# HG changeset patch
# User boisy
# Date 1141412514 0
# Node ID 31ca1a8e9a3a3e699d8006f99ef25e9d66ca8b66
# Parent  82198f9cd00442e6191c30c2539c6b48c4b2ac50
Added comments

diff -r 82198f9cd004 -r 31ca1a8e9a3a level1/modules/kernel/krn.asm
--- a/level1/modules/kernel/krn.asm	Fri Mar 03 18:09:29 2006 +0000
+++ b/level1/modules/kernel/krn.asm	Fri Mar 03 19:01:54 2006 +0000
@@ -391,30 +391,82 @@
 L0212    leay  >L0255,pcr
          bra   URtoSs
 
-* X = proc desc
-FAProc   ldx   R$X,u
-L021A    pshs  u,y
-         ldu   #$003F
+
+*FAProc   ldx   R$X,u        Get ptr to process to activate
+*L0D11    clrb  
+*         pshs  cc,b,x,y,u
+*         lda   P$Prior,x    Get process priority
+*         sta   P$Age,x      Save it as age (How long it's been around)
+*         orcc  #IntMasks    Shut down IRQ's
+*         ldu   #(D.AProcQ-P$Queue)  Get ptr to active process queue
+*         bra   L0D29        Go through the chain
+** Update active process queue
+**  X=Process to activate
+**  U=Current process in queue links
+*L0D1F    inc   P$Age,u      update current process age
+*         bne   L0D25        wrap?
+*         dec   P$Age,u      yes, reset it to max.
+*L0D25    cmpa  P$Age,u      match process ages??
+*         bhi   L0D2B        no, skip update
+*L0D29    leay  ,u           point Y to current process
+*L0D2B    ldu   P$Queue,u    get pointer to next process in chain
+*         bne   L0D1F        Still more in chain, keep going
+*         ldd   P$Queue,y    
+*         stx   P$Queue,y    save new process to chain
+*         std   P$Queue,x
+*         puls  cc,b,x,y,u,pc
+
+
+**************************************************
+* System Call: F$AProc
+*
+* Function: Insert process into active process queue
+*
+* Input:  X = Address of process descriptor
+*
+* Output: None (U and Y are preserved)
+*
+* Error:  CC = C bit set; B = error code
+*
+*              "An Ode to Dr. Lee"
+*             (1:27PM, Feb 23, 2006)
+*
+*   Sitting in CMPS 455, I listen to Dr. Lee,
+*   His teaching style is as awful as any can be.
+*   Operating System Principles I have seen many times before,
+*   And as a result, this class is a major bore.
+*   As he talks about file systems, I work on NitrOS-9,
+*   even though I pay no attention, I do not fall behind.
+*
+*                                  - Anonymous Student who returned
+*                                    to university to complete his
+*                                    computer science degree while working
+*                                    on The NitrOS-9 Project.
+*
+FAProc   ldx   R$X,u				get ptr to process to activate
+L021A    pshs  u,y					save U/Y on stack
+         ldu   #(D.AProcQ-P$Queue)
          bra   L0228
-L0221    ldb   P$Age,u
-         incb
-         beq   L0228
-         stb   P$Age,u
-L0228    ldu   P$Queue,u               U = proc desc
-         bne   L0221
-         ldu   #$003F
-         lda   P$Prior,x
-         sta   P$Age,x
-         orcc  #IntMasks
-L0235    leay  ,u
-         ldu   P$Queue,u
+L0221    ldb   P$Age,u				get process age
+         incb						update it
+         beq   L0228				branch if wrap
+         stb   P$Age,u				save it back to proc desc
+L0228    ldu   P$Queue,u			get pointer to queue this process queue
+         bne   L0221				branch if process is in active queue
+         ldu   #(D.AProcQ-P$Queue)
+         lda   P$Prior,x			get process priority
+         sta   P$Age,x				save it as age (How long its been around)
+         orcc  #IntMasks			mask interrupts
+L0235    leay  ,u					point Y to current process
+         ldu   P$Queue,u			get pointer to queue
          beq   L023F
-         cmpa  P$Age,u
-         bls   L0235
+         cmpa  P$Age,u				match process ages?
+         bls   L0235				no, skip update
 L023F    stu   P$Queue,x
          stx   P$Queue,y
          clrb
-         puls  pc,u,y
+         puls  pc,u,y				restore U/Y and return
+
 
 UsrSvc   leay  <L024E,pcr
          orcc  #IntMasks