Re: [PATCH v3] regmap: add iopoll-like atomic polling macro

[Sameer Pujar]

On 1/9/2020 7:27 PM, Dmitry Osipenko wrote:
> External email: Use caution opening links or attachments
>
>
> 09.01.2020 10:24, Sameer Pujar ÐÐÑÐÑ:
> > On 1/9/2020 11:30 AM, Dmitry Osipenko wrote:
> > > External email: Use caution opening links or attachments
> > >
> > >
> > > 09.01.2020 08:09, Sameer Pujar ÐÐÑÐÑ:
> > > > This patch adds a macro 'regmap_read_poll_timeout_atomic' that works
> > > > similar to 'readx_poll_timeout_atomic' defined in linux/iopoll.h; This
> > > > is atomic version of already available 'regmap_read_poll_timeout' macro.
> > > >
> > > > It should be noted that above atomic macro cannot be used by all
> > > > regmaps.
> > > > If the regmap is set up for atomic use (flat or no cache and MMIO) then
> > > > only it can use.
> > > >
> > > > Signed-off-by: Sameer Pujar <spujar@xxxxxxxxxx>
> > > > ---
> > > Could you please explain what is the targeted use-case here?
> > I was trying to use regmap_read_poll_timeout() to poll for status change
> > of a register. This resulted in "BUG: scheduling while atomic". The
> > callback function, in which I was trying to use the macro, runs in
> > atomic context. Hence new atomic macro is added. I was checking ALSA
> > playback/capture and trigger() callback had to monitor some register
> > status.
> >
> > In general, the new macro can be used in atomic callbacks where regmap
> > interface is used and polling is required.
> You should send a full patchset because it may turn out that the patch
> which makes use of the new feature isn't correct or maybe the new
> feature isn't really needed.
>
> If there was a previous discussion about the need for this change, then
> you should provide a link to that discussion.
>
> Please note that usually changes without a real use-case in kernel are
> not getting picked up or they are getting removed later on if nobody
> makes use of them, so I assume this is a kind of an RFC patch for now.

OK. I will send this as part of the complete series. Thank you.