Op 02-02-16 om 14:23 schreef Gustavo Padovan:
> From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
>
> Making fence_info a pointer enables us to extend the struct in the future
> without breaking the ABI.
>
> v2: use type __u64 for fence_info
> Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
> ---
> drivers/staging/android/sync.c | 2 +-
> drivers/staging/android/uapi/sync.h | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/staging/android/sync.c b/drivers/staging/android/sync.c
> index f7530f0..03b1214 100644
> --- a/drivers/staging/android/sync.c
> +++ b/drivers/staging/android/sync.c
> @@ -525,7 +525,7 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
> if (info->status >= 0)
> info->status = !info->status;
>
> - len = sizeof(struct sync_file_info);
> + len = sizeof(struct sync_file_info) - sizeof(__u64);
>
> for (i = 0; i < sync_file->num_fences; ++i) {
> struct fence *fence = sync_file->cbs[i].fence;
> diff --git a/drivers/staging/android/uapi/sync.h b/drivers/staging/android/uapi/sync.h
> index ed281fc..8e2ed32 100644
> --- a/drivers/staging/android/uapi/sync.h
> +++ b/drivers/staging/android/uapi/sync.h
> @@ -54,7 +54,7 @@ struct sync_file_info {
> char name[32];
> __s32 status;
>
> - __u8 fence_info[0];
> + __u64 fence_info;
>
With the information from the commit I would expect fence_info would be a true pointer.
so if (sync_file_info->num_fences == 0) not copying fence_info, but set all members including this one.
else for_all_fences() copy_to_user(fence_info struct)
Otherwise you still can't extend the struct without breaking the abi.
~Maarten
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