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

[Daniel Wagner]

On 07/31/2016 09:23 AM, Dmitry Torokhov wrote:
> On July 30, 2016 9:58:17 AM PDT, "Luis R. Rodriguez" <mcgrof@xxxxxxxxxx> wrote:
> > On Sat, Jul 30, 2016 at 02:42:41PM +0200, Arend van Spriel wrote:
> > > On 29-07-16 08:13, Daniel Wagner wrote:
> > > > On 07/28/2016 09:01 PM, Bjorn Andersson wrote:
> > > > > On Thu 28 Jul 11:33 PDT 2016, Dmitry Torokhov wrote:

> > > + Luis (again) ;-)

That was not on purpose :) My attempt to keep the Cc list a bit shorter 
was a failure.

> > > > > > Do not quite like it... I'd rather asynchronous request give out
> > > > > > firmware status pointer that could be used later on.
> > >
> > > Excellent. Why not get rid of the callback function as well and have
> > > fw_loading_wait() return result (0 = firmware available, < 0 = fail).
> > > Just to confirm, you are proposing a new API function next to
> > > request_firmware_nowait(), right?
> >
> > If proposing new firmware_class patches please bounce / Cc me, I've
> > recently asked for me to be added to MAINTAINERS so I get these
> > e-mails as I'm working on a new flexible API which would allow us
> > to extend the firmware API without having to care about the old
> > stupid usermode helper at all.

These patches here are a first attempt to clean up a bit of the code 
around the completion API. As Dmitry correctly pointed out, it makes 
more sense to go bit further and make the async loading a bit more 
convenient for the drivers.

> I am not sure why we started calling usermode helper "stupid". We
> only  had to implement direct kernel firmware loading because udev/stsremd
> folks had "interesting" ideas how events should be handled; but having
> userspace to feed us data is not stupid.

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.

> 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.

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)

Step 2 could be something more towards sysdata approach.

cheers,
daniel