From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hal Rosenstock Subject: Re: [PATCH V2] libibumad: update umad_recv man page. Date: Fri, 06 Jul 2012 15:41:20 -0400 Message-ID: <4FF73F60.1090201@dev.mellanox.co.il> References: <20120703095522.1e89cd25.weiny2@llnl.gov> <4FF72FB0.6020202@dev.mellanox.co.il> <20120706122408.2540ea8dd74f94dcadd3fce1@llnl.gov> <4FF73D63.9010704@dev.mellanox.co.il> <20120706123804.d3d836b998988a2cc5be0ca5@llnl.gov> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20120706123804.d3d836b998988a2cc5be0ca5-i2BcT+NCU+M@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Ira Weiny Cc: "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: linux-rdma@vger.kernel.org On 7/6/2012 3:38 PM, Ira Weiny wrote: > On Fri, 06 Jul 2012 15:32:51 -0400 > Hal Rosenstock wrote: > >> On 7/6/2012 3:24 PM, Ira Weiny wrote: >>> On Fri, 06 Jul 2012 14:34:24 -0400 >>> Hal Rosenstock 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 >>>>> --- >>>>> 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() + > ^^^^^^ > must > > Oh, You mean must here? Yes, if that's the direction you choose (must rather than should). -- Hal > Ira > > >>>>> +.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. >> >> My only point here is that if it's less than 256 + header, then the >> error is returned (and nothing useful can be done). To me, that makes it >> a should rather than a must but just make the two lines consistent. >> Roland does have this as a must in user_mad.txt kernel doc: >> "The buffer passed to read() must be at least one struct ib_user_mad + >> 256 bytes." >> >> -- Hal >> >>> 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" >>>> >>> >>> >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-rdma" in >> the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html