Date: Sat, 26 Dec 2009 01:35:14 +0100 (CET) From: Stefan Richter Subject: firewire: ohci: always use packet-per-buffer mode for isochronous reception This is a minimal change meant for the short term: Never set the ohci->use_dualbuffer flag to true. There are two reasons to do so: - Packet-per-buffer mode and dual-buffer mode do not behave the same under certain circumstances, notably if several packets are covered by a single fw_cdev_iso_packet descriptor. http://marc.info/?l=linux1394-devel&m=124965653718313 Therefore the driver stack should not silently choose one or the other mode but should leave the choice to the high-level driver (regardless if kernel driver or userspace driver). Or simply always only offer packet-per-buffer mode, since a considerable number of controllers, even current ones, does not offer dual-buffer support. - Even under circumstances where packet-per-buffer mode and dual-buffer mode behave exactly the same --- notably when used through libraw1394, libdc1394, as well as the current two kernel drivers which use isochronous reception (firewire-net and firedtv) --- we are still faced with the problem that several OHCI 1.1 controllers have bugs in dual-buffer mode. Although it looks like we have identified most of those buggy controllers by now, we cannot be quite sure about that. So, use packet-per-buffer by default from now on. This change should be followed up by a more complete solution: Either extend the in-kernel API and the userspace ABI by a choice between the two IR modes or remove all dual-buffer related code from firewire-ohci. Signed-off-by: Stefan Richter --- drivers/firewire/ohci.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) Index: linux-2.6.33-rc2/drivers/firewire/ohci.c =================================================================== --- linux-2.6.33-rc2.orig/drivers/firewire/ohci.c +++ linux-2.6.33-rc2/drivers/firewire/ohci.c @@ -2226,7 +2226,6 @@ static int ohci_queue_iso_receive_dualbu if (rest == 0) return -EINVAL; - /* FIXME: make packet-per-buffer/dual-buffer a context option */ while (rest > 0) { d = context_get_descriptors(&ctx->context, z + header_z, &d_bus); @@ -2470,7 +2469,10 @@ static int __devinit pci_probe(struct pc } version = reg_read(ohci, OHCI1394_Version) & 0x00ff00ff; +#if 0 + /* FIXME: make it a context option or remove dual-buffer mode */ ohci->use_dualbuffer = version >= OHCI_VERSION_1_1; +#endif /* dual-buffer mode is broken if more than one IR context is active */ if (dev->vendor == PCI_VENDOR_ID_AGERE &&