Date: Wed, 1 Feb 2012 00:28:16 +0100 From: Marius Strobl <marius@alchemy.franken.de> To: John Baldwin <jhb@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r193833 - in head: share/man/man9 sys/kern sys/sys Message-ID: <20120131232816.GL39861@alchemy.franken.de> In-Reply-To: <201201300932.06243.jhb@freebsd.org> References: <200906091426.n59EQNRC074046@svn.freebsd.org> <20120129154124.GB18227@alchemy.franken.de> <201201300932.06243.jhb@freebsd.org>
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On Mon, Jan 30, 2012 at 09:32:06AM -0500, John Baldwin wrote: > On Sunday, January 29, 2012 10:41:24 am Marius Strobl wrote: > > On Tue, Jun 09, 2009 at 02:26:23PM +0000, John Baldwin wrote: > > > Author: jhb > > > Date: Tue Jun 9 14:26:23 2009 > > > New Revision: 193833 > > > URL: http://svn.freebsd.org/changeset/base/193833 > > > > > > Log: > > > Add support for multiple passes of the device tree during the boot-time > > > probe. The current device order is unchanged. This commit just adds the > > > infrastructure and ABI changes so that it is easier to merge later changes > > > into 8.x. > > > - Driver attachments now have an associated pass level. Attachments are > > > not allowed to probe or attach to drivers until the system-wide pass level > > > is >= the attachment's pass level. By default driver attachments use the > > > "last" pass level (BUS_PASS_DEFAULT). Driver's that wish to probe during > > > an earlier pass use EARLY_DRIVER_MODULE() instead of DRIVER_MODULE() which > > > accepts the pass level as an additional parameter. > > > - A new method BUS_NEW_PASS has been added to the bus interface. This > > > method is invoked when the system-wide pass level is changed to kick off > > > a rescan of the device tree so that drivers that have just been made > > > "eligible" can probe and attach. > > > - The bus_generic_new_pass() function provides a default implementation of > > > BUS_NEW_PASS(). It first allows drivers that were just made eligible for > > > this pass to identify new child devices. Then it propogates the rescan to > > > child devices that already have an attached driver by invoking their > > > BUS_NEW_PASS() method. It also reprobes devices without a driver. > > > - BUS_PROBE_NOMATCH() is only invoked for devices that do not have > > > an attached driver after being scanned during the final pass. > > > - The bus_set_pass() function is used during boot to raise the pass level. > > > Currently it is only called once during root_bus_configure() to raise > > > the pass level to BUS_PASS_DEFAULT. This has the effect of probing all > > > devices in a single pass identical to previous behavior. > > > > > > Reviewed by: imp > > > Approved by: re (kib) > > > > > > > What would be necessary to finally enable support for multi-pass > > probing apart from the drivers also needing to set BUS_PASS_n if > > they want to take part earlier than BUS_PASS_DEFAULT)? My > > understanding is that this is should be as simple as changing > > root_bus_configure() to return BUS_PASS_ROOT instead of > > BUS_PASS_DEFAULT but the comment above that line actually talks > > about splitting the return value (?) up somehow ... > > It will already work now without needing any changes. I have some older > patches to make x86 probe ACPI and PCI busses and bridges early and they > required no changes to the root bus. The reason for the comment is that I > eventually imagine the multiple passes being split up so that we can do other > actions after various passes are complete. For example, we might rewrite > root_bus_configure() so that it looks something like: > > void > root_bus_configure(void) > { > > /* Enumerate the device tree and reserve static resources. */ > bus_set_pass(BUS_PASS_RESOURCE); > > /* > * Now scan devices to allocate dynamic resources, possibly > * rewriting BARs, etc. > */ > /* some code that doesn't exist yet */ > > /* Now probe interrupt controllers. */ > bus_set_pass(BUS_PASS_INTERRUPT); > > /* Now kick off interrupt routing via some new bus method. */ > /* not written yet */ > > /* Finish probing everything else. */ > bus_set_pass(BUS_PASS_DEFAULT); > } > > This works because bus_set_pass() will do multiple scans of the tree, one > per configured pass level, to raise the system's pass level up to the > requested level. > Ah, great, thanks for the explanation! Marius
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