How to check for free slots in HBA in solaris 10 .

prtconf

which system (hardware do you have)? that will tell you how many resources your HW has, and based on used slots ...

devfsadm ...

solaris 10 is the OS, ....

prtconf will enumerate a great deal of data, but it will not necessarily tell what ports are empty on all HBAs.  That is because some HBAs effectively put ports in parallel and there is no electrical difference between the two. You can generally find out by simply looking at the board and seeing whether or not each port has a controller chip associated with it.  (But you have to cross reference the part number markings on the chip to see the internal block design).  

looking at the output, you have a qlogic FC controller.  Do you have the /etc/hba.conf file installed with the older SNIA smhba-api program?  It used to be a separate optional download that one could use which would give you the ability to do full port enumeration.

David,

I think the person is looking on whether there are any available slots on the MB/System for additional HBA's rather than available ports (not-used) on installed HBA's.

The enumeration of available ports on an HBA is illustrated in the question through the use of the HBA specific tool, fcinfo, luxadmin, ...