Union v4l2_event::u is aligned to 8 bytes on arm32. On arm64 v4l2_event32::u
is aligned to 4 bytes. As a result structures v4l2_event and v4l2_event32 have
different sizes and VIDOC_DQEVENT ioctl does not work from arm32 apps running
on arm64 kernel. The patch fixes it.
Signed-off-by: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
---
Hi Hans,
It seems there is problem with VIDIOC_DQEVENT called from arm32 apps on arm64
kernel. After tracking down the issue it seems v4l2_event32 on arm64 have
different field alignment/size than v4l2_event on arm32. The patch fixes it.
But i guess it can break ABI on other architectures. Simple tests shows:
i386:
sizeof(struct v4l2_event)=0x78
offsetof(struct v4l2_event::u)=0x4
amd64:
sizeof(struct v4l2_event)=0x88
offsetof(struct v4l2_event::u)=0x8
arm:
sizeof(struct v4l2_event)=0x80
offsetof(struct v4l2_event::u)=0x8
arm64:
sizeof(struct v4l2_event)=0x88
offsetof(struct v4l2_event::u)=0x8
Any advices how to fix it in arch compatible way?
Regards
Andrzej
---
drivers/media/v4l2-core/v4l2-compat-ioctl32.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
index af63543..a4a1856 100644
--- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
+++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
@@ -739,7 +739,7 @@ struct v4l2_event32 {
__u32 type;
union {
__u8 data[64];
- } u;
+ } u __attribute__((aligned(8)));
__u32 pending;
__u32 sequence;
struct compat_timespec timestamp;
--
1.9.1
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