[U-Boot] [PATCH] cmd: mtdparts: Probe MTD devices in mtdparts_init()

[Stefan Roese]

On 30.10.18 11:41, Boris Brezillon wrote:
> On Tue, 30 Oct 2018 11:13:37 +0100
> Stefan Roese <sr at denx.de> wrote:
> 
>> Hi Boris,
>>
>> On 30.10.18 11:03, Boris Brezillon wrote:
>>> On Tue, 30 Oct 2018 10:51:51 +0100
>>> Stefan Roese <sr at denx.de> wrote:
>>>    
>>>> Calling "mtdparts" currently fails when its called before any other mtd
>>>> command (or ubi command) has been called. The MTD devices are not
>>>> probed at this point and therefore it fails e.g. with this message:
>>>>   
>>>> => mtdparts
>>>> Device spi-nand0 not found!
>>>
>>> IIRC, we decided that mtdparts should not call mtd_probe_devices() to
>>> encourage people to stop using it.
>>
>> I see. But I don't quite get how this missing call (and reslting
>> error message) would encourage people to stop using it.
> 
> You're right, this message does not encourage people to stop using
> mtdparts on existing setups (mtdparts should work just fine on any MTD
> devices except SPI NANDs) but it does discourage them from using it on
> spi-nand devices since it returns an error.

IMHO, that's more confusing than discouraging.
  
>>>>
>>>> This patch adds a call to mtd_probe_devices() to mtdparts_init() to
>>>> solve this issue. This also fixes a problem when calling "ubi part"
>>>> as first flash storage related command.
>>>
>>> Hm, this one is unexpected. Miquel, any idea why this happens. Do we
>>> need to enable a specific option if we want mtd_probe_devices() to be
>>> called in the ubi part path?
>>
>> Please note that "ubi part part-foo" does still work. It only
>> prints this error message before attaching the MTD partition.
>> The error is printed because of this call-chain:
>>
>> ubi_part()
>> ->  ubi_detach()
>>       -> mtdparts_init()
>>
>> So again, mtdparts_init() is called without the MTD devices
>> being probed.
> 
> I guess we forgot to remove this mtdparts_init() call from the detach
> path. I think it's no longer needed since we now call
> mtd_probe_devices() in ubi_part(), and mtd_probe_devices() will take
> care of creating MTD partitions based on the mtdparts= and mtdids=
> variables.

A quick test reveals that this removal does not remove the
error message. Instead the command does not work anymore at
all:

=> ubi part nand
Partition nand not found!

Before (and without my patch) its this:

=> ubi part nand
Device spi-nand0 not found!
Error initializing mtdparts!
ubi0: attaching mtd2
ubi0: scanning is finished
ubi0: attached mtd2 (name "nand", size 128 MiB)
...

Thanks,
Stefan