I am looking for a scsi command that I can use to get device max link capability.
Can I use scsi MODE SENSE (page 19) to read the phy descriptors and get the link speed? But how is it different than max link speed and negotiated linkspeed?
According to SPL-4, you many use SMP DISCOVER function or SCSI MODE SENSE page 19h Protocol Specific Port, subpage 01h Phy Control And Discover.
For link speed, you should use NEGOTIATED LOGICAL LINK RATE. The max link speed are HARDWARE MAXIMUM PHYSICAL LINK RATE (physical limitation) and PROGRAMMED MAXIMUM PHYSICAL LINK RATE (configured by PHY CONTROL function)
This is the example of using SMP DISCOVER way:
[fge@el7 ~]$ sudo smp_discover /dev/bsg/expander-0\:0
phy 0:T:attached:[500015535990a300:00 t(SATA)] 3 Gbps
phy 1:T:attached:[500015535990a301:00 t(SATA)] 3 Gbps
phy 2:T:attached:[500015535990a302:00 t(SATA)] 1.5 Gbps
phy 3:T:attached:[500015535990a303:00 t(SATA)] 3 Gbps
phy 4:T:attached:[500015535990a304:00 t(SATA)] 3 Gbps
phy 5:T:attached:[500015535990a305:00 t(SATA)] 3 Gbps
phy 6:T:attached:[500015535990a306:00 t(SATA)] 3 Gbps
phy 7:T:attached:[500015535990a307:00 t(SATA)] 3 Gbps
phy 8:T:attached:[500015535990a308:00 t(SATA)] 3 Gbps
phy 9:T:attached:[500015535990a309:00 t(SATA)] 3 Gbps
phy 10:T:attached:[500015535990a30a:00 t(SATA)] 3 Gbps
phy 11:T:attached:[500015535990a30b:00 t(SATA)] 3 Gbps
phy 12:T:attached:[500015535990a30c:00 t(SATA)] 3 Gbps
phy 13:T:attached:[500015535990a30d:00 t(SATA)] 3 Gbps
phy 14:T:attached:[50014ee5aaab876f:01 t(SSP)] 3 Gbps
phy 15:T:attached:[500015535990a30f:00 t(SATA)] 3 Gbps
phy 16:S:attached:[5d4ae520995f8200:03 i(SSP+STP+SMP)] 3 Gbps
phy 20:T:attached:[500015535956633f:16 exp i(SMP) t(SMP)] 3 Gbps
phy 21:T:attached:[500015535956633f:17 exp i(SMP) t(SMP)] 3 Gbps
phy 22:T:attached:[500015535956633f:18 exp i(SMP) t(SMP)] 3 Gbps
phy 23:T:attached:[500015535956633f:19 exp i(SMP) t(SMP)] 3 Gbps
phy 24:D:attached:[500015535990a33e:24 V i(SSP) t(SSP)] 3 Gbps