Re: [PATCH 50/51] drm/udl: drop drm_driver.release hook

From: Daniel Vetter <daniel.vetter@ffwll.ch>
To: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Sean Paul <sean@poorly.run>,
	Intel Graphics Development <intel-gfx@lists.freedesktop.org>,
	Emil Velikov <emil.l.velikov@gmail.com>,
	Marco Felsch <m.felsch@pengutronix.de>,
	DRI Development <dri-devel@lists.freedesktop.org>,
	Gerd Hoffmann <kraxel@redhat.com>,
	Daniel Vetter <daniel.vetter@intel.com>,
	Alex Deucher <alexander.deucher@amd.com>,
	Dave Airlie <airlied@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Sam Ravnborg <sam@ravnborg.org>
Subject: Re: [PATCH 50/51] drm/udl: drop drm_driver.release hook
Date: Mon, 2 Mar 2020 10:01:01 +0100	[thread overview]
Message-ID: <CAKMK7uGruuj-q2c+4LfJMM_weCOkkOs7R3QxnQTYfdt4SahBEQ@mail.gmail.com> (raw)
In-Reply-To: <e9fa1b03-e4b7-d65b-8fb8-fe15c20fddc9@suse.de>

On Mon, Mar 2, 2020 at 9:14 AM Thomas Zimmermann <tzimmermann@suse.de> wrote:
>
> Hi Daniel
>
> Am 28.02.20 um 18:43 schrieb Daniel Vetter:
> > On Fri, Feb 28, 2020 at 12:46 PM Thomas Zimmermann <tzimmermann@suse.de> wrote:
> >>
> >> Hi
> >>
> >> Am 28.02.20 um 09:40 schrieb Daniel Vetter:
> >>> On Fri, Feb 28, 2020 at 8:44 AM Thomas Zimmermann <tzimmermann@suse.de> wrote:
> >>>>
> >>>> Hi Daniel
> >>>>
> >>>> Am 27.02.20 um 19:15 schrieb Daniel Vetter:
> >>>>> There's only two functions called from that:
> >>>>> drm_kms_helper_poll_fini() and udl_free_urb_list(). Both of these are
> >>>>> also called from the ubs_driver->disconnect hook, so entirely
> >>>>> pointless to do the same again in the ->release hook.
> >>>>
> >>>> The disconnect hook calls drm_kms_helper_poll_disable() instead if
> >>>> _fini(). They are the same, except that _disable() does not clear
> >>>> dev->mode_config.poll_enabled to false. Is this OK?
> >>>
> >>> oops, I overlooked that. But yeah for driver shutdown it's the same
> >>> really, we're not going to re-enable. _disable is meant for suspend so
> >>> youc an re-enable again on resume.
> >>>
> >>> I'll augment the commit message on the next round to clarify that.
> >>
> >> Well, we have a managed API. It could support
> >> drmm_kms_helper_poll_init(). :)
> >
> > You're ahead of the game here, but yes that's the plan. And a lot
> > more. Ideally I really want to get rid of both bus_driver->remove and
> > drm_driver->release callbacks for all drivers.
> >
> > Also, for polling you actually want devm_kms_poll_init, since polling
> > should be stopped at unplug/remove time. Not at drm_driver release
> > time :-)
>
> Quite honestly, if you're not adding devm_kms_poll_init() now, why even
> bother removing the _fini() call from release()? It hasn't been a
> problem so far and it won't become one. Doing a half-baked change now
> results in a potential WTF moment for other developers.
>
> Rather clean up release() when you add the managed devm_kms_poll_init()
> and have a nice, clear patch.

So the thing is, you need to stop your poll worker in ->unplug, not
->release. That's the part I'm fixing here (plus stopping it twice is
overkill). I'm not seeing any connection to making the ->unplug part
here automatic, that was just a future idea. But this patch series
here is all about ->release stuff. I guess I can do a respin and
change the one in ->unplug from _disable to _fini, which would be
clearer.

But not doing this patch here just because we want to clean things up
even more doesn't make sense to me.
-Daniel

> Best regards
> Thomas
>
>
> > -Daniel
> >
> >>
> >> Best regards
> >> Thomas
> >>
> >>> -Daniel
> >>>
> >>>
> >>>> Best regards
> >>>> Thomas
> >>>>
> >>>>>
> >>>>> Furthermore by the time we clean up the drm_driver we really shouldn't
> >>>>> be touching hardware anymore, so stopping the poll worker and freeing
> >>>>> the urb allocations in ->disconnect is the right thing to do.
> >>>>>
> >>>>> Now disconnect still cleans things up before unregistering the driver,
> >>>>> but that's a different issue.
> >>>>>
> >>>>> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> >>>>> Cc: Dave Airlie <airlied@redhat.com>
> >>>>> Cc: Sean Paul <sean@poorly.run>
> >>>>> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> >>>>> Cc: Thomas Zimmermann <tzimmermann@suse.de>
> >>>>> Cc: Emil Velikov <emil.l.velikov@gmail.com>
> >>>>> Cc: Gerd Hoffmann <kraxel@redhat.com>
> >>>>> Cc: "Noralf Trønnes" <noralf@tronnes.org>
> >>>>> Cc: Sam Ravnborg <sam@ravnborg.org>
> >>>>> Cc: Thomas Gleixner <tglx@linutronix.de>
> >>>>> Cc: Alex Deucher <alexander.deucher@amd.com>
> >>>>> ---
> >>>>>  drivers/gpu/drm/udl/udl_drv.c  |  6 ------
> >>>>>  drivers/gpu/drm/udl/udl_drv.h  |  1 -
> >>>>>  drivers/gpu/drm/udl/udl_main.c | 10 ----------
> >>>>>  3 files changed, 17 deletions(-)
> >>>>>
> >>>>> diff --git a/drivers/gpu/drm/udl/udl_drv.c b/drivers/gpu/drm/udl/udl_drv.c
> >>>>> index b447fb053e78..7f140898df3e 100644
> >>>>> --- a/drivers/gpu/drm/udl/udl_drv.c
> >>>>> +++ b/drivers/gpu/drm/udl/udl_drv.c
> >>>>> @@ -34,14 +34,8 @@ static int udl_usb_resume(struct usb_interface *interface)
> >>>>>
> >>>>>  DEFINE_DRM_GEM_FOPS(udl_driver_fops);
> >>>>>
> >>>>> -static void udl_driver_release(struct drm_device *dev)
> >>>>> -{
> >>>>> -     udl_fini(dev);
> >>>>> -}
> >>>>> -
> >>>>>  static struct drm_driver driver = {
> >>>>>       .driver_features = DRIVER_ATOMIC | DRIVER_GEM | DRIVER_MODESET,
> >>>>> -     .release = udl_driver_release,
> >>>>>
> >>>>>       /* gem hooks */
> >>>>>       .gem_create_object = udl_driver_gem_create_object,
> >>>>> diff --git a/drivers/gpu/drm/udl/udl_drv.h b/drivers/gpu/drm/udl/udl_drv.h
> >>>>> index 1de7eb1b6aac..2642f94a63fc 100644
> >>>>> --- a/drivers/gpu/drm/udl/udl_drv.h
> >>>>> +++ b/drivers/gpu/drm/udl/udl_drv.h
> >>>>> @@ -76,7 +76,6 @@ int udl_submit_urb(struct drm_device *dev, struct urb *urb, size_t len);
> >>>>>  void udl_urb_completion(struct urb *urb);
> >>>>>
> >>>>>  int udl_init(struct udl_device *udl);
> >>>>> -void udl_fini(struct drm_device *dev);
> >>>>>
> >>>>>  int udl_render_hline(struct drm_device *dev, int log_bpp, struct urb **urb_ptr,
> >>>>>                    const char *front, char **urb_buf_ptr,
> >>>>> diff --git a/drivers/gpu/drm/udl/udl_main.c b/drivers/gpu/drm/udl/udl_main.c
> >>>>> index 538718919916..f5d27f2a5654 100644
> >>>>> --- a/drivers/gpu/drm/udl/udl_main.c
> >>>>> +++ b/drivers/gpu/drm/udl/udl_main.c
> >>>>> @@ -351,13 +351,3 @@ int udl_drop_usb(struct drm_device *dev)
> >>>>>       udl_free_urb_list(dev);
> >>>>>       return 0;
> >>>>>  }
> >>>>> -
> >>>>> -void udl_fini(struct drm_device *dev)
> >>>>> -{
> >>>>> -     struct udl_device *udl = to_udl(dev);
> >>>>> -
> >>>>> -     drm_kms_helper_poll_fini(dev);
> >>>>> -
> >>>>> -     if (udl->urbs.count)
> >>>>> -             udl_free_urb_list(dev);
> >>>>> -}
> >>>>>
> >>>>
> >>>> --
> >>>> Thomas Zimmermann
> >>>> Graphics Driver Developer
> >>>> SUSE Software Solutions Germany GmbH
> >>>> Maxfeldstr. 5, 90409 Nürnberg, Germany
> >>>> (HRB 36809, AG Nürnberg)
> >>>> Geschäftsführer: Felix Imendörffer
> >>>>
> >>>
> >>>
> >>
> >> --
> >> Thomas Zimmermann
> >> Graphics Driver Developer
> >> SUSE Software Solutions Germany GmbH
> >> Maxfeldstr. 5, 90409 Nürnberg, Germany
> >> (HRB 36809, AG Nürnberg)
> >> Geschäftsführer: Felix Imendörffer
> >>
> >
> >
>
> --
> Thomas Zimmermann
> Graphics Driver Developer
> SUSE Software Solutions Germany GmbH
> Maxfeldstr. 5, 90409 Nürnberg, Germany
> (HRB 36809, AG Nürnberg)
> Geschäftsführer: Felix Imendörffer
>


-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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