[RFC 1/3] drm: Add a way to iterate over minors

[Daniel Vetter]

On Tue, Aug 09, 2016 at 07:45:40PM +0200, Noralf Trønnes wrote:
> This adds a way for in-kernel users to iterate over the available
> DRM minors. The implementation is oops safe so the panic code
> can safely use it.
> 
> Signed-off-by: Noralf Trønnes <noralf at tronnes.org>

Why iterate over minors? I'd kinda have expected we'd iterate over devices
instead ... And looking ahead, that seems to be what you actually want.
-Daniel

> ---
>  drivers/gpu/drm/drm_drv.c | 30 ++++++++++++++++++++++++++++++
>  include/drm/drmP.h        | 13 +++++++++++++
>  2 files changed, 43 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index be27ed3..3b14366 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -292,6 +292,36 @@ void drm_minor_release(struct drm_minor *minor)
>  }
>  
>  /**
> + * drm_minor_lookup - Lookup DRM minor
> + * @minor_id: Minor ID of the DRM-minor
> + *
> + * Looks up the given minor-ID and returns the respective DRM-minor object.
> + * No reference is taken on the underlying device.
> + * See drm_minor_for_each() for iterating over all minors.
> + *
> + * Returns:
> + * Pointer to minor-object or NULL.
> + */
> +struct drm_minor *drm_minor_lookup(unsigned int minor_id)
> +{
> +	struct drm_minor *minor;
> +	unsigned long flags;
> +	int locked = 1;
> +
> +	if (oops_in_progress)
> +		locked = spin_trylock_irqsave(&drm_minor_lock, flags);
> +	else
> +		spin_lock_irqsave(&drm_minor_lock, flags);
> +
> +	minor = idr_find(&drm_minors_idr, minor_id);
> +
> +	if (locked)
> +		spin_unlock_irqrestore(&drm_minor_lock, flags);
> +
> +	return minor;
> +}
> +
> +/**
>   * DOC: driver instance overview
>   *
>   * A device instance for a drm driver is represented by struct &drm_device. This
> diff --git a/include/drm/drmP.h b/include/drm/drmP.h
> index d377865..bc7006e 100644
> --- a/include/drm/drmP.h
> +++ b/include/drm/drmP.h
> @@ -974,6 +974,19 @@ void drm_dev_unregister(struct drm_device *dev);
>  
>  struct drm_minor *drm_minor_acquire(unsigned int minor_id);
>  void drm_minor_release(struct drm_minor *minor);
> +struct drm_minor *drm_minor_lookup(unsigned int minor_id);
> +
> +/**
> + * drm_minor_for_each - Iterate over DRM minors
> + * @minor: DRM minor handle
> + * @type: DRM minor type to iterate over
> + * @id: id handle
> + *
> + * Iterate over the registered DRM minors of a given type.
> + */
> +#define drm_minor_for_each(minor, type, id)  \
> +	for ((id) = 0; (id) < 64; (id)++)  \
> +		if (((minor) = drm_minor_lookup((id) + (type) * 64)))
>  
>  /*@}*/
>  
> -- 
> 2.8.2
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch