From 3e737e394329564b70ceff8eb0c5f587904aa396 Mon Sep 17 00:00:00 2001 From: Kieran Bingham Date: Fri, 3 Aug 2018 07:37:21 -0400 Subject: [PATCH] media: vsp1: use kernel __packed for structures The kernel provides a __packed definition to abstract away from the compiler specific attributes tag. Convert all packed structures in VSP1 to use it. The GCC documentation [0] describes this attribute as "the structure or union is placed to minimize the memory required". The Keil compiler documentation at [1] warns that the use of this attribute can cause a performance penalty in the event that the compiler can not deduce the allignment of each field. Careful examination of the object code generated both with and without this attribute shows that these structures are accessed identically and are not affected by any performance penalty. The structures are correctly aligned and padded to match the needs of the hardware already. This patch does not serve to make a decision as to the use of the attribute, but purely to clean up the code to use the kernel defined abstraction as per [2]. [0] https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute [1] http://www.keil.com/support/man/docs/armcc/armcc_chr1359124230195.htm [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/compiler-gcc.h?h=v4.16-rc5#n92 Signed-off-by: Kieran Bingham Signed-off-by: Laurent Pinchart Signed-off-by: Mauro Carvalho Chehab --- drivers/media/platform/vsp1/vsp1_dl.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/media/platform/vsp1/vsp1_dl.c b/drivers/media/platform/vsp1/vsp1_dl.c index 10a24bd..e4aae33 100644 --- a/drivers/media/platform/vsp1/vsp1_dl.c +++ b/drivers/media/platform/vsp1/vsp1_dl.c @@ -25,19 +25,19 @@ struct vsp1_dl_header_list { u32 num_bytes; u32 addr; -} __attribute__((__packed__)); +} __packed; struct vsp1_dl_header { u32 num_lists; struct vsp1_dl_header_list lists[8]; u32 next_header; u32 flags; -} __attribute__((__packed__)); +} __packed; struct vsp1_dl_entry { u32 addr; u32 data; -} __attribute__((__packed__)); +} __packed; /** * struct vsp1_dl_body - Display list body -- 2.7.4