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Message-ID: <20140814041834.GA7727@kroah.com> Date: Thu, 14 Aug 2014 12:18:34 +0800 From: Greg KH <gregkh@...uxfoundation.org> To: Dmitry Torokhov <dmitry.torokhov@...il.com> Cc: falcon@...zu.com, linux-kernel@...r.kernel.org Subject: Re: [PATCH 1/2] async: async device driver probing On Wed, Aug 13, 2014 at 03:10:44PM -0700, Dmitry Torokhov wrote: > On Thu, Aug 14, 2014 at 06:02:23AM +0800, Greg KH wrote: > > On Wed, Aug 13, 2014 at 10:20:33AM -0700, Dmitry Torokhov wrote: > > > Hi Greg, > > > > > > On Sat, Feb 08, 2014 at 10:27:29AM -0800, Greg KH wrote: > > > > February? That's an old thread to dig up... > > Well, yes ;) > > > > > > > > > On Sat, Feb 08, 2014 at 07:05:38PM +0800, falcon@...zu.com wrote: > > > > > From: Wu Zhangjin <wuzhangjin@...il.com> > > > > > > > > > > [*Note*: NOT applicable, only for comments.] > > > > > > > > > > To async the slow driver probing function of some devices, the device probing > > > > > support is modified to support async scheduling. > > > > > > > > > > In order to async your driver probing function, please mask the async_probe > > > > > flag to 1, and to make sure one asynced probing is executed before an specified > > > > > point, please call async_synchronize_full() in that point.. > > > > > > > > > > Usage: > > > > > > > > > > static struct i2c_driver test_driver = { > > > > > .driver = { > > > > > .name = TEST_DEV_NAME, > > > > > .owner = THIS_MODULE, > > > > > + .async_probe = 1, > > > > > }, > > > > > > > > Why is this needed, we have defered probing and the container stuff, so > > > > what problem is this solving? > > > > > > Deferred probing only helps if resources are not ready yet, but > > > sometimes we have a slow(ish) device which initialization stalls probing > > > the rest of the system. For example a touchpad can take up to a second > > > to calibrate itself after reset. One could try scheduling reset > > > asynchronously, or try to offload it to open(), but that is not always > > > best: > > > > > > 1. Manual async: what to do when reset fails? Ideally we do not want to > > > leave driver half-way bound with device not operable, but much rather > > > signal the rest of the system that binding of the device failed and > > > release all resources. > > > > > > 2. Offload to open: the same issue as with manually doing async reset, > > > plus sometimes we do not know all parameters that we should create input > > > device with until after we reset physical device and queried it for > > > capabilities. > > > > > > Marking a driver to tell device core to execute probe asynchronously [at > > > boot time] seems like a very appealing feature from driver author POV. > > > > > > What is the container stuff you mention? > > > > drivers/base/container.c > > I am not sure how that would help in the scenario described above, as it > seems ACPI specific... It is? I thought the drm people were using it on ARM. I really don't know, sorry, don't have the chance to check it right now... greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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