On Wed, Jan 30, 2013 at 12:21:21PM +0100, Julia Lawall wrote: > > > On Wed, 30 Jan 2013, Russell King - ARM Linux wrote: > > > On Wed, Jan 30, 2013 at 09:21:28AM +0100, walter harms wrote: > > > Great hit Joe :) > > > > > > Sometimes i am really surprised what code can be found > > > in the kernal and it is still working. > > > Having no clue of the code i suspect somebody tries to > > > check is mask outside the range it should read > > > PHYS_OFFSET |( SZ_64M - 1) > > > maybe someone should tell them that > > > 1+1=10 while 1|1=1 > > > It does not seem to matter here (or ... ?) > > > > This PCI host is only used on one platform (ARMCORE). > > > > For this, PHYS_OFFSET will be a value with only the top few bits of a > > 32-bit word set (such as 0xc0000000) - it's certainly not going to have > > any bits set below bit 26 on the platform this driver gets used on. > > "SZ_64M - 1" is the size of the window that RAM appears. > > > > So, _either_ logical OR or addition works. > > > > If we _did_ end up with a PHYS_OFFSET with bits less than bit 26 set > > here, we'd have bigger problems - because the base of RAM in PCI space > > will not correspond with PHYS_OFFSET and all the DMA mapping stuff breaks. > > The "problem" is that the computation is done inconsistently within the > same file. Sometimes with + and sometimes with |. And I say that is not a problem; if it _does_ become a problem, there are bigger problems that would also need solving, which given a multi-subarch kernel become a lot lot harder. Sure, we can just change them to all be a bitwise OR (sorry, not logical) but that's really only half the story. -- To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
