On 2020/12/7 下午9:53, Michael S. Tsirkin wrote:
On Mon, Dec 07, 2020 at 11:12:50AM +0800, Jason Wang wrote:
On 2020/12/6 上午3:32, Michael S. Tsirkin wrote:
On Sat, Dec 05, 2020 at 08:59:55AM +0100, Enrico Weigelt, metux IT consult wrote:
On 04.12.20 04:35, Jason Wang wrote:
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1615,6 +1615,15 @@ config GPIO_MOCKUP
       tools/testing/selftests/gpio/gpio-mockup.sh. Reference the
usage in
       it.
 +config GPIO_VIRTIO
+Â Â Â tristate "VirtIO GPIO support"
+Â Â Â depends on VIRTIO
Let's use select, since there's no prompt for VIRTIO and it doesn't have
any dependencies.
whoops, it's not that simple:
make: Entering directory '/home/nekrad/src/apu2-dev/pkg/kernel.apu2.git'
make[1]: Entering directory
'/home/nekrad/src/dk/DistroKit/platform-x86_64/build-target/linux-5.8.9-build'
GEN Makefile
drivers/gpu/drm/Kconfig:74:error: recursive dependency detected!
drivers/gpu/drm/Kconfig:74: symbol DRM_KMS_HELPER is selected by
DRM_VIRTIO_GPU
drivers/gpu/drm/virtio/Kconfig:2: symbol DRM_VIRTIO_GPU depends on VIRTIO
drivers/virtio/Kconfig:2: symbol VIRTIO is selected by GPIO_VIRTIO
drivers/gpio/Kconfig:1618: symbol GPIO_VIRTIO depends on GPIOLIB
drivers/gpio/Kconfig:14: symbol GPIOLIB is selected by I2C_MUX_LTC4306
drivers/i2c/muxes/Kconfig:47: symbol I2C_MUX_LTC4306 depends on I2C
drivers/i2c/Kconfig:8: symbol I2C is selected by FB_DDC
drivers/video/fbdev/Kconfig:63: symbol FB_DDC depends on FB
drivers/video/fbdev/Kconfig:12: symbol FB is selected by DRM_KMS_FB_HELPER
drivers/gpu/drm/Kconfig:80: symbol DRM_KMS_FB_HELPER depends on
DRM_KMS_HELPER
Seems that we can only depend on or select some symbol - we run into
huge trouble if thats mixed. Just changed DRM_VIRTIO_GPU to just select
VIRIO instead of depending on it, and now it works.
I've posted another patch for fixing drivers/gpu/drm/virtio/Kconfig
to use 'select' instead of 'depends on'.
It seems a bit of a mess, at this point I'm not entirely sure when
should drivers select VIRTIO and when depend on it.
The text near it says:
# SPDX-License-Identifier: GPL-2.0-only
config VIRTIO
tristate
help
This option is selected by any driver which implements the virtio
bus, such as CONFIG_VIRTIO_PCI, CONFIG_VIRTIO_MMIO, CONFIG_RPMSG
or CONFIG_S390_GUEST.
Which seems clear enough and would indicate drivers for devices *behind*
the bus should not select VIRTIO and thus presumably should "depend on" it.
This is violated in virtio console and virtio fs drivers.
For console it says:
commit 9f30eb29c514589e16f2999ea070598583d1f6ec
Author: Michal Suchanek <msuchanek@xxxxxxx>
Date: Mon Aug 31 18:58:50 2020 +0200
char: virtio: Select VIRTIO from VIRTIO_CONSOLE.
Make it possible to have virtio console built-in when
other virtio drivers are modular.
Signed-off-by: Michal Suchanek <msuchanek@xxxxxxx>
Reviewed-by: Amit Shah <amit@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20200831165850.26163-1-msuchanek@xxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
which seems kind of bogus - why do we care about allowing a builtin
virtio console driver if the pci virtio bus driver is a module?
There won't be any devices on the bus to attach to ...
For testing like switching bus from pci to MMIO?
Not sure I understand ... can you give an example?
E.g testing
modprobe -r virtio_mmio
modprobe virtio_pci
?
And for virtio fs it was like this from the beginning.
I am inclined to fix console and virtio fs to depend on VIRTIO:
select is harder to use correctly ...
Jason?
I think it works, but we need a prompt for VIRTIO otherwise there's no way
to enable it.
Thanks
That's even messier. No one needs VIRTIO core by itself - it's only used
by transports and drivers.
So we endup with two solutions (without a prompt):
1) using select, user may end up with driver without transport
2) using depends, user need to enable at least one transport
2) looks a little bit better I admit.
Thanks
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Enrico Weigelt, metux IT consult
Free software and Linux embedded engineering
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