On Thursday 17 January 2008 09:16:51 am Russell King wrote: > On Thu, Jan 17, 2008 at 09:07:29AM -0700, Bjorn Helgaas wrote: > > On Wednesday 16 January 2008 01:14:38 pm Russell King wrote: > > > On Wed, Jan 16, 2008 at 12:59:27PM -0700, Bjorn Helgaas wrote: > > > > On Wednesday 16 January 2008 11:39:34 am Russell King wrote: > > > > > On Wed, Jan 16, 2008 at 10:05:41AM -0700, Bjorn Helgaas wrote: > > > > > > When 8250_pnp discovers COM ports, we only get the correct ttyS names > > > > > > by accident -- we rely on serial8250_isa_init_ports(), which discovers > > > > > > the COM ports earlier using the addresses in SERIAL_PORT_DFNS. > > > > > > > > > > It's not by accident but by design. It's quite intentional that it > > > > > remembers the addresses of serial ports, and if another port is > > > > > registered later with the same base address, it gets the same name. > > > > > > > > It's certainly by design that if we register a port twice, it gets > > > > the same name both times. > > > > > > Incorrect - if it's not detected first time around (eg, the port isn't > > > accessible at that time), its slot will still be reserved due to the > > > way slots are given out. > > > > > > Slots are given to users in order of: > > > > > > 1. does the IO type and base address of a previously known port match > > > the new port? If so, use that. > > > 2. do we have a slot which has never been used - use that. > > > 3. find the first slot which is not currently in use. > > > > > > So, the only way we'd get the first set of ttyS slots used is if all of > > > the following are true: > > > > > > a) the ISA probe doesn't detect them > > > b) some other driver registers many ports which don't correspond with any > > > of the ISA listed addresses and we run out of empty slots > > > c) 8250_pnp initialises after this driver > > > > > > (c) is unlikely, except in the modular case - we explicitly list 8250_pnp > > > immediately after the 8250 driver so that it gets first call on the > > > slots during initialisation time, before we probe for PCI devices. > > > > Let me back up a minute. I was merely trying to make the point that > > if we skip the ISA probe (which uses SERIAL_PORT_DFNS), the 8250_pnp > > probe will discover the COM ports but won't necessarily name them the > > way we expect (e.g., http://lkml.org/lkml/2007/8/10/409). > > It would be useful to see the full kernel messages to diagnose what's > going on. Given that there's no changes to the serial probing code > (or even the code which allocates slots) there's something fishy going > on. Are they using mainline kernels or do the kernels they're using > have some other changes which aren't in mainline? I'm not trying to fix a current problem. The URL I quoted was from 2.6.22, where we didn't do the ISA probe. We fixed that problem by putting the ISA probe back the way it was in 2.6.21. But I do still want to remove the dependency between the ISA probe and the 8250_pnp probe because it seems like it's more complicated than it needs to be, and if we could figure out a way to safely remove the ISA probe, it would help solve the IRDA issues. Bjorn - To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
