Re: [PATCH 26/51] drm: Manage drm_mode_config_init with drmm_

[Daniel Vetter <daniel.vetter@ffwll.ch>]

On Fri, Feb 28, 2020 at 8:30 AM Thomas Zimmermann <tzimmermann@suse.de> wrote:
>
> Hi Daniel
>
> Am 27.02.20 um 19:14 schrieb Daniel Vetter:
> > drm_mode_config_cleanup is idempotent, so no harm in calling this
> > twice. This allows us to gradually switch drivers over by removing
> > explicit drm_mode_config_cleanup calls.
> >
> > With this step it's not also possible that (at least for simple
> > drivers) automatic resource cleanup can be done correctly without a
> > drm_driver->release hook. Therefore allow this now in
> > devm_drm_dev_init().
> >
> > Also with drmm_ explicit drm_driver->release hooks are kinda not the
> > best option, so deprecate that hook to discourage future users.
> >
> > v2: Fixup the example in the kerneldoc too.
> >
> > v3:
> > - For paranoia, double check that minor->dev == dev in the release
> >   hook, because I botched the pointer math in the drmm library.
> > - Call drm_mode_config_cleanup when drmm_add_action fails, we'd be
> >   missing some mutex_destroy and ida_cleanup otherwise (Laurent)
> >
> > v4: Add a drmm_add_action_or_reset (like devm_ has) to encapsulate this
> > pattern (Noralf).
> >
> > v5: Fix oversight in the new add_action_or_reset macro (Noralf)
> >
> > Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > Cc: "Noralf Trønnes" <noralf@tronnes.org>
> > Cc: Sam Ravnborg <sam@ravnborg.org>
> > Cc: Thomas Zimmermann <tzimmermann@suse.de>
> > Acked-by: Noralf Trønnes <noralf@tronnes.org>
> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > ---
> >  drivers/gpu/drm/drm_drv.c         | 23 +++++++----------------
> >  drivers/gpu/drm/drm_managed.c     | 14 ++++++++++++++
> >  drivers/gpu/drm/drm_mode_config.c | 13 ++++++++++++-
> >  include/drm/drm_managed.h         |  7 +++++++
> >  include/drm/drm_mode_config.h     |  2 +-
> >  5 files changed, 41 insertions(+), 18 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> > index 3cf40864d4a6..bb326b9bcde0 100644
> > --- a/drivers/gpu/drm/drm_drv.c
> > +++ b/drivers/gpu/drm/drm_drv.c
> > @@ -98,6 +98,8 @@ static void drm_minor_alloc_release(struct drm_device *dev, void *data)
> >       struct drm_minor *minor = data;
> >       unsigned long flags;
> >
> > +     WARN_ON(dev != minor->dev);
> > +
> >       put_device(minor->kdev);
> >
> >       spin_lock_irqsave(&drm_minor_lock, flags);
> > @@ -267,8 +269,7 @@ void drm_minor_release(struct drm_minor *minor)
> >   *
> >   * The following example shows a typical structure of a DRM display driver.
> >   * The example focus on the probe() function and the other functions that is
> > - * almost always present and serves as a demonstration of devm_drm_dev_init()
> > - * usage with its accompanying drm_driver->release callback.
> > + * almost always present and serves as a demonstration of devm_drm_dev_init().
> >   *
> >   * .. code-block:: c
> >   *
> > @@ -278,16 +279,8 @@ void drm_minor_release(struct drm_minor *minor)
> >   *           struct clk *pclk;
> >   *   };
> >   *
> > - *   static void driver_drm_release(struct drm_device *drm)
> > - *   {
> > - *           struct driver_device *priv = container_of(...);
> > - *
> > - *           drm_mode_config_cleanup(drm);
> > - *   }
> > - *
> >   *   static struct drm_driver driver_drm_driver = {
> >   *           [...]
> > - *           .release = driver_drm_release,
> >   *   };
> >   *
> >   *   static int driver_probe(struct platform_device *pdev)
> > @@ -312,7 +305,9 @@ void drm_minor_release(struct drm_minor *minor)
> >   *           }
> >   *           drmm_add_final_kfree(drm, priv);
> >   *
> > - *           drm_mode_config_init(drm);
> > + *           ret = drm_mode_config_init(drm);
> > + *           if (ret)
> > + *                   return ret;
> >   *
> >   *           priv->userspace_facing = drmm_kzalloc(..., GFP_KERNEL);
> >   *           if (!priv->userspace_facing)
> > @@ -710,8 +705,7 @@ static void devm_drm_dev_init_release(void *data)
> >   * @driver: DRM driver
> >   *
> >   * Managed drm_dev_init(). The DRM device initialized with this function is
> > - * automatically put on driver detach using drm_dev_put(). You must supply a
> > - * &drm_driver.release callback to control the finalization explicitly.
> > + * automatically put on driver detach using drm_dev_put().
> >   *
> >   * RETURNS:
> >   * 0 on success, or error code on failure.
> > @@ -722,9 +716,6 @@ int devm_drm_dev_init(struct device *parent,
> >  {
> >       int ret;
> >
> > -     if (WARN_ON(!driver->release))
> > -             return -EINVAL;
> > -
> >       ret = drm_dev_init(dev, driver, parent);
> >       if (ret)
> >               return ret;
> > diff --git a/drivers/gpu/drm/drm_managed.c b/drivers/gpu/drm/drm_managed.c
> > index 626656369f0b..6376be01bbc8 100644
> > --- a/drivers/gpu/drm/drm_managed.c
> > +++ b/drivers/gpu/drm/drm_managed.c
> > @@ -134,6 +134,20 @@ int __drmm_add_action(struct drm_device *dev,
> >  }
> >  EXPORT_SYMBOL(__drmm_add_action);
> >
> > +int __drmm_add_action_or_reset(struct drm_device *dev,
> > +                            drmres_release_t action,
> > +                            void *data, const char *name)
> > +{
> > +     int ret;
> > +
> > +     ret = __drmm_add_action(dev, action, data, name);
> > +     if (ret)
> > +             action(dev, data);
> > +
> > +     return ret;
> > +}
> > +EXPORT_SYMBOL(__drmm_add_action_or_reset);
> > +
> >  void drmm_remove_action(struct drm_device *dev,
> >                       drmres_release_t action,
> >                       void *data)
> > diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
> > index 08e6eff6a179..6f7005bc597f 100644
> > --- a/drivers/gpu/drm/drm_mode_config.c
> > +++ b/drivers/gpu/drm/drm_mode_config.c
> > @@ -25,6 +25,7 @@
> >  #include <drm/drm_drv.h>
> >  #include <drm/drm_encoder.h>
> >  #include <drm/drm_file.h>
> > +#include <drm/drm_managed.h>
> >  #include <drm/drm_mode_config.h>
> >  #include <drm/drm_print.h>
> >  #include <linux/dma-resv.h>
> > @@ -373,6 +374,11 @@ static int drm_mode_create_standard_properties(struct drm_device *dev)
> >       return 0;
> >  }
> >
> > +static void drm_mode_config_init_release(struct drm_device *dev, void *ptr)
> > +{
> > +     drm_mode_config_cleanup(dev);
> > +}
> > +
> >  /**
> >   * drm_mode_config_init - initialize DRM mode_configuration structure
> >   * @dev: DRM device
> > @@ -384,8 +390,10 @@ static int drm_mode_create_standard_properties(struct drm_device *dev)
> >   * problem, since this should happen single threaded at init time. It is the
> >   * driver's problem to ensure this guarantee.
> >   *
> > + * Cleanup is automatically handled through registering drm_mode_config_cleanup
> > + * with drmm_add_action().
> >   */
> > -void drm_mode_config_init(struct drm_device *dev)
> > +int drm_mode_config_init(struct drm_device *dev)
> >  {
> >       mutex_init(&dev->mode_config.mutex);
> >       drm_modeset_lock_init(&dev->mode_config.connection_mutex);
> > @@ -443,6 +451,9 @@ void drm_mode_config_init(struct drm_device *dev)
> >               drm_modeset_acquire_fini(&modeset_ctx);
> >               dma_resv_fini(&resv);
> >       }
> > +
> > +     return drmm_add_action_or_reset(dev, drm_mode_config_init_release,
> > +                                     NULL);
> >  }
> >  EXPORT_SYMBOL(drm_mode_config_init);
>
> It might be a bit late in the review cycle, but could this function be
> renamed to drmm_mode_config_init() to reflect the garbage-collected
> implementation?

I think that makes sense, at least as a wrapper with a __must_check
annotation (and keeping the old one). I tried to avoid the rename
because it'd be a flag day patch.

If you think this would be a great improvement then I can do that -
I'm positive enough to bother with the rebase to touch up all the
driver patches, but only if there's someone else who's enthusiastic
about it :-)
-Daniel

> Best regards
> Thomas
>
> >
> > diff --git a/include/drm/drm_managed.h b/include/drm/drm_managed.h
> > index 2b1ba2ad5582..1e6291407586 100644
> > --- a/include/drm/drm_managed.h
> > +++ b/include/drm/drm_managed.h
> > @@ -18,6 +18,13 @@ int __must_check __drmm_add_action(struct drm_device *dev,
> >                                  drmres_release_t action,
> >                                  void *data, const char *name);
> >
> > +#define drmm_add_action_or_reset(dev, action, data) \
> > +     __drmm_add_action_or_reset(dev, action, data, #action)
> > +
> > +int __must_check __drmm_add_action_or_reset(struct drm_device *dev,
> > +                                         drmres_release_t action,
> > +                                         void *data, const char *name);
> > +
> >  void drmm_remove_action(struct drm_device *dev,
> >                       drmres_release_t action,
> >                       void *data);
> > diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> > index 3bcbe30339f0..160a3e4b51c3 100644
> > --- a/include/drm/drm_mode_config.h
> > +++ b/include/drm/drm_mode_config.h
> > @@ -929,7 +929,7 @@ struct drm_mode_config {
> >       const struct drm_mode_config_helper_funcs *helper_private;
> >  };
> >
> > -void drm_mode_config_init(struct drm_device *dev);
> > +int drm_mode_config_init(struct drm_device *dev);
> >  void drm_mode_config_reset(struct drm_device *dev);
> >  void drm_mode_config_cleanup(struct drm_device *dev);
> >
> >
>
> --
> 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
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel