Re: [RFC v0 7/8] Input: ims-pcu: use firmware_stat instead of completion

[Daniel Wagner]

Hi Luis,

> > I was ignorant on all the nasty details around the firmware loading.
> > If I parse Luis' patches correctly they introduce an API which calls
> > kernel_read_file_from_path() asynchronously:
> >
> > sysdata_file_request_async(..., &cookie)
> >   *coookie = async_schedule_domain(request_sysdata_file_work_func(), ..)
> >
> >   request_sysdata_file_work_fun()
> >     _sysdata_file_request()
> >       fw_get_filesystem_firmware()
> > 	kernel_read_file_from_path()
> >
> > sysdata_synchronize_request(&cookie);
> >
> > Doesn't look like what your asking for.
>
> No, but its also a generic kernel read issue as I noted in my last
> reply.

Okay, got it.

> > > If we want to overhaul firmware loading support we need to figure
> > > out  how to support case when a driver want to [asynchronously] request
> > > firmware/config/blob and the rest of the system is not ready. Even if we
> > > want kernel to do read/load the data we need userspace to tell kernel
> > > when firmware partition is available, until then the kernel should not
> > > fail the request.
> >
> > I gather from Luis' blog post and comments that he is on the quest
> > on removing userspace support completely.
>
> No, I explained in my last proposed documentation patch series that we cannot
> get rid of the usermode helper.

I stand corrected.

> Its not well understood why so I explained and documented why.

Obviously, I got lost somewhere there :)

> Best we can do is compartamentalize its uses.

Sounds like a plan.

> The sysdata API's main goal rather is to provide a flexible API first,
> compartamentalizing the usermode helper was secondary. But now it seems
> I may just also add devm support too to help simplify code further.

I missed the point that you plan to add usermode helper support to the 
sysdata API.

> What Dmitry notes is an existential issue with kernel_read_file_from_path()
> and we need a common solution for it.

Understood. I guess best thing to keep that discussion in the other 
subthread.

> > Maybe this attempt here could be a step before. Step 1 would be
> > changing request_firmware_nowait() to request_firmware_async so
> > drivers don't have to come up with their own sync primitives, e.g.
> >
> >   cookie = request_firmware_async()
> >   fw_load_wait(cookie)
>
> That's one of the features already part of async mechanism of the sysdata API :)

Yes, I realized that too :)

cheers,
daniel

Thanks for the feedback.