On Sun, 26 Apr 2020 at 14:50, Hadar Gat <Hadar.Gat@xxxxxxx> wrote: > > Hi Ard, > > > -----Original Message----- > > From: Ard Biesheuvel <ardb@xxxxxxxxxx> > > Sent: Sunday, 19 April 2020 11:55 > > > > > > > -----Original Message----- > > > > > From: Pavel Machek <pavel@xxxxxx> > > > > > Sent: Saturday, 18 April 2020 13:44 > > > > > > > > > > Hi! > > > > > > > > > > I'm configuring kernel for x86, and I get offered > > HW_RANDOM_CCTRNG > > > > > with default=Y, and help text suggesting I should enable it. > > > > > > > > > > That's... two wrong suggestions, right? > > > > > > > > > > Best regards, > > > > > Pavel > > > ... > > > > ________________________________________ > > > > From: Hadar Gat <Hadar.Gat@xxxxxxx> > > > > Sent: Saturday, April 18, 2020 11:31 PM > > > > > > > > Hi Pavel, > > > > I think you got it right.. > > > > Indeed, Arm CryptoCell CCTRNG driver couldn't be used and obviously > > useless if the Arm CryptoCell HW does not exist in the system. > > > > > > There's a delicate point here though - CryptoCell is an independent > > > hardware block, it is not tied to a particular CPU architecture. > > > There are SoCs with none-Arm architecture CPU using it. > > > > > > So I would say whatever the answer is, it should be the same for any > > > generic embedded style HW block. > > > > > > And the help text is not architecture specific anyway, is it not..? > > > > > > > Both the default y and and the help text are indeed incorrect. This should be > > fixed. We don't enable device drivers by default, and definitely not as as > > builtins. A conditional default m could be acceptable if the condition is > > sufficiently narrow. > > On one hand I totally agree with that and think the default should be N. > On the other hand, most of the HW_RANDOM drivers set the default to HW_RANDOM > and it doesn't make sense to me to do something different than almost every other HW RANDOM device. > Do I miss something here? > Yes. First of all, using 'default HW_RANDOM' everywhere makes no sense at all, but that is not your fault. If you look at drivers/char/hw_random/Kconfig, you will see that most drivers have additional depends lines, which means that 'default m' (or 'default y' in case CONFIG_HW_RANDOM=y) will only take affect if the dependency is fulfilled. It makes no sense to enable this driver on *every* single Linux system, right? Especially given that many architectures do not even support device tree, which is a prerequisite to be able to even probe. drivers/char/hw_random/Kconfig-config HW_RANDOM_INTEL drivers/char/hw_random/Kconfig- depends on (X86 || IA64) && PCI -- drivers/char/hw_random/Kconfig-config HW_RANDOM_AMD drivers/char/hw_random/Kconfig- depends on (X86 || PPC_MAPLE) && PCI -- drivers/char/hw_random/Kconfig-config HW_RANDOM_ATMEL drivers/char/hw_random/Kconfig- depends on ARCH_AT91 && HAVE_CLK && OF -- drivers/char/hw_random/Kconfig-config HW_RANDOM_BCM2835 drivers/char/hw_random/Kconfig- depends on ARCH_BCM2835 || ARCH_BCM_NSP || ARCH_BCM_5301X || \ -- drivers/char/hw_random/Kconfig-config HW_RANDOM_IPROC_RNG200 drivers/char/hw_random/Kconfig- depends on ARCH_BCM_IPROC || ARCH_BCM2835 || ARCH_BRCMSTB -- drivers/char/hw_random/Kconfig-config HW_RANDOM_GEODE drivers/char/hw_random/Kconfig- depends on X86_32 && PCI -- drivers/char/hw_random/Kconfig-config HW_RANDOM_N2RNG drivers/char/hw_random/Kconfig- depends on SPARC64 -- drivers/char/hw_random/Kconfig-config HW_RANDOM_VIA drivers/char/hw_random/Kconfig- depends on X86 -- drivers/char/hw_random/Kconfig-config HW_RANDOM_IXP4XX drivers/char/hw_random/Kconfig- depends on ARCH_IXP4XX -- drivers/char/hw_random/Kconfig-config HW_RANDOM_OMAP drivers/char/hw_random/Kconfig- depends on ARCH_OMAP16XX || ARCH_OMAP2PLUS || ARCH_MVEBU -- drivers/char/hw_random/Kconfig-config HW_RANDOM_OMAP3_ROM drivers/char/hw_random/Kconfig- depends on ARCH_OMAP3 -- drivers/char/hw_random/Kconfig-config HW_RANDOM_OCTEON drivers/char/hw_random/Kconfig- depends on CAVIUM_OCTEON_SOC -- drivers/char/hw_random/Kconfig-config HW_RANDOM_PASEMI drivers/char/hw_random/Kconfig- depends on PPC_PASEMI -- drivers/char/hw_random/Kconfig-config HW_RANDOM_VIRTIO drivers/char/hw_random/Kconfig- depends on VIRTIO -- drivers/char/hw_random/Kconfig-config HW_RANDOM_TX4939 drivers/char/hw_random/Kconfig- depends on SOC_TX4939 -- drivers/char/hw_random/Kconfig-config HW_RANDOM_MXC_RNGA drivers/char/hw_random/Kconfig- depends on SOC_IMX31 -- drivers/char/hw_random/Kconfig-config HW_RANDOM_IMX_RNGC drivers/char/hw_random/Kconfig- depends on HAS_IOMEM && HAVE_CLK -- drivers/char/hw_random/Kconfig-config HW_RANDOM_NOMADIK drivers/char/hw_random/Kconfig- depends on ARCH_NOMADIK -- drivers/char/hw_random/Kconfig-config HW_RANDOM_PSERIES drivers/char/hw_random/Kconfig- depends on PPC64 && IBMVIO -- drivers/char/hw_random/Kconfig-config HW_RANDOM_POWERNV drivers/char/hw_random/Kconfig- depends on PPC_POWERNV -- drivers/char/hw_random/Kconfig-config HW_RANDOM_HISI drivers/char/hw_random/Kconfig- depends on HW_RANDOM && ARCH_HISI -- drivers/char/hw_random/Kconfig-config HW_RANDOM_HISI_V2 drivers/char/hw_random/Kconfig- depends on HW_RANDOM && ARM64 && ACPI -- drivers/char/hw_random/Kconfig-config HW_RANDOM_ST drivers/char/hw_random/Kconfig- depends on HW_RANDOM && ARCH_STI -- drivers/char/hw_random/Kconfig-config HW_RANDOM_XGENE drivers/char/hw_random/Kconfig- depends on HW_RANDOM && ARCH_XGENE -- drivers/char/hw_random/Kconfig-config HW_RANDOM_STM32 drivers/char/hw_random/Kconfig- depends on HW_RANDOM && (ARCH_STM32 || COMPILE_TEST) -- drivers/char/hw_random/Kconfig-config HW_RANDOM_PIC32 drivers/char/hw_random/Kconfig- depends on HW_RANDOM && MACH_PIC32 -- drivers/char/hw_random/Kconfig-config HW_RANDOM_MESON drivers/char/hw_random/Kconfig- depends on HW_RANDOM -- drivers/char/hw_random/Kconfig-config HW_RANDOM_CAVIUM drivers/char/hw_random/Kconfig- depends on HW_RANDOM && PCI && (ARM64 || (COMPILE_TEST && 64BIT)) -- drivers/char/hw_random/Kconfig-config HW_RANDOM_MTK drivers/char/hw_random/Kconfig- depends on HW_RANDOM -- drivers/char/hw_random/Kconfig-config HW_RANDOM_S390 drivers/char/hw_random/Kconfig- depends on S390 -- drivers/char/hw_random/Kconfig-config HW_RANDOM_EXYNOS drivers/char/hw_random/Kconfig- depends on ARCH_EXYNOS || COMPILE_TEST -- drivers/char/hw_random/Kconfig-config HW_RANDOM_OPTEE drivers/char/hw_random/Kconfig- depends on OPTEE -- drivers/char/hw_random/Kconfig-config HW_RANDOM_NPCM drivers/char/hw_random/Kconfig- depends on ARCH_NPCM || COMPILE_TEST
