Re: [PATCH 01/18] drm: Introduce drm_mm_create_block()

Ben Widawsky
2012-10-26T21:47:26Z

On Fri, 19 Oct 2012 18:03:07 +0100
Chris Wilson <chris@chris-wilson.co.uk> wrote:

> To be used later by i915 to preallocate exact blocks of space from the
> range manager.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Dave Airlie <airlied@redhat.com>
> Cc: dri-devel@lists.freedestkop.org

With bikesheds below addressed or not:
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
> ---
> drivers/gpu/drm/drm_mm.c | 49
> ++++++++++++++++++++++++++++++++++++++++++++++
> include/drm/drm_mm.h | 4 ++++ 2 files changed, 53 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
> index 9bb82f7..5db8c20 100644
> --- a/drivers/gpu/drm/drm_mm.c
> +++ b/drivers/gpu/drm/drm_mm.c
> @@ -161,6 +161,55 @@ static void drm_mm_insert_helper(struct
> drm_mm_node *hole_node, }
> }
>
> +struct drm_mm_node *drm_mm_create_block(struct drm_mm *mm,
> + unsigned long start,
> + unsigned long size,
> + bool atomic)
> +{

<bikeshed>
You could add a best_fit field like some of the other interfaces which
will try to find a start == hole_start and end == hole_end. I'd guess
this interface won't be called enough to worry about fragmentation too
much though.
</bikeshed>

> + struct drm_mm_node *hole, *node;
> + unsigned long end = start + size;
> +
> + list_for_each_entry(hole, &mm->hole_stack, hole_stack) {
> + unsigned long hole_start;
> + unsigned long hole_end;
> +
> + BUG_ON(!hole->hole_follows);

<bikeshed>
This isn't bad, but I don't think sticking the bug here is all that
helpful in finding where the bug occured, since it wasn't here. WARN is
perhaps more useful, but equally unhelpful IMO.
</bikeshed>

> + hole_start = drm_mm_hole_node_start(hole);
> + hole_end = drm_mm_hole_node_end(hole);
> +
> + if (hole_start > start || hole_end < end)
> + continue;
> +
> + node = drm_mm_kmalloc(mm, atomic);
> + if (unlikely(node == NULL))
> + return NULL;
> +
> + node->start = start;
> + node->size = size;
> + node->mm = mm;
> + node->allocated = 1;
> +
> + INIT_LIST_HEAD(&node->hole_stack);
> + list_add(&node->node_list, &hole->node_list);
> +
> + if (start == hole_start) {
> + hole->hole_follows = 0;
> + list_del_init(&hole->hole_stack);
> + }
> +
> + node->hole_follows = 0;
> + if (end != hole_end) {
> + list_add(&node->hole_stack, &mm->hole_stack);
> + node->hole_follows = 1;
> + }
> +
> + return node;
> + }
> +
> + return NULL;
> +}
> +EXPORT_SYMBOL(drm_mm_create_block);
> +
> struct drm_mm_node *drm_mm_get_block_generic(struct drm_mm_node
> *hole_node, unsigned long size,
> unsigned alignment,
> diff --git a/include/drm/drm_mm.h b/include/drm/drm_mm.h
> index 06d7f79..4020f96 100644
> --- a/include/drm/drm_mm.h
> +++ b/include/drm/drm_mm.h
> @@ -102,6 +102,10 @@ static inline bool drm_mm_initialized(struct
> drm_mm *mm) /*
> * Basic range manager support (drm_mm.c)
> */
> +extern struct drm_mm_node *drm_mm_create_block(struct drm_mm *mm,
> + unsigned long start,
> + unsigned long size,
> + bool atomic);
> extern struct drm_mm_node *drm_mm_get_block_generic(struct
> drm_mm_node *node, unsigned long size,
> unsigned
> alignment,

--
Ben Widawsky, Intel Open Source Technology Center