Re: [PATCH V2] libibumad: update umad_recv man page.

Ira Weiny
2012-07-06T19:24:08Z

On Fri, 06 Jul 2012 14:34:24 -0400
Hal Rosenstock <hal-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org> wrote:

> On 7/3/2012 12:55 PM, Ira Weiny wrote:
> >
> > Document the umad_recv length parameter better.
> >
> > Changes since V1:
> > add comments from Hal
> >
> > Signed-off-by: Ira Weiny <weiny2-i2BcT+NCU+M@public.gmane.org>
> > ---
> > man/umad_recv.3 | 18 +++++++++++++++++-
> > 1 files changed, 17 insertions(+), 1 deletions(-)
> >
> > diff --git a/man/umad_recv.3 b/man/umad_recv.3
> > index e1b2985..310d3d2 100644
> > --- a/man/umad_recv.3
> > +++ b/man/umad_recv.3
> > @@ -27,10 +27,26 @@ A negative
> > makes the function block until a packet is received. A
> > .I timeout_ms\fR
> > parameter of zero indicates a non blocking read.
> > +
> > +.B Note
> > +.I length
> > +is a pointer to the length of the
> > +.B data
> > +portion of the umad buffer. This means that
> > +.I umad
> > +should point to a buffer at least umad_size() +
> > +.I *length
> > +bytes long.
> > +
> > +.B Note also
> > +that
> > +.I *length\fR
> > +must be >= 256 bytes.
>
> This seems somewhat redundant to me as just above it says "should point
> to a bugger that's at least umad_size() + *length bytes long.
>
> Also, if this remains, should "must be" be "should be" ?

I _guess_ it _could_ be less than 256. However the specification states:

"C13-3: The data payload (as used in Chapter 9: Transport Layer on page 233) for all MADs shall be exactly 256 bytes."

Furthermore, the kernel checks to ensure that *length is > the first (or only) packet in the MAD transaction. While some Class/Attributes may allow for less "valid" data I'm not sure the kernel distinguishes that. Therefore, I think it is safer to just specify it. Don't you think?

Ira

>
> > +
> > .SH "RETURN VALUE"
> > .B umad_recv()
> > returns non negative receiving agentid on success, and a negative value on error as follows:
> > - -EINVAL invalid port handle or agentid
> > + -EINVAL invalid port handle or agentid or *length is less than the minimum
>
> Rather than just minimum, minimum support length might be clearer.
>
> -- Hal
>
> > -EIO receive operation failed
> > -EWOULDBLOCK non blocking read can't be fulfilled
> > .SH "SEE ALSO"
>

--
Ira Weiny
Member of Technical Staff
Lawrence Livermore National Lab
925-423-8008
weiny2-i2BcT+NCU+M@public.gmane.org