Hi Greg, On Sat, Feb 08, 2014 at 10:27:29AM -0800, Greg KH wrote: > On Sat, Feb 08, 2014 at 07:05:38PM +0800, fal...@meizu.com wrote: > > From: Wu Zhangjin <wuzhang...@gmail.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? Thanks. -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/