Re: [Stratos-dev] [PATCH V4 2/2] gpio: virtio: Add IRQ support

On Mon, Aug 9, 2021 at 12:47 PM Viresh Kumar via Stratos-dev
[off-list ref] wrote:

On 09-08-21, 09:55, Arnd Bergmann wrote:

quoted

Ah, right. There is already a flag that gets checked by the caller.

It does feel odd to have an empty 'irq_mask' callback though, so
maybe there is still something missing, just not what I thought.

It's probably the result of calling handle_level_irq(), which as you
said is closer to what we want, but is not exactly what we need for
this protocol.

Okay, I have tried to take care of locking as well now and used local
flags only to make sure I can depend on them to get the locking
working properly. Lets see what's broken in this now :)

I don't see anything wrong with this version, but let's see what
Marc thinks. I expect that he can still poke some holes in it, or
at least find some simplifications.

I was slightly surprised at the relation between the disabled and
masked states, where 'disable' always implies 'mask' and
'enable' always implies 'unmask', but I don't actually know how
those two are actually defined in the irqchip code in Linux, so
I assume you did this correctly.

          Arnd

On 09-08-21, 13:19, Arnd Bergmann wrote:

I don't see anything wrong with this version,

Great.

but let's see what
Marc thinks. I expect that he can still poke some holes in it, or
at least find some simplifications.

Right, though I may resend the patches properly first to make it less
confusing.

I was slightly surprised at the relation between the disabled and
masked states, where 'disable' always implies 'mask' and
'enable' always implies 'unmask', but I don't actually know how
those two are actually defined in the irqchip code in Linux, so
I assume you did this correctly.

I did have a look at the irq-core, but didn't go in real depth. I
rather saw how stuff happens at the driver's end.

- On setup-irq, the core only calls enable() and not unmask().
- On interrupt, the core calls mask(), followed by unmask() (which can
  be delayed for threaded irqs).
- On disable_irq(), the core only calls disable().
- On enable_irq(), the core only calls enable().

And so I ended up at this version :)

-- 
viresh