linux-kernel - Howto listen to/handle gpio state changes ? Re: [PATCH v2 2/2] drivers: gpio: add virtio-gpio guest driver

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Message-ID: <0080d492-2f07-d1c6-d18c-73d4204a5d40@metux.net>
Date:   Sat, 5 Dec 2020 21:15:29 +0100
From:   "Enrico Weigelt, metux IT consult" <lkml@...ux.net>
To:     "Enrico Weigelt, metux IT consult" <info@...ux.net>,
        linux-kernel@...r.kernel.org
Cc:     corbet@....net, linus.walleij@...aro.org,
        bgolaszewski@...libre.com, mst@...hat.com, jasowang@...hat.com,
        linux-doc@...r.kernel.org, linux-gpio@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        linux-riscv@...ts.infradead.org
Subject: Howto listen to/handle gpio state changes ? Re: [PATCH v2 2/2]
 drivers: gpio: add virtio-gpio guest driver

On 03.12.20 20:11, Enrico Weigelt, metux IT consult wrote:

Friends,

I've still got a problem w/ signal/irq handling:

The virtio-gpio device/host can raise a signal on line state change.
Kinda IRQ, but not actually running through real IRQs, instead by a
message running though queue. (hmm, kida MSI ? :o).

I've tried allocating an IRQ range and calling generic_handle_irq(),
but then I'm getting unhanled IRQ trap.

My hope was some gpio lib function for calling in when an line state
changes, that does all the magic (somebody listening on some gpio,
or gpio used as interrupt source), but the only thing I could find
was some helpers for gpio chips that have their own builtin
interrupt controller (VIRTIO_GPIO_EV_HOST_LEVEL).

Somehow feels that's not quite what I'm looking for.

Could anybody please give me more insights ?

--mtx

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Enrico Weigelt, metux IT consult
Free software and Linux embedded engineering
info@...ux.net -- +49-151-27565287