Hi Neerav,
thanks very much for your quick reply!
On 08/09/2012 09:29 PM, Parikh, Neerav wrote:
-----Original Message-----
From: linux-scsi-owner@xxxxxxxxxxxxxxx [mailto:linux-scsi-
owner@xxxxxxxxxxxxxxx] On Behalf Of Steffen Maier
Sent: Thursday, August 09, 2012 9:15 AM
Lately, commit
a9277e7783651d4e0a849f7988340b1c1cf748a4
"[SCSI] scsi_transport_fc: Getting FC Port Speed in sync with FC-GS"
reverted this.
(See also http://marc.info/?l=linux-scsi&m=132892310322550&w=2.)
One thing that I seem to miss is the RPSC ELS have some different definitions
for speed as compared to the FC_PORTSPEED before this commit as well. Does the
zfcp HBA FW do some internal conversion resulting into speed values that
were in sync with the prior FC_PORTSPEED values?
Assuming you refer to the reversed bit order, then this is handled by
the HBA and therefore matches the prior FC_PORTSPEED values.
kernel before a9277e7 FC-GS RPSC ELS Sec.6.2.3.3.8+9
Bit Description
------------------------------------|------------------------------
#define FC_PORTSPEED_UNKNOWN 0 -
#define FC_PORTSPEED_1GBIT 1 15 1 Gb/s capable
#define FC_PORTSPEED_2GBIT 2 14 2 Gb/s capable
#define FC_PORTSPEED_4GBIT 4 13 4 Gb/s capable
#define FC_PORTSPEED_10GBIT 8 12 10 Gb/s capable
#define FC_PORTSPEED_8GBIT 0x10 11 8 Gb/s capable
#define FC_PORTSPEED_16GBIT 0x20 10 16 Gb/s capable
9 20 Gb/s capable
8 32 Gb/s capable
7 40 Gb/s capable
6-2 Reserved
1 Unknown
#define FC_PORTSPEED_NOT_NEGOTIATED
(1 << 15) 0 Speed not established
I don't mind converting zfcp to an explicit finite bit
conversion based on individually defined constants, esp. since all
other
FC LLDDs (qla2xxx, bfa, lpfc, ibmvscsi, fnic, mptfc) seem to do so
already. The only slight drawback I can see is that the code needs to
be touched for new HBA generations supporting new port speeds.
I think, I'm going to bring zfcp in line with the other LLDs and do an
explicit conversion for the following reasons:
Independence of any current kernel port speed semantics.
I have to do service for enterprise distros anyway (even if you revert
your commit upstream) since some seem to have to picked up a9277e7 already.
3) Should we have port speed defines for both RPSC ELS (in
include/fc/fc_els.h?) and FDMI port attributes (in
include/scsi/scsi_transport_fc.h? unless the bit semantic change gets
reverted)?
This way I could reuse the former to convert to the latter within zfcp
and other users can reuse it with regard to RPSC ELS. I would send a
patch if we agree on this.
I guess, there is no other user currently so I might just code it inside
zfcp without definitions in fc_els.h unless someone wants me to.
Also, regardless of the approach you decide on wouldn't zfcp need to make
sure the speed values reported by HBA FW is in sync with the in kernel
values?
Not necessarily, because we don't synchronize the bit semantics between
HBA and kernel, but between HBA and FC-GS RPSC ELS in reversed bit
order. If the kernel would also remain using the semantics of FC-GS RPSC
ELS in reversed bit order, then the HBA values would automatically match
the kernel definitions.
However, that's no longer relevant with an explicit conversion in zfcp.
Regards,
Steffen
Linux on System z Development
IBM Deutschland Research & Development GmbH
Vorsitzende des Aufsichtsrats: Martina Koederitz
Geschäftsführung: Dirk Wittkopp
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