Hello,
This adds Virtio GPIO driver based on the proposed specification [1].
The specification for basic GPIO operations is already reviewed by Linus and Arnd, while the IRQ stuff is still under discussion and not finalized.
I am sharing the code, so everyone gets more clarity on how it will work eventually in Linux.
I have tested this patchset with Qemu guest with help of the libgpiod utility. I have also tested basic handling of interrupts on the guest side. It works as expected.
The host side virtio-backend isn't ready yet and my tests only tested the flow control between guest and host, but didn't play with real GPIO pins. That will be done once I have a working backend in place (WIP).
V4->V5: - Use ____cacheline_aligned for buffers. - Proper locking in place, which avoids the use of work-item for processing interrupts. - Separate callbacks for enable/disable of irqs. - The irq is disabled at the host only for enable/disable now, instead of mask/unmask. - mask/unmask only control the queuing of buffers now. - Use handle_level_irq() instead of handle_fasteoi_irq(). - Other minor changes.
V3->V4: - Lots of changes, as the specification changed too much. Better forget everything we have done until now :)
-- Viresh
[1] https://lists.oasis-open.org/archives/virtio-dev/202107/msg00232.html
Viresh Kumar (2): gpio: Add virtio-gpio driver gpio: virtio: Add IRQ support
MAINTAINERS | 7 + drivers/gpio/Kconfig | 10 + drivers/gpio/Makefile | 1 + drivers/gpio/gpio-virtio.c | 668 +++++++++++++++++++++++++++++++ include/uapi/linux/virtio_gpio.h | 72 ++++ 5 files changed, 758 insertions(+) create mode 100644 drivers/gpio/gpio-virtio.c create mode 100644 include/uapi/linux/virtio_gpio.h