "part1_1"; > > reg = <0x800000 0x800000>; > > }; > > }; > > }; > > > > For my understanding, how many /dev/mtdX entries would this create?
If the master is retained (Kconfig option) and thanks to the common partitioning scheme, we would have: * flash0 (mtd0) * part0_0 (mtd1) * part0_1 (mtd2) * flash1 (mtd3) * part1_0 (mtd4) * part1_1 (mtd5)
If we enable this driver, we would also get an additional device: * mtd2-mtd4-concat (or part0_1-part1_0-concat, I don't recall the exact name) being mtd6.
Thanks, Miquèl
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