Re: [PATCH V5 1/2] virtio-gpio: Add the device specification

[Viresh Kumar <viresh.kumar@linaro.org>]

On 16-07-21, 21:56, Viresh Kumar wrote:
> On Fri, 16 Jul 2021 at 13:54, Arnd Bergmann <arnd@kernel.org> wrote:

> > As they are always treated as a transaction, wouldn't it be easier to have
> > a single virtqueue and make each transaction have both an input and an
> > output buffer?
> parallel
> 
> That's what I did initially (and that's we did in I2C as well), but
> then I realised
> that it may not work well with transactions done in parallel.
> 
> For example, we want to allow setting direction to input for pins 5 and 8 in
> parallel. I at that time thought that with using a single virtqueue for both
> request/response messages may block the virtqueue for further usage. But
> now that I think about it a bit more, it may not.
> 
> We should still be able to identify different response messages based on the
> address of the buffer (for example) and so what you are suggesting may
> actually work and won't be a bottleneck as I thought of it earlier.
> 
> If this works fine, I will move back to one virtqueue for all non-irq
> stuff, like I
> had until V4 and one virtqueue only for interrupt processing.

Okay, I tested this and it works. I was able to send multiple requests in
parallel and it worked out fine.

So I am going to switch back to what I had earlier, i.e. one virtqueue for all
requests originating from driver and its response from device.

And a different virtqueue for interrupts.

-- 
viresh