Re: [PATCH 27/52] drm: Manage drm_mode_config_init with drmm_

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Daniel,

On Wed, Feb 19, 2020 at 04:47:55PM +0100, Daniel Vetter wrote:
> On Wed, Feb 19, 2020 at 2:50 PM Laurent Pinchart wrote:
> > On Wed, Feb 19, 2020 at 11:20:57AM +0100, Daniel Vetter wrote:
> > > 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.
> > >
> > > Cc: "Noralf Trønnes" <noralf@tronnes.org>
> > > Cc: Sam Ravnborg <sam@ravnborg.org>
> > > Cc: Thomas Zimmermann <tzimmermann@suse.de>
> > > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > > ---
> > >  drivers/gpu/drm/drm_drv.c         | 21 +++++----------------
> > >  drivers/gpu/drm/drm_mode_config.c | 12 +++++++++++-
> > >  include/drm/drm_mode_config.h     |  2 +-
> > >  3 files changed, 17 insertions(+), 18 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> > > index 3cf40864d4a6..428c569aaaf1 100644
> > > --- a/drivers/gpu/drm/drm_drv.c
> > > +++ b/drivers/gpu/drm/drm_drv.c
> > > @@ -267,8 +267,7 @@ 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 +277,8 @@ 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 +303,9 @@ 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 +703,7 @@ 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 +714,6 @@ 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_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
> > > index 08e6eff6a179..957db1edba0c 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 +451,8 @@ void drm_mode_config_init(struct drm_device *dev)
> > >               drm_modeset_acquire_fini(&modeset_ctx);
> > >               dma_resv_fini(&resv);
> > >       }
> > > +
> > > +     return drmm_add_action(dev, drm_mode_config_init_release, NULL);
> >
> > If this fails, shouldn't drm_mode_config_cleanup() be called here ?
> 
> Maybe for ocd reasons, but not for actually cleaning up anything. It's
> just a bunch of empty lists that drm_mode_config_cleanup will walk and
> do nothing about. Not sure I should add that ...

How about the ida init, and the mutex_init() that isn't a no-op when
lock debugging is enabled ?

> > >  }
> > >  EXPORT_SYMBOL(drm_mode_config_init);
> > >
> > > 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);
> > >

-- 
Regards,

Laurent Pinchart
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