[PATCH 01/41] drm/gem: Add drm_gem_dumb_map_offset()

[Emil Velikov]

Hi Noralf,


On 23 July 2017 at 20:16, Noralf Trønnes <noralf at tronnes.org> wrote:
> Add a common drm_driver.dumb_map_offset function for GEM backed drivers.
>
> Signed-off-by: Noralf Trønnes <noralf at tronnes.org>
> ---
>  drivers/gpu/drm/drm_gem.c | 35 +++++++++++++++++++++++++++++++++++
>  include/drm/drm_gem.h     |  2 ++
>  2 files changed, 37 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> index 5df028a..a8d396b 100644
> --- a/drivers/gpu/drm/drm_gem.c
> +++ b/drivers/gpu/drm/drm_gem.c
> @@ -311,6 +311,41 @@ drm_gem_handle_delete(struct drm_file *filp, u32 handle)
>  EXPORT_SYMBOL(drm_gem_handle_delete);
>
>  /**
> + * drm_gem_dumb_map_offset - return the fake mmap offset for a gem object
> + * @file: drm file-private structure containing the gem object
> + * @dev: corresponding drm_device
> + * @handle: gem object handle
> + * @offset: return location for the fake mmap offset
> + *
> + * This implements the &drm_driver.dumb_map_offset kms driver callback for
> + * drivers which use gem to manage their backing storage.
> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.
> + */
> +int drm_gem_dumb_map_offset(struct drm_file *file, struct drm_device *dev,
> +                           u32 handle, u64 *offset)
> +{
> +       struct drm_gem_object *obj;
> +       int ret;
> +
> +       obj = drm_gem_object_lookup(file, handle);
> +       if (!obj)
> +               return -ENOENT;
> +
> +       ret = drm_gem_create_mmap_offset(obj);
With later patches one goes to reuse this helper instead of
drm_gem_cma_dumb_map_offset().
At the same time, the latter does not have the
drm_gem_create_mmap_offset() call we see here.

Meanwhile some drivers have their own offset function which is
virtually identical to the original drm_gem_cma_dumb_map_offset.
Yet those are left unchanged.

For example in cirrus [1]:
There the only code difference seems to be an "upcast" followed
immediately by a "downcast". Which should effectively be a noop.

That said, I could be loosing my marbles.

HTH
Emil

[1] https://cgit.freedesktop.org/drm/drm-misc/tree/drivers/gpu/drm/cirrus/cirrus_main.c#n292