nios2-linux kernel porting issue from 3.10 to 4.1

[Altera_Forum]

Hi, 

 I have been using nios2-linux distribution with kernel v3.04 and v3.10 for USB device driver development. Now I want switch from kernel v3.10 to v4.1. In order to do so, I have downloaded nios2-linux source from github and replaced 3.10 source with this newer one. But while building the image, i am facing below described error in entry.s(../arch/nios2/kenrel/entry.s) file:  ../arch/nios2/kernel/entry.s:552: error: non-constant expression in ".if" statement ../arch/nios2/kernel/entry.s:552: error: bad or irreducible absolute expression  Then I commented that statement(line 552) in order to see if there any errors or dependencies with this error. But image compiled successfully with unexpected size of 3.6 MB (because generally it was around 5-6 MB while using v3.10). I ran the image and everything executed fine until below message showed up:  vfs: cannot open root device "(null)" or unknown-block(0,0): error -6 please append a correct "root=" boot option; here are the available partitions: 0100 4096 ram0 (driver?) 0101 4096 ram1 (driver?) 0102 4096 ram2 (driver?) 0103 4096 ram3 (driver?) 0104 4096 ram4 (driver?) 0105 4096 ram5 (driver?) 0106 4096 ram6 (driver?) 0107 4096 ram7 (driver?) 0108 4096 ram8 (driver?) 0109 4096 ram9 (driver?) 010a 4096 ram10 (driver?) 010b 4096 ram11 (driver?) 010c 4096 ram12 (driver?) 010d 4096 ram13 (driver?) 010e 4096 ram14 (driver?) 010f 4096 ram15 (driver?) kernel panic - not syncing: vfs: unable to mount root fs on unknown-block(0,0) ---[ end kernel panic - not syncing: vfs: unable to mount root fs on unknown-block(0,0) random: nonblocking pool is initialized  It looks like, we are not getting root file system properly and kernel gets panicked.  I will appreciate any type of suggestion or help. Thanks in advance.  Regards, Parth Shah