[PATCH] drm: Update drm_device docs about embedding.

[Chris Wilson]

On Thu, Dec 08, 2016 at 11:28:47AM +0100, Daniel Vetter wrote:
> It's supported now! Spotted while reviewing Chris' patch to add a
> release hook.
> 
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> ---
>  drivers/gpu/drm/drm_drv.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index f74b7d06ec01..4ec61ac27477 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -323,9 +323,8 @@ void drm_minor_release(struct drm_minor *minor)
>   * historical baggage. Hence use the reference counting provided by
>   * drm_dev_ref() and drm_dev_unref() only carefully.
>   *
> - * Also note that embedding of &drm_device is currently not (yet) supported (but
> - * it would be easy to add). Drivers can store driver-private data in the
> - * dev_priv field of &drm_device.
> + * It is recommended that drivers embed struct &drm_device into their own device
> + * structure, which is supported through drm_dev_init().
>   */
>  
>  /**
> @@ -462,7 +461,11 @@ static void drm_fs_inode_free(struct inode *inode)
>   * Note that for purely virtual devices @parent can be NULL.
>   *
>   * Drivers that do not want to allocate their own device struct
> - * embedding struct &drm_device can call drm_dev_alloc() instead.
> + * embedding struct &drm_device can call drm_dev_alloc() instead. For drivers
> + * that do embed struct &drm_device it must be placed first in the overall
> + * structure, and the overall structure must be allocated using kmalloc(): The
> + * drm core's release function unconditionally calls kfree() on the @dev pointer
> + * when the final reference is released.

Hmm, the privates are getting pretty big (drm_i915_private fits inside
malloc-32678). We should start considering using drm_free_large() instead
as that more or less work transparently and allows fallback to vmalloc.

As it stands the doc update is correct, so
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre