How can I use kbgetc in xv6 - xv6

Question

I want use kbdgetc() in user mode.
I need to use it to program a vim-like software in xv6.
I try to use kernel mode, but I totally don't know how to do it.

Answer 1

I guess that you want some non-buffering reading on fd 0?
To achieve this behavior, you can modify consoleintr function that is responsible of it.
First add some variable internal to the kernel to disable or not buffering.
Lets call it non_buffering and set its default values to 0.
Then add a system call to change this value (or modify an existing, as you want)
Change consoleintr this way (modification is line 221):
191 void
192 consoleintr(int (*getc)(void))
193 {
194 int c, doprocdump = 0;
195
196 acquire(&cons.lock);
197 while((c = getc()) >= 0){
198 switch(c){
....
216 default:
217 if(c != 0 && input.e-input.r < INPUT_BUF){
218 c = (c == '\r') ? '\n' : c;
219 input.buf[input.e++ % INPUT_BUF] = c;
220 consputc(c);
/* NON_BUFFERING added here */
221 if(non_buffering || c == '\n' || c == C('D') || input.e == input.r+INPUT_BUF){
222 input.w = input.e;
223 wakeup(&input.r);
224 }
225 }
226 break;
227 }
228 }
229 release(&cons.lock);
230 if(doprocdump) {
231 procdump(); // now call procdump() wo. cons.lock held
232 }
233 }