Re: [virtio-comment] [PATCH V2] virtio-gpio: add the device specification

[Jason Wang <jasowang@redhat.com>]

å 2021/6/4 äå8:58, Viresh Kumar åé:
> On Fri, 4 Jun 2021 at 17:55, Enrico Weigelt, metux IT consult
> <lkml@metux.net>  wrote:
> > On 04.06.21 10:09, Viresh Kumar wrote:
> \\> > +\begin{lstlisting}
> > > +struct virtio_gpio_config {
> > > +    char name[32];
> > > +    u16 ngpio;
> > > +    u16 padding;
> > > +    u32 gpio_names_size;
> > > +    char gpio_names[0];
> > > +} __attribute__((packed));
> > > +\end{lstlisting}
> > oh no, please don't change the structs. the original one was:
> >
> > struct virtio_gpio_config {
> >           __u8    version;
> >           __u8    reserved0;
> >           __u16   num_gpios;
> >           __u32   names_size;
> >           __u8    reserved1[24];
> >           __u8    name[32];
> > };
> >
> > The version is vital - we need an upgrade path for future extensions.
> > (eg. bulk operations)
> I did wonder about how versioning works in general for virtio and couldn't find
> much for any device specification there.
>
> Does anyone know how we handle different versions of the spec? Or is it left
> for the individual protocols, GPIO in this case ?


The spec define some general features and it also allow device to 
implement its own features.

I guess in this case, it might be just a feature like VIRTIO_GPIO_F_BULK?

I'm not familiar with GPIO, but a question is, consider we have 
virtqueue, so actually bulking is already supported?

Thanks


> Sure I will add it back, just wanted to get this disucussion going.