On Thu, Feb 08, 2024 at 07:13:18PM +0100, Erick Archer wrote: > The "struct i915_syncmap" uses a dynamically sized set of trailing > elements. It can use an "u32" array or a "struct i915_syncmap *" > array. > > So, use the preferred way in the kernel declaring flexible arrays [1]. > Because there are two possibilities for the trailing arrays, it is > necessary to declare a union and use the DECLARE_FLEX_ARRAY macro. > > The comment can be removed as the union is now clear enough. > > Also, avoid the open-coded arithmetic in the memory allocator functions > [2] using the "struct_size" macro. > > Moreover, refactor the "__sync_seqno" and "__sync_child" functions due > to now it is possible to use the union members added to the structure. > This way, it is also possible to avoid the open-coded arithmetic in > pointers. > > Link: https://www.kernel.org/doc/html/next/process/deprecated.html#zero-length-and-one-element-arrays [1] > Link: https://www.kernel.org/doc/html/next/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [2] > Signed-off-by: Erick Archer <erick.archer@xxxxxxx> > --- > drivers/gpu/drm/i915/i915_syncmap.c | 19 ++++++++----------- > 1 file changed, 8 insertions(+), 11 deletions(-) > > diff --git a/drivers/gpu/drm/i915/i915_syncmap.c b/drivers/gpu/drm/i915/i915_syncmap.c > index 60404dbb2e9f..df6437c37373 100644 > --- a/drivers/gpu/drm/i915/i915_syncmap.c > +++ b/drivers/gpu/drm/i915/i915_syncmap.c > @@ -75,13 +75,10 @@ struct i915_syncmap { > unsigned int height; > unsigned int bitmap; > struct i915_syncmap *parent; > - /* > - * Following this header is an array of either seqno or child pointers: > - * union { > - * u32 seqno[KSYNCMAP]; > - * struct i915_syncmap *child[KSYNCMAP]; > - * }; > - */ > + union { > + DECLARE_FLEX_ARRAY(u32, seqno); > + DECLARE_FLEX_ARRAY(struct i915_syncmap *, child); > + }; This is a new code pattern for me! Trailing arrays of different element sizes but with a fixed element count. :) I hope when __counted_by is expanded to take expressions we can add a literal. :) Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> -- Kees Cook
