Date: Fri, 17 Jan 2014 13:49:40 +0000 From: Julien Grall <julien.grall@linaro.org> To: Ian Campbell <Ian.Campbell@citrix.com> Cc: stefano.stabellini@eu.citrix.com, xen-devel@lists.xen.org, freebsd-xen@freebsd.org, freebsd-arm@FreeBSD.org, gibbs@freebsd.org, roger.pau@citrix.com Subject: Re: [RFC] Add support for Xen ARM guest on FreeBSD Message-ID: <52D934F4.709@linaro.org> In-Reply-To: <1389950962.6697.33.camel@kazak.uk.xensource.com> References: <1389733267-20822-1-git-send-email-julien.grall@linaro.org> <24851B79-7EC7-4E3A-94DB-4B9B86FDFFFC@bsdimp.com> <52D6B62A.9000208@linaro.org> <52D73C4E.2080306@freebsd.org> <52D87B15.5090208@linaro.org> <1389950962.6697.33.camel@kazak.uk.xensource.com>
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On 01/17/2014 09:29 AM, Ian Campbell wrote: > On Fri, 2014-01-17 at 00:36 +0000, Julien Grall wrote: >> >> On 01/16/2014 01:56 AM, Nathan Whitehorn wrote: >>> On the subject of simple-bus, they usually aren't necessary. For >>> example, all hypervisor devices on IBM hardware live under /vdevice, >>> which is attached to the device tree root. They don't use MMIO, so >>> simple-bus doesn't really make sense. How does Xen communicate with the >>> OS in these devices? >>> -Nathan >> >> As I understand, only the simple bus code (see simplebus_attach) is >> translating the interrupts in the device on a resource. >> So if you have a node directly attached to the root node with interrupts >> and MMIO, the driver won't be able to retrieve and translate the >> interrupts via bus_alloc_resources. > > Is the root node not considered to be a "top-level simple-bus" with a > 1:1 mapping of MMIO and interrupts? (Linux seems to treat it this way, > but I haven't trawled the docs for a spec reference to back that > behaviour up). I take it BSD doesn't do this? There is 2 different paths on FreeBSD to decode interrupt/MMIO (depending if you are under the root node or a simple-bus node). Most of the code is duplicated but there are some parts which differs (for instance interrupt decoding, see my answer to Nathan). I will look at closer to the code this week-end and see if I can fix it. -- Julien Grall
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