Re: [PATCH] scripts/dtc: dt_to_config - report kernel config options for a devicetree

[Rob Herring]

On Thu, Apr 28, 2016 at 4:46 PM, Frank Rowand <frowand.list@xxxxxxxxx> wrote:
> From: Frank Rowand <frank.rowand@xxxxxxxxxxx>
>
> Determining which kernel config options need to be enabled for a
> given devicetree can be a painful process.  Create a new tool to
> find the drivers that may match a devicetree node compatible,
> find the kernel config options that enable the driver, and
> optionally report whether the kernel config option is enabled.

I would find this more useful to output a config fragment with all the
options enabled. The hard part there is enabling the options a given
option is dependent on which I don't think kbuild takes care of.

> Signed-off-by: Gaurav Minocha <gaurav.minocha.os@xxxxxxxxx>
> Signed-off-by: Frank Rowand <frank.rowand@xxxxxxxxxxx>
>
> ---
>  scripts/dtc/dt_to_config | 1061 +++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 1061 insertions(+)
>
> Index: b/scripts/dtc/dt_to_config
> ===================================================================
> --- /dev/null
> +++ b/scripts/dtc/dt_to_config
> @@ -0,0 +1,1061 @@
> +#!/usr/bin/perl

I don't do perl...

> +
> +#   Copyright 2016 by Frank Rowand
> +# Å Copyright 2016 by Gaurav Minocha
     ^
Is this supposed to be a copyright symbol?

> +#
> +# This file is subject to the terms and conditions of the GNU General Public
> +# License v2.

[...]

> +# ----- magic compatibles, do not have a driver
> +#
> +# Will not search for drivers for these compatibles.
> +
> +%compat_white_list = (
> +       'fixed-partitions'      => '1',

Enabling CONFIG_MTD would be useful.

> +       'none'                  => '1',

Is this an actual string used somewhere?

> +       'pci'                   => '1',

ditto?

> +       'simple-bus'            => '1',
> +);
> +
> +# magic compatibles, have a driver
> +#
> +# Will not search for drivers for these compatibles.
> +# Will instead use the drivers and config options listed here.
> +#
> +# If you add an entry to this hash, add the corresponding entry
> +# to %driver_config_hard_code_list.
> +#
> +# These compatibles have a very large number of false positives.

What does this mean?

> +#
> +# 'hardcoded_no_driver' is a magic value.  Other code knows this
> +# magic value.  Do not use 'no_driver' here!
> +#
> +# TODO: Revisit each 'hardcoded_no_driver' to see how the compatible
> +#       is used.  Are there drivers that can be provided?
> +
> +%driver_hard_code_list = (
> +       'cache'                 => ['hardcoded_no_driver'],
> +       'eeprom'                => ['hardcoded_no_driver'],
> +       'gpio'                  => ['hardcoded_no_driver'],
> +       'gpios'                 => ['drivers/leds/leds-tca6507.c'],
> +       'gpio-keys'             => ['drivers/input/keyboard/gpio_keys.c'],
> +       'i2c-gpio'              => ['drivers/i2c/busses/i2c-gpio.c'],
> +       'isa'                   => ['arch/mips/mti-malta/malta-dt.c',
> +                                    'arch/x86/kernel/devicetree.c'],
> +       'led'                   => ['hardcoded_no_driver'],
> +       'm25p32'                => ['hardcoded_no_driver'],
> +       'm25p64'                => ['hardcoded_no_driver'],
> +       'm25p80'                => ['hardcoded_no_driver'],
> +       'mtd_ram'               => ['drivers/mtd/maps/physmap_of.c'],
> +       'pwm-backlight'         => ['drivers/video/backlight/pwm_bl.c'],
> +       'spidev'                => ['hardcoded_no_driver'],
> +       'syscon'                => ['drivers/mfd/syscon.c'],
> +       'tlv320aic23'           => ['hardcoded_no_driver'],
> +       'wm8731'                => ['hardcoded_no_driver'],
> +);
> +
> +%driver_config_hard_code_list = (
> +
> +       # this one needed even if %driver_hard_code_list is empty
> +       'no_driver'                             => ['no_config'],
> +       'hardcoded_no_driver'                   => ['no_config'],
> +
> +       'drivers/leds/leds-tca6507.c'           => ['CONFIG_LEDS_TCA6507'],
> +       'drivers/input/keyboard/gpio_keys.c'    => ['CONFIG_KEYBOARD_GPIO'],
> +       'drivers/i2c/busses/i2c-gpio.c'         => ['CONFIG_I2C_GPIO'],
> +       'arch/mips/mti-malta/malta-dt.c'        => ['obj-y'],
> +       'arch/x86/kernel/devicetree.c'          => ['CONFIG_OF'],
> +       'drivers/mtd/maps/physmap_of.c'         => ['CONFIG_MTD_PHYSMAP_OF'],
> +       'drivers/video/backlight/pwm_bl.c'      => ['CONFIG_BACKLIGHT_PWM'],
> +       'drivers/mfd/syscon.c'                  => ['CONFIG_MFD_SYSCON'],

I don't understand why some of these are not searchable by compatible strings.

> +
> +       # drivers/usb/host/ehci-ppc-of.c
> +       # drivers/usb/host/ehci-xilinx-of.c
> +       #  are included from:
> +       #    drivers/usb/host/ehci-hcd.c
> +       #  thus the search of Makefile for the included .c files is incorrect
> +       # ehci-hcd.c wraps the includes with ifdef CONFIG_USB_EHCI_HCD_..._OF
> +       #
> +       # similar model for ohci-hcd.c (but no ohci-xilinx-of.c)
> +       #
> +       # similarly, uhci-hcd.c includes uhci-platform.c
> +
> +       'drivers/usb/host/ehci-ppc-of.c'        => ['CONFIG_USB_EHCI_HCD',
> +                                                   'CONFIG_USB_EHCI_HCD_PPC_OF'],
> +       'drivers/usb/host/ohci-ppc-of.c'        => ['CONFIG_USB_OHCI_HCD',
> +                                                   'CONFIG_USB_OHCI_HCD_PPC_OF'],
> +
> +       'drivers/usb/host/ehci-xilinx-of.c'     => ['CONFIG_USB_EHCI_HCD',
> +                                                   'CONFIG_USB_EHCI_HCD_XILINX'],
> +
> +       'drivers/usb/host/uhci-platform.c'      => ['CONFIG_USB_UHCI_HCD',
> +                                                   'CONFIG_USB_UHCI_PLATFORM'],
> +
> +       # scan_makefile will find only one of these config options:
> +       #    ifneq ($(CONFIG_SOC_IMX6)$(CONFIG_SOC_LS1021A),)
> +       'arch/arm/mach-imx/platsmp.c'           => ['CONFIG_SOC_IMX6 && CONFIG_SMP',
> +                                                   'CONFIG_SOC_LS1021A && CONFIG_SMP'],

These will never get updated when the files or config options change.
Conversely, how do I know if I need to add something here? Is this
list complete or based on testing some set of dts files. IMO, this
list has to go to merge this.

> +);
> +
> +
> +# 'virt/kvm/arm/.*' are controlled by makefiles in other directories,
> +# using relative paths, such as 'KVM := ../../../virt/kvm'.  Do not
> +# add complexity to find_kconfig() to deal with this.  There is a long
> +# term intent to change the kvm related makefiles to the normal kernel
> +# style.  After that is done, this entry can be removed from the
> +# driver_black_list.
> +
> +@driver_black_list = (
> +       'virt/kvm/arm/.*',
> +);

A small number of exceptions like this I could stomach.

The rest is just write-only language nonsense...

Rob