Minimal kernel config created from bcm2709_defconfig using allnoconfig fails to compile

[simonvanderveldt]

When trying to build a minimal kernel from bcm2709_defconfig using allnoconfig the resulting configuration doesn't compile.

allnoconfig is the normal way to configure/build the most minimal working kernel. It's used in combination with a defconfig to provide the required defaults.
It can be executed in the following way to generate a minimal config based on bcm2709_defconfig:

make ARCH=arm KCONFIG_ALLCONFIG=arch/arm/configs/bcm2709_defconfig allnoconfig

Now when compiling the generated .config I ran into several of these errors:

/tmp/ccholjfv.s: Assembler messages:
/tmp/ccholjfv.s:67: Error: selected processor does not support requested special purpose register -- `mrs r3,cpsr'
/tmp/ccholjfv.s:75: Error: selected processor does not support requested special purpose register -- `msr cpsr_c,r3'

Doing a diffconfig of the configs generated by bcm2709_defconfig and allnoconfig showed that ARCH_BCM2835 was missing. Even though ARCH_BCM2835 is defined in bcm2709_defconfig it doesn't actually get activated because it's prerequisites are not met.

I was able to fix these issues by adding the following two config options to bcm2709_defconfig:

CONFIG_MMU=y
CONFIG_ARCH_MULTI_V7=y

Shall I create a PR to add them? Or is there a specific reason these two config option aren't included in bcm2709_defconfig?

Once that was fixed I ran into the following issue, for which I've not yet figured out how to fix it. Any and all suggestions are welcome :)

drivers/mmc/host/bcm2835-sdhost.c: In function 'bcm2835_sdhost_dma_complete':
drivers/mmc/host/bcm2835-sdhost.c:541:10: error: implicit declaration of function 'kmap_atomic'; did you mean 'in_atomic'? [-Werror=implicit-function-declaration]
   page = kmap_atomic(host->drain_page);
          ^~~~~~~~~~~
          in_atomic
drivers/mmc/host/bcm2835-sdhost.c:541:8: warning: assignment makes pointer from integer without a cast [-Wint-conversion]
   page = kmap_atomic(host->drain_page);
        ^
drivers/mmc/host/bcm2835-sdhost.c:552:3: error: implicit declaration of function 'kunmap_atomic'; did you mean 'in_atomic'? [-Werror=implicit-function-declaration]
   kunmap_atomic(page);
   ^~~~~~~~~~~~~
   in_atomic

[edit] I managed to fix this issue by adding CONFIG_BLOCK=y. Seems like MMC_BCM2835_SDHOST is missing this as a dependency?

This then results in the next issue:

ERROR: "snd_rawmidi_set_ops" [sound/soc/bcm/snd-soc-pisound.ko] undefined!
ERROR: "snd_rawmidi_new" [sound/soc/bcm/snd-soc-pisound.ko] undefined!
ERROR: "snd_rawmidi_transmit_peek" [sound/soc/bcm/snd-soc-pisound.ko] undefined!
ERROR: "snd_rawmidi_transmit_ack" [sound/soc/bcm/snd-soc-pisound.ko] undefined!
ERROR: "snd_rawmidi_receive" [sound/soc/bcm/snd-soc-pisound.ko] undefined!

Fixed by enabling CONFIG_SND_DRIVERS which enables the required CONFIG_SND_RAWMIDI because then the following conditions are met:

|| SND_VIRMIDI [=m] && SOUND [=y] && !M68K && !UML && SND [=m] && SND_DRIVERS [=y] && SND_SEQUENCER [=m] ||

Seems to be a missing dependency for SND_PISOUND?

[lategoodbye]

The upstream sdhost driver does the following:

#include <linux/highmem.h>

[simonvanderveldt]

The upstream sdhost driver does the following:

#include <linux/highmem.h>

@lategoodbye Would that be the correct way to fix the issue?
Asking because if I enable CONFIG_BLOCK it works, so it might just be a missing dependency in Kconfig?

[lategoodbye]

If the driver uses kmap_atomic it should include the proper header. Enabling CONFIG_BLOCK seems to hide the issue.

[simonvanderveldt]

If the driver uses kmap_atomic it should include the proper header. Enabling CONFIG_BLOCK seems to hide the issue.

OK, I'll try compiling without CONFIG_BLOCK and with the added header, will report back with the results.

[simonvanderveldt]

The upstream sdhost driver does the following:

#include <linux/highmem.h>

@lategoodbye This does indeed fix the issue. Is this something that should be fixed in this kernel tree or somewhere else?

[pelwell]

It's a downstream driver so it must be fixed here. Leave it with me.

[pelwell]

The sdhost driver change is in now.

defconfigs are defined to only store non-default settings. Because MULTI_V7=y is the default it doesn't end up in the defconfig when it is generated. There must something which is relying on MULTI_V7 that doesn't select it.

[simonvanderveldt]

The sdhost driver change is in now.

Very nice, thanks for the quick fix!

defconfigs are defined to only store non-default settings. Because MULTI_V7=y is the default it doesn't end up in the defconfig when it is generated. There must something which is relying on MULTI_V7 that doesn't select it.

I'll have a look around and will try to figure out what's causing this exactly, will report back here with my findings.

[pelwell]

Thanks - if there is a nice clean fix then we'll happily take it.

[simonvanderveldt]

@pelwell What do you think about the undefined errors from snd-soc-pisound?

ERROR: "snd_rawmidi_set_ops" [sound/soc/bcm/snd-soc-pisound.ko] undefined!
ERROR: "snd_rawmidi_new" [sound/soc/bcm/snd-soc-pisound.ko] undefined!
ERROR: "snd_rawmidi_transmit_peek" [sound/soc/bcm/snd-soc-pisound.ko] undefined!
ERROR: "snd_rawmidi_transmit_ack" [sound/soc/bcm/snd-soc-pisound.ko] undefined!
ERROR: "snd_rawmidi_receive" [sound/soc/bcm/snd-soc-pisound.ko] undefined!

I got this working by enabling CONFIG_SND_DRIVERS which enables the required CONFIG_SND_RAWMIDI because then the following conditions are met:

|| SND_VIRMIDI [=m] && SOUND [=y] && !M68K && !UML && SND [=m] && SND_DRIVERS [=y] && SND_SEQUENCER [=m] ||