| Message ID | 1456174024-11389-2-git-send-email-sakari.ailus@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Em Mon, 22 Feb 2016 22:47:01 +0200 Sakari Ailus <sakari.ailus@linux.intel.com> escreveu: > From: Sakari Ailus <sakari.ailus@iki.fi> > > The argument structs are used in arrays for G_TOPOLOGY IOCTL. The > arguments themselves do not need to be aligned to a power of two, but > aligning them up to the largest basic type alignment (u64) on common ABIs > is a good thing to do. > > The patch changes the size of the reserved fields to 8 or 9 u32's and > aligns the size of the struct to 8 bytes so we do no longer depend on the > compiler to perform the alignment. I ran some tests with both x86_64 and arch64 running both 32 and 64 bits userspace versions of mc_nextgen_test. Everything is working fine with the current structures. No need for any extra alignment or compat32 bits. So, this patch is not needed. Yet, I agree that it could be useful to do 64 bits alignment, but I guess we're reserving too much space. So, except for media_v2_interface, I would be reserving 5 or 6 u32 space, as it is likely mor than enough for future usage. See below. > > Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com> > --- > include/uapi/linux/media.h | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/include/uapi/linux/media.h b/include/uapi/linux/media.h > index 6aac2f0..1468651 100644 > --- a/include/uapi/linux/media.h > +++ b/include/uapi/linux/media.h > @@ -302,7 +302,7 @@ struct media_v2_entity { > __u32 id; > char name[64]; /* FIXME: move to a property? (RFC says so) */ > __u32 function; /* Main function of the entity */ > - __u16 reserved[12]; > + __u32 reserved[8]; You extended the size here. Any reason? If not I would use, instead: __u32 reserved[6]; > }; > > /* Should match the specific fields at media_intf_devnode */ > @@ -327,7 +327,7 @@ struct media_v2_pad { > __u32 id; > __u32 entity_id; > __u32 flags; > - __u16 reserved[9]; > + __u32 reserved[9]; Again, you're doubling the reserved space here. Any reason? If not, I would use, instead: __u32 reserved[5]; > }; > > struct media_v2_link { > @@ -335,7 +335,7 @@ struct media_v2_link { > __u32 source_id; > __u32 sink_id; > __u32 flags; > - __u32 reserved[5]; > + __u32 reserved[8]; Again, you're doubling the reserved space here. Any reason? If not, I would use, instead: __u32 reserved[6]; > }; > > struct media_v2_topology {
diff --git a/include/uapi/linux/media.h b/include/uapi/linux/media.h index 6aac2f0..1468651 100644 --- a/include/uapi/linux/media.h +++ b/include/uapi/linux/media.h @@ -302,7 +302,7 @@ struct media_v2_entity { __u32 id; char name[64]; /* FIXME: move to a property? (RFC says so) */ __u32 function; /* Main function of the entity */ - __u16 reserved[12]; + __u32 reserved[8]; }; /* Should match the specific fields at media_intf_devnode */ @@ -327,7 +327,7 @@ struct media_v2_pad { __u32 id; __u32 entity_id; __u32 flags; - __u16 reserved[9]; + __u32 reserved[9]; }; struct media_v2_link { @@ -335,7 +335,7 @@ struct media_v2_link { __u32 source_id; __u32 sink_id; __u32 flags; - __u32 reserved[5]; + __u32 reserved[8]; }; struct media_v2_topology {