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Date:   Mon, 7 Dec 2020 11:16:16 +0800
From:   Jason Wang <>
To:     "Enrico Weigelt, metux IT consult" <>,
        "Michael S. Tsirkin" <>
Cc:     "Enrico Weigelt, metux IT consult" <>,,,,,,,,,,
Subject: Re: [PATCH v2 2/2] drivers: gpio: add virtio-gpio guest driver

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
>>            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 <>
>> 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 <>
>>      Reviewed-by: Amit Shah <>
>>      Link:
>>      Signed-off-by: Greg Kroah-Hartman <>
>> 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.


> --mtx

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