Re: [patch 00/37] PNP resource_table cleanups, v2

[Rene Herman]

On 03-04-08 18:43, Bjorn Helgaas wrote:

> On Thursday 03 April 2008 09:54:51 am Rene Herman wrote:
> > However, now that you made me look closer and in context -- there's actually 
> > a possibly somewhat serious problem here.
> >
> > isapnp_read_resources() stores the resources as read from the hardware at 
> > the index in the table that matches the actual index in the hardware and 
> > isapnp_set_resources() stores them back into those same hardware indices.
> >
> > Now by using pnp_add_foo_resource() which just scans for the first _UNSET 
> > resource, the resources might not end up in the same linear position in 
> > table/list if intermediate resources were unset in hardware (!ret). A 
> > subsequent isapnp_set_resources() would them restore the value to the wrong 
> > hardware index.
> >
> > The IORESOURCE_ flags currently reserve too few bits (IORESOURCE_BITS,  8) 
> > to be able to store the hardware index: IORESOURCE_MEM and IORESOURCE_DMA 
> > need 2 and 1 respectively and there are 1 and 0 available respectively. It's 
> > ofcourse possible to hijack a few more bits in IORESOURCE_ flags but you're 
> > turning this into a list. I suppose the idea is to make it a simple list of 
> > struct resource, but perhaps a resource-private "driver_data" sort of field 
> > comes in handy for more than this already? Swiping more of IORESOURCE_ is a 
> > bit ugly...
> >
> > In any case, I missed this, but ISAPnP is still (at least in principle) 
> > broken with the current set therefore.
>
> Hmm...  you're right.  And I think it could bite PNPBIOS and PNPACPI
> as well -- they don't read/write hardware registers directly, but the
> firmware still depends on preserving the resource order.  I'll have to
> ponder that for a while.

Both PNPBIOS and PNPACPI should be fine it seems:

pnpbios_get_resources()
  pnpbios_read_resources_from_node()
    pnpbios_parse_allocated_resource_data()
      pnpbios_parse_allocated_irqresource()
      pnpbios_parse_allocated_dmaresource()
      pnpbios_parse_allocated_ioresource()
      pnpbios_parse_allocated_memresource()

where the latter do the same scan for the first _UNSET resource as the new 
code does. Same thing for ACPI in the path

pnpacpi_get_resources()
  pnpacpi_parse_allocated_resource()
     pnpacpi_allocated_resource()
       pnpacpi_parse_allocated_irqresource()
       pnpacpi_parse_allocated_dmaresource()
       pnpacpi_parse_allocated_ioresource()
       pnpacpi_parse_allocated_memresource()
       pnpacpi_parse_allocated_address_space()
         pnpacpi_parse_allocated_memresource()

Rene.
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