On Thursday 28 April 2016 10:12:12 Bjorn Helgaas wrote:
On Wed, Apr 27, 2016 at 06:31:29PM +0100, Lorenzo Pieralisi wrote:
On Wed, Apr 27, 2016 at 11:44:53AM -0500, Bjorn Helgaas wrote:
On Wed, Apr 27, 2016 at 12:17:58PM +0100, Lorenzo Pieralisi wrote:
On Tue, Apr 26, 2016 at 09:26:49PM -0500, Bjorn Helgaas wrote:
On Fri, Apr 15, 2016 at 07:06:37PM +0200, Tomasz Nowicki wrote:
Today we call pci_bus_assign_domain_nr() from the PCI core (from pci_create_root_bus()). This is only implemented for PCI_DOMAINS_GENERIC, but even so, it fiddles around to figure out whether to get the domain from DT or to assign a new one.
That seems backwards to me. The host bridge drivers already know where the domain should come from (ACPI _SEG, DT, etc.) and in the long term, I think they should be responsible for looking up or assigning a domain number *before* they call pci_create_root_bus().
Yes, the question still is how pci_create_root_bus() can get that value (I am pretty certain this was heavily debated in the past, which does not mean we can't give it another try).
Right, we don't have a good mechanism for passing more info into pci_create_root_bus(). Maybe the caller could fill in a struct so we have a chance to extend it without having to change all the existing callers.
I wonder if there's a design pattern we can copy, e.g., would something like the scsi_host_alloc(), scsi_add_host(), scsi_scan_host() model work here?
Yes, I think that is a good idea in general. Especially now that we have separate the ARM code from pci_common_init_dev and pci_sys_data, that can help with cleanups in the other drivers as well.
I see two common variations in other subsystems: some use a special alloc() function that you pass the size of the private data into, while others just expect you to embed a structure inside of the driver specific one allocate that separately to have the generic registration function fill out the common fields.
I have a slight preference for the second, but they are really the same thing basically.
Arnd