What does %c mean in GCC inline assembly code?

Question

I am trying to understand this inline assembly code which comes from _hypercall0 here.

asm volatile (\"call hypercall_page+%c[offset]\" \\
              


        

Answer 1

From the GCC internals documentation:

`%cdigit' can be used to substitute an operand that is a constant value without the syntax that normally indicates an immediate operand.