Am 02.06.2015 um 10:48 schrieb Linus Walleij: > On Mon, May 25, 2015 at 4:53 PM, Tomeu Vizoso > <tomeu.vizoso@xxxxxxxxxxxxx> wrote: > >> have looked into ordered probing as a >> better way of solving this than moving nodes around in the DT or playing with >> initcall levels. >> >> While reading the thread [1] that Alexander Holler started with his series to >> make probing order deterministic, it occurred to me that it should be possible >> to achieve the same by registering devices as they are referenced by other >> devices. > > This is pretty cool, but a too local solution to a global problem. > > Deferred probe and initcall reordering, silly as they may seem, > does not require you to use device tree. > > The real solution, which I think I pointed out already when we > added deferred probe, is to put dependency graphs in the drivers > and have the kernel device driver core percolate dependecies by > walking the graph on probing driver, removing driver (usually the > inverse use case), [runtime] suspend and [runtime] resumeing > a driver. Possibly the dependencies will even be different > depending on use case. > > This is what systemd is doing in userspace for starting services: > ask for your dependencies and wait for them if they are not > there. So drivers ask for resources and wait for them. It also > needs to be abstract, so for example we need to be able to > hang on regulator_get() until the driver is up and providing that > regulator, and as long as everything is in slowpath it should > be OK. (And vice versa mutatis mutandis for clk, gpio, pin > control, interrupts (!) and DMA channels for example.) > > > So if this should be solved it should be solved in an abstract way > in the device driver core available for all, then have calls calling > out to DT, ACPI, possibly even PCI or USB (as these > enumerate devices themselves) to obtain a certain > dependency. I suggest to start with making it possible to identify (at least most) drivers. I've already posted a patch for that around a year ago and now Tomeu did almost the same. However one wants to make a deterministic order to load drivers, there will be always the need to know which drivers one has to sort. Regards, Alexander Holler _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
