Re: [parisc-linux] Untested port of parisc_device to generic device interface

From: Adam J. Richter (
Date: Sun Nov 10 2002 - 00:20:46 EST

On Sat, Nov 09, 2002 at 05:21:50AM +0000, Matthew Wilcox wrote about
generic device models:
> And, for gods sake, don't fuck it up by integrating it with USB too early
> in the game.

        Without rewriting everything, I could see creating a common
device container for devices connected directly to the CPU's memory,
IO or interrupt busses (PCI, ISA, sbus, etc.) so as not to increase
the memory size of device and device_driver for non-mapped device
types (USB, firewire, SCSI, etc.). More importantly, this change
would provide some type checking for operations that are really only
meaningful on CPU mapped devices, such as the "generic"
dma_{alloc,free}_consistent() and related functions. I imagine
something like this:

struct cpu_mapped_device {
        dma_addr_t dma_mask;
        /* Initialized from parent->dma_mask and driver->dma_restrictions. */
        void *prealloc_vaddr;
        void *prealloc_busaddr;
        struct device device;

struct cpu_mapped_driver {
        struct io_restrictions *dma_restrictions;
        int prealloc_consistent;
        int fake_consistent_ok : 1;
        struct device_driver driver;

struct device {
        struct resource_list *resources;
        /* For automatic release of memory ranges, IO ports, DMA channels,
           IRQ's, SCSI ID's, SCSI LUN's within an ID, USB device ID's,
           etc. (but not USB hub ports, and PCMCIA slots, which we can
           released before ->remove() is called). */

        dma_pool_t dma_stub_pool[2];
        struct cpu_mapped_device *dma_dev;
        /* Points to the cpu_mapped_device that we are embedded in for PCI,
           ISA, and other cpu mapped devices. Points to the parent
           cpu mapped device for others, such as the USB controller for a
           USB network interface. Will be used for allocating DMA gather
           scatter stubs when allocating skbuff's, bio's, scsi_request's,
           USB request blocks, etc., eliminating another set of error
           branches. */

Adam J. Richter __ ______________ 575 Oroville Road \ / Miplitas, California 95035
+1 408 309-6081 | g g d r a s i l United States of America
                         "Free Software For The Rest Of Us."
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This archive was generated by hypermail 2b29 : Fri Nov 15 2002 - 22:00:19 EST