Re: [PATCH v5 4/4] mtd: Add driver for concatenating devices

Vignesh Raghavendra
2019-12-04T12:55:49Z

On 04/12/19 3:47 pm, Miquel Raynal wrote:
> Hi Vignesh,
>
> Vignesh Raghavendra <vigneshr@ti.com> wrote on Wed, 4 Dec 2019 15:28:46
> +0530:
>
[...]
>> 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.
>

Ah, make sense...

>>
>>
>>>
>>> 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.

Ok, thanks for the clarification!

--
Regards
Vignesh