On Friday 30 June 2006 03:04, Uwe Bugla wrote: > First of all, what is a root bridge please? I know what a PCI-ISA > bridge is, but I stumbled across the expression "root bridge." A PCI root bridge is a device that sits between the processor and a PCI bus. On the upstream side (closer to the processor), it has some platform-specific interface. The downstream side is a standard PCI bus. Most PNP devices have some registers that control them. For example, a UART has a receive buffer, a transmit buffer, an interrupt enable register, etc. These appear at specific I/O port or MMIO addresses. Those addresses are the resources consumed by the UART. If you access those resources, the UART responds by doing something. Bridges are different. They also consume I/O port and/or MMIO address space. But some of that address space is passed through to the other side of the bridge, to the devices on the downstream bus. In ACPI, the resources that are passed to the downstream side are "consumed" by the bridge and also "produced" on the downstream side. The UART has no downstream side. It "consumes" resources but doesn't produce any. (It does produce RS-232 signals on the other side, but that's a completely different protocol and outside the scope of ACPI.) > As a consequence I do not understand in how far this "root bridge" > should be blacklisted. As far as I have received the issue the > decision of blacklisting or rejecting ACPI_PRODUCER is a EITHER-OR > one, but NOT a ALSO-THIS and ALSO-THAT one. My opinion is that we must change PNPACPI to either understand or ignore the producer resources. Matthieu posted a patch to ignore them. If we don't do this, we will have the maintenance burden of updating a blacklist whenever anybody invents a new device with producer resources. We could blacklist PNP0A03 in addition to changing PNPACPI. For the specific bug you tripped over, there's no reason to do both, but I think Shaohua is worried about other problems. For example, if the BIOS reported that the PNP0A03 device consumed I/O port 0x3f8, which is really consumed by the COM1 UART, that conflict might prevent the serial driver from using the UART. Or, somebody could make a PNP driver that claimed PNP0A03 PCI root bridges, which would conflict with the existing ACPI driver that claims PNP0A03 devices. Blacklisting PNP0A03 in PNPACPI would prevent a PNP driver from claiming it. Bjorn - To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
