Hello Bart, On Fri, Nov 24, 2023 at 10:16:40PM +0100, Bartosz Golaszewski wrote: > On Fri, Nov 24, 2023 at 1:14 PM Thierry Reding <thierry.reding@xxxxxxxxx> wrote: > > On Wed, Nov 22, 2023 at 11:36:19AM +0100, Bartosz Golaszewski wrote: > > > On Wed, Nov 22, 2023 at 10:05 AM Uwe Kleine-König > > > <u.kleine-koenig@xxxxxxxxxxxxxx> wrote: > > > > On Tue, Nov 21, 2023 at 05:11:11PM +0100, Uwe Kleine-König wrote: > > > > > On Tue, Nov 21, 2023 at 03:02:39PM +0100, Bartosz Golaszewski wrote: > > > > > > Eh... I had a talk at LPC where I explained why I really dislike this > > > > > > approach but I guess this ship has sailed now and it's not a subsystem > > > > > > where I have any say anyway. > > > > > > > > > > Is there a record of your talk? I'm open to hear your arguments. > > > > > > > > I found your slides at > > > > https://lpc.events/event/17/contributions/1627/attachments/1258/2725/Linux%20Plumbers%20Conference%202023.pdf > > > > > > > > > > My talk is here: https://www.youtube.com/watch?v=VxaAorwL89c&t=29310s > > > > I've been watching this along with Laurent's talk from last year (and I > > guess I should probably also go through Wolfram's patch from earlier > > this year) and I really like what you presented. It also sounds like > > there was a lot of support across various audience members, so I think > > it'd be good to rally around such a common pattern so we can start to > > improve things on a more wide basis. > > > > Given that this wasn't very long ago, I wouldn't expect that much work > > has happened yet on the resmgr library. However, I think it would fit > > very well both with how PWM works today and with what Uwe has in mind > > for the character device support. > > > > Thierry > > Hi Thierry, > > Thanks for the kind words. No work has been done so far other than > thinking about the possible API. I'm currently in the process of > trying to fix the object life-time and concurrent access in GPIO - > mostly improving the dire locking situation. My goal is to implement > all I spoke about in GPIO first and then try to generalize it to some > other subsystem like what Greg KH suggested. > > I've already got support from Wolfram on that and we of course could > use any help we can get. > > I admit I've been quite busy but I do plan on going through Uwe's > series next week and maybe running tests similar to what I have for > GPIO on it. I'm quite certain (correct me if I'm wrong) that this > series doesn't improve the locking (specifically hot-unplug events > during API calls). I think that my proposal has the advantage of > having the pointer to the implementation in the "wrapper" which can be > easily protected with RCU. Maybe I didn't understand the problem yet, but I think hotplugging isn't a problem for my approach. The hardware accesses in the lowlevel driver (probably) fail then but that's something you cannot prevent. And because pwmchip->lock is held during calls in the lowlevel driver, removal of the driver is delayed accordingly. Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | https://www.pengutronix.de/ |
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