lkml.org 
[lkml]   [2020]   [Dec]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2 2/2] drivers: gpio: add virtio-gpio guest driver
Hello

On Sat, Dec 05, 2020 at 02:32:04PM -0500, 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:
> >
> > >
> > > 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@suse.de>
> 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@suse.de>
> Reviewed-by: Amit Shah <amit@kernel.org>
> Link: https://lore.kernel.org/r/20200831165850.26163-1-msuchanek@suse.de
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>
> 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 ...
The console driver provides early console which should initialize
without any transport. I have not tested it actually works but the code
seems to be there to support this use case.

Thanks

Michal

\
 
 \ /
  Last update: 2020-12-08 11:12    [W:1.971 / U:0.248 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site