Re: [PATCH v2 2/2] drivers: gpio: add virtio-gpio guest driver

[Jason Wang]

On 2020/12/6 上午4:05, Enrico Weigelt, metux IT consult wrote:
> On 05.12.20 20:32, Michael S. Tsirkin wrote:
>
> Hi,
>
> > 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.
> if VIRTIO just enables something that could be seen as library
> functions, then select should be right, IMHO.
>
> > The text near it says:
> >
> > # SPDX-License-Identifier: GPL-2.0-only
> > config VIRTIO
> >          tristate
> oh, wait, doesn't have an menu text, so we can't even explicitly enable
> it (not shown in menu) - only implicitly. Which means that some other
> option must select it, in order to become availe at all, and in order
> to make others depending on it becoming available.
>
> IMHO, therefore select is the correct approach.
>
>
> >          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.
> See above: NAK. because it can't even be enabled directly (by the user).
> If it wasn't meant otherwise, we'd have to add an menu text.
>
> > 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 ...
> When using other transports ?
> In my current project, eg. I'm using mmio - my kernel has pci completely
> disabled.
>
> > I am inclined to fix console and virtio fs to depend on VIRTIO:
> > select is harder to use correctly ...
> I don't thinkt that would be good - instead everybody should just select
> VIRTIO, never depend on it (maybe depend on VIRTIO_MENU instead)


I'm fine with either. Though I prefer to use select but it looks to me 
adding a prompt and use enable would be easier.

Thanks


> --mtx