On 8/23/21 5:14 PM, Rob Herring wrote: > On Mon, Aug 23, 2021 at 4:27 PM Frank Rowand <frowand.list@xxxxxxxxx> wrote: >> >> On 8/23/21 1:46 PM, Rob Herring wrote: >>> On Sun, Aug 22, 2021 at 11:01:15PM -0500, Frank Rowand wrote: >>>> Hi Marc, >>>> >>>> On 8/20/21 9:47 AM, Marc Zyngier wrote: >>>>> Trying to boot without SYSFS, but with OF_DYNAMIC quickly >>>>> results in a crash: >>>>> >>>>> [ 0.088460] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000070 >>>>> [...] >>>>> [ 0.103927] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 5.14.0-rc3 #4179 >>>>> [ 0.105810] Hardware name: linux,dummy-virt (DT) >>>>> [ 0.107147] pstate: 80000005 (Nzcv daif -PAN -UAO -TCO BTYPE=--) >>>>> [ 0.108876] pc : kernfs_find_and_get_ns+0x3c/0x7c >>>>> [ 0.110244] lr : kernfs_find_and_get_ns+0x3c/0x7c >>>>> [...] >>>>> [ 0.134087] Call trace: >>>>> [ 0.134800] kernfs_find_and_get_ns+0x3c/0x7c >>>>> [ 0.136054] safe_name+0x4c/0xd0 >>>>> [ 0.136994] __of_attach_node_sysfs+0xf8/0x124 >>>>> [ 0.138287] of_core_init+0x90/0xfc >>>>> [ 0.139296] driver_init+0x30/0x4c >>>>> [ 0.140283] kernel_init_freeable+0x160/0x1b8 >>>>> [ 0.141543] kernel_init+0x30/0x140 >>>>> [ 0.142561] ret_from_fork+0x10/0x18 >>>>> >>>>> While not having sysfs isn't a very common option these days, >>>>> it is still expected that such configuration would work. >>>>> >>>>> Paper over it by bailing out from __of_attach_node_sysfs() if >>>>> CONFIG_SYSFS isn't enabled. >>>> >>>> CONFIG_SYSFS should be automatically selected when CONFIG_OF_DYNAMIC >>>> is enabled, and it should not be possible to disable CONFIG_SYSFS >>>> in this case. >>> >>> That used to be true, but isn't now. >> >> OK. I agree with you, but when I investigated the original patch >> email I came to a different conclusion because of the way that I >> used make menuconfig to debug the situation. >> >> It is true when I start with a .config created from 'make qcom_defconfig', >> then select OF_UNITTEST, which is the only way I can see OF_DYNAMIC. It >> is the "if OF_UNITTEST" that means SYSFS can not be disabled. > > Not really. Disabling SYSFS has nothing to do with the DT code. It's > not super easy though. It required setting EXPERT and disabling > CONFIGFS_FS and things selecting it (PCIE endpoint and USB gadget). > >> If I start with the .config that Marc supplied, then make menuconfig >> still does not show the OC_DYNAMIC option, but leaves it set since >> it was already set. In this case SYSFS remains disabled because >> OF_UNITTEST is also disabled. > > I don't see the relationship between SYSFS and OF_UNITTEST. I don't either. Other than the results of experimenting showing that if I enable OF_UNITTEST then I can no long disable SYSFS. > >> Using '/OF_DYNAMIC' from within make menuconfig, to get more info >> about OF_DYNAMIC tells me that the prompt for OF_DYNAMIC is visible >> if OF && OF_UNITTEST. This is due to the "if OF_UNITTEST" in line 58 >> of drivers/of/Kconfig in the OF_DYNAMIC specification. >> >> Thus I can't figure out how to use make menuconfig to set OF_DYNAMIC >> without setting OF_UNITTEST. I tried setting OF_UNITTEST, then setting >> OF_DYNAMIC, saving the changes, then another make menuconfig to >> disable OF_UNITTEST, which then has the side effect of unsetting >> OF_DYNAMIC. > > Selecting OF_OVERLAY also. > >> Would you accept a patch that removes the "if OF_UNITTEST" from >> the Kconfig entry for OF_DYNAMIC? > > I guess. The purpose of making it visible was for compile testing, so > maybe make it 'if COMPILE_TEST' instead? After thinking a bit, I didn't like my original suggestion. I'll think some more, but I think that I will not follow up on my original suggestion. > > > Looking at occurrences of CONFIG_OF_DYNAMIC, there's more than I'd > like. This for example is a common pattern: > > drivers/spi/spi.c: if (IS_ENABLED(CONFIG_OF_DYNAMIC)) > drivers/spi/spi.c- > WARN_ON(of_reconfig_notifier_register(&spi_of_notifier)); > > Really, of_reconfig_notifier_register() should just return 0 if > !IS_ENABLED(CONFIG_OF_DYNAMIC). I'll add researching use of CONFIG_OF_DYNAMIC to my todo list. -Frank > > Rob >
