PCI-Express support

[Scott Long]

M. Warner Losh wrote:
> In message: <410D51AF.4070708 at samsco.org>
>             Scott Long <scottl at samsco.org> writes:
> : M. Warner Losh wrote:
> : > In message: <410D2FEA.5050504 at samsco.org>
> : >             Scott Long <scottl at samsco.org> writes:
> : > : In order to keep the API as consistent as possible between classic 
> : > : interrupt sources and MSI sources, I'd like to add a new bus method:
> : > : 
> : > : int
> : > : bus_reserve_resource(device_t, int *start, int *end, int *count, int flags);
> : > : 
> : > : start, end, and count would be passed is as the desired range and would
> : > : map to the per-function interrupt index in MSI.  On return, the range
> : > : supported and negotiated by the OS, bus, and function would be filled
> : > : into these values.  flags would be something like SYS_RES_MESSAGE.
> : > : Internal failure of the function would be given in the return value.
> : > : Whether failure to support MSI should be given as an error code return
> : > : value can be debated.  This function will also program the MSI
> : > : configuration registers on the device to use the correct message cookie
> : > : and number of messages.
> : > 
> : > How is this different than bus_alloc_resource and adding
> : > SYS_RES_MESSAGE to the list of resources?  You can get the same
> : > information using bus_alloc_resource w/o the RF_ACTIVE flag.
> : > bus_alloc_resource also has two args, one for the type, and another
> : > for the flags (which is a different type).  start/end should be u_long
> : > to match newbus' other use of this stuff (actually, they should be a
> : > typedef, but that's a bigger change).
> : 
> : bus_alloc_resource can only allocate one resource at a time.  With MSI,
> : you can potentially allocate up to 64 interrupt vectors.  You also need
> : to know up-front how many you can allocate.  The point of
> : bus_reserve_resource is to give you this information before you make
> : your first allocation.  It also will do the initial MSI function
> : configuration that is needed.
> 
> bus_alloc_resource can allocate a range of things, so it is not
> entirely true that you can allocate only one resource at a time.  You
> can put the count in != 1 and have the same information in the reserve
> API.  Then you can ask the resource how big it is and base your
> decisions on that.  You'd then need to have some way of associating
> subranage of the range you allocated easily, which presently isn't
> that easy to do, but is needed for a lot of other things.  Doing that
> would solve the issues for msi, as well as having potential benefit to
> other bus drivers that need to be able to allocate a large range, and
> then give out subranges to its children.
> 
> Warner

Well, this is exactly the problem that I'm trying to solve.  What is
your suggestion?  Also, I'm trying to keep from modifying the
bus_setup_intr() API, so it seemed logical to keep bus_alloc_resource
and bus_setup_intr functioning exactly as they are today but still
provide the added information to the driver in an optional and
non-obtrusive way.

Scott