Messages in this thread | | | Date | Mon, 05 Mar 2012 09:40:09 -0800 | From | David Daney <> | Subject | Re: [PATCH] drivercore: Add driver probe deferral mechanism |
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On 03/05/2012 07:47 AM, Grant Likely wrote: > Allow drivers to report at probe time that they cannot get all the resources > required by the device, and should be retried at a later time. > > This should completely solve the problem of getting devices > initialized in the right order. Right now this is mostly handled by > mucking about with initcall ordering which is a complete hack, and > doesn't even remotely handle the case where device drivers are in > modules. This approach completely sidesteps the issues by allowing > driver registration to occur in any order, and any driver can request > to be retried after a few more other drivers get probed. > > v4: - Integrate Manjunath's addition of a separate workqueue > - Change -EAGAIN to -EPROBE_DEFER for drivers to trigger deferral > - Update comment blocks to reflect how the code really works > v3: - Hold off workqueue scheduling until late_initcall so that the bulk > of driver probes are complete before we start retrying deferred devices. > - Tested with simple use cases. Still needs more testing though. > Using it to get rid of the gpio early_initcall madness, or to replace > the ASoC internal probe deferral code would be ideal. > v2: - added locking so it should no longer be utterly broken in that regard > - remove device from deferred list at device_del time. > - Still completely untested with any real use case, but has been > boot tested. > > Signed-off-by: Grant Likely<grant.likely@secretlab.ca>
Hi Grant, thanks for working on this:
Acked-by: David Daney <david.daney@cavium.com>
> Cc: Greg Kroah-Hartman<greg@kroah.com> > Cc: Mark Brown<broonie@opensource.wolfsonmicro.com> > Cc: Arnd Bergmann<arnd@arndb.de> > Cc: Dilan Lee<dilee@nvidia.com> > Cc: Manjunath GKondaiah<manjunath.gkondaiah@linaro.org> > Cc: Alan Stern<stern@rowland.harvard.edu> > Cc: Tony Lindgren<tony@atomide.com> > --- > > Hi Greg, > > This has been through several revisions now and I think it's ready to go > in. The summary from the last discussion is that users need to have the > dpm_list order adjusted if they defer themselves, but that is something > which just cannot be performed by the core code (It needs to be manipulated > mid-probe() call). > > I know that not everybody is happy with this approach, but I've yet to > see a better alternative. However, it is *really easy* to find all the > users of deferred probe since any user must return -EPROBE_DEFER explicitly. > If/when a better approach is found, all the users will be easy to find > and modify. > > If this patch is not merged, then I'm going to have to merge another round > of patches that futz with initcall ordering to get some drivers to probe > correctly. :-( > > g. > > drivers/base/base.h | 1 + > drivers/base/core.c | 2 + > drivers/base/dd.c | 138 +++++++++++++++++++++++++++++++++++++++++++++++- > include/linux/device.h | 5 ++ > include/linux/errno.h | 1 + > 5 files changed, 146 insertions(+), 1 deletions(-) >
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