Re: arch/i386/kernel/mpparse.c warning fixes

[mikpe@csd.uu.se]

William Lee Irwin III writes:
 > William Lee Irwin III writes:
 > >> -	if (m->mpc_apicid > MAX_APICS) {
 > >> +	if (MAX_APICS - m->mpc_apicid <= 0) {
 > >>  		printk(KERN_WARNING "Processor #%d INVALID. (Max ID: %d).\n",
 > >>  			m->mpc_apicid, MAX_APICS);
 > >>  		--num_processors;
 > 
 > On Thu, May 22, 2003 at 06:07:43PM +0200, mikpe@csd.uu.se wrote:
 > > Eeew. Whatever the original problem is, this "fix" is just too
 > > obscure and ugly.
 > 
 > m->mpc_apicid is an 8-bit type; MAX_APICS can be 256. The above fix
 > properly compares two integral expressions of equal width.

In the original "_>_", the 8-bit mpc_apicid is implicitly converted to int
before the comparison, as part of the "integer promotions" in the "usual
arithmetic conversions" (C standard lingo). The same happens in your "_-_<=0".
So what's the benefit of the rewrite?

 > Also, as MAX_APICS-1 is reserved for the broadcast physical APIC ID
 > (it's 0xF for serial APIC and 0xFF for xAPIC) the small semantic change
 > here is correct.

No argument there, except that ">=" gets the job done in a cleaner way.