[SPAM] Sculpt scenario and block devices

[Tomasz Gajewski]

Josef Söntgen <josef.soentgen at ...1...> writes:

> Hello Tomasz,
>
> thanks for the feedback!
>
> * Tomasz Gajewski <tomga at ...300...> [2018-03-04 12:09:56 +0100]:
>> I can see block devices reported in /report/drivers/block_devices but
>> I have two disks so driver_manager is not marking any of my disks as
>> default.
>>
>> Both disks are partitioned and I could give one partition exclusively
>> to Genode to continue playing with it but not whole disk.
>>
>> […]
>>
>> I think there are two possibilities to continue.
>>
>> First is to change Sculpt configuration during preparing image to
>> match my configuration.
>
> I have a similar setup (two disks, both partitioned) and I would
> recommend to choose this option for now as you only need to change the
> fs subinit to match your setup, i.e. point 'part_blk' to the proper
> Block session and 'vfs' to the partition.

Can you share your configuration or is it already available somewhere?
It would be easier to understand and modify working configuration
instead of experimenting with part_blk examples.

>> Second is to change implementation of some component
>> (?driver_manager?0 to be flexible enough to automatically handle all
>> my devices: disks (ahci), partitions on disks (part_blk on ahci
>> devices), usb drives (usb), partitions on usb drives and expose
>> them. Later it should be possible to just select a block device which
>> user would like to user for Genode.
>>
>> […]
>>
>> I think that for each disk device (either ahci or usb) something
>> should start part_blk for it, check if it properly detected
>> partitions and expose them.
>
> I agree, having some kind of probing mechanism in place would be nice
> and is certainly something we want to address in future Sculpt
> iterations. It stands to reason where to put such a probing mechanism,
> though. I am not sure if the drivers subsystem is the proper place.

I didn't want to suggest a place for this functionality but in my
opinion as a new user it is crucial to allow new people to come to
project. Currently this step is hard to overcome. You have to have one
drive and format it whole for Genode or you have to be a Genode expert
to go on further (or ask for an example :-) ).

> Although it would be nice to handle Block sessions transparently for
> the other subsystems, it would increase the complexity of the mostly
> static drivers subsystem (that is, if we ignore USB providing more
> than its Usb session). The current layering of Sculpt subsystems
> considering complexity and dynamic composition is first the drivers,
> than run-time subsystem and at the very top the deploy mechanism…

>> Addtionally there should be a configuration option that could be
>> easily set in some config that would make a specific block device a
>> default one (instead of policy that marks it as default if there is
>> only one device).
>
> … and at the moment, to make things simple, we rely on a somewhat
> static configuration to point the deploy run-time to the depot
> location. Apart from that, however, it is perfectly fine to make all
> decisions in the run-time subsystem and, depending on the use case,
> even above that.

It's a complex topic and it's hard for to write good questions for
this. Sculpt as step of scenario prepares disk for later usage with
Genode. That's why I think about it a little like with an installer
where I can point it to some partition instead of using whole disk. And
this step should not be performed with rebuilding a scenario - it should
be available after running it and done in as easy as possible steps. And
ideally after doing this once it could be later autodetected as Genode
partition and used automatically the second time I start Sculpt.

>From what I know about the project all required elements are available
to make it possible. I'd like to try to make it possible and I'm asking
if you have some ideas about how this could be achieved. driver_manager
is the part that I found that generates dynamically configuration for
drivers depending on detected hardware and that's why I proposed
extending it. Maybe it should be a different component.

> For example, on one hand I want to change the partition table on a
> disk.  That involves getting access to the whole Block device (“stop
> any running 'part_blk'”) to make the change and afterwards re-reading
> the partition table (“start 'part_blk'”). We already have a mechanism
> in place to do just that: changing the configuration of the run-time
> subsystem. On the other hand, if I just want to change the partition
> table on a freshly inserted USB disk, I can do that from within the
> deploy config — no need to change the run-time's configuration.

Ok, so for now I'm thinking only about "system" disk/partition for
Genode.

>> I think you already have some vision how you plan to implement that
>> part of system. Do you plan to extend driver manager implementation?
>
> It really boils down to which services are necessary at which layer
> for the rest of the system to work and what we need to do to use them
> conveniently. If this requires extending the driver manager, we will
> probably do that (although there are other developers that are more
> qualified to comment on that).

I'd like to hear about your, Genode, vision for this. I understand it is
complex. Drivers are needed to have storage. Storage is needed to have
drivers - at least some of them. And generally devices autodetection and
management is complex.


Tomasz Gajewski

PS. I don't know why sourceforge doesn't like my emails today. I've sent
original one 4 times and 3 times it was not accepted with 550 and
congratulations about some points my mail received (number was changing
even though mail was exactly the same) and 4th attempt was marked as
spam. I asked sourceforge about it and I hope they will respond.