On Wed, 2008-09-10 at 19:11 +0300, Boaz Harrosh wrote:
> Dave Kleikamp wrote:
> > @@ -62,7 +60,7 @@ struct timestruc_t {
> > */
> > typedef struct {
> > unsigned len:24;
> > - unsigned off1:8;
> > + u8 off1;
> > u32 off2;
> > } lxd_t;
> >
>
> Why is the difference from below definition. That is the
> use/not of __le24?
Answered elsewhere, but this is host-endian. I plan to kill this
structure soon.
> > @@ -90,8 +88,8 @@ struct lxdlist {
> > * physical xd (pxd)
> > */
> > typedef struct {
> > - unsigned len:24;
> > - unsigned addr1:8;
> > + __le24 len;
>
> Is this stuff on-the-wire?
Written to disk, so basically, yeah.
> Do you need a:
> + __le24 len __packed;
>
> > + u8 addr1;
> > __le32 addr2;
> > } pxd_t;
> and:
> } pxd_t __packed ;
I'm not convinced that this is needed. Does the compiler do any padding
for alignment when it only contains char types (or structs of chars)?
>
> Note that before the :24 bit-field was kept packed but now
> with the use of struct at the __le24 definition it might
> choose to pad them.
Maybe, but I can't get the compiler to add any padding playing around
with variants of these structures. I've tested a simple program on both
x86 and ppc64, but I'm not sure what would happen on, say, arm.
> Chris you might want to change the definitions at linux/types.h
> to:
>
> typedef struct { __u8 b[3]; } __be24, __le24 __packed;
>
> With gcc it will not help with the proceeding fields, and the
> containing struct will need it's own "__packed" declaration
> but it will keep it packed with previous fields.
>
> Just my $0.017
> Boaz
Shaggy
--
David Kleikamp
IBM Linux Technology Center
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