From: Vincent Guittot <vincent.guittot@linaro.org>
To: Arnd Bergmann <arnd@kernel.org>
Cc: "Viresh Kumar" <viresh.kumar@linaro.org>,
"Bartosz Golaszewski" <bgolaszewski@baylibre.com>,
"Linus Walleij" <linus.walleij@linaro.org>,
"Enrico Weigelt, metux IT consult" <info@metux.net>,
"Viresh Kumar" <vireshk@kernel.org>,
"Michael S. Tsirkin" <mst@redhat.com>,
"Jason Wang" <jasowang@redhat.com>,
"Bill Mills" <bill.mills@linaro.org>,
"Alex Bennée" <alex.bennee@linaro.org>,
"Stratos Mailing List" <stratos-dev@op-lists.linaro.org>,
"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Stefan Hajnoczi" <stefanha@redhat.com>,
"Stefano Garzarella --cc virtualization @ lists .
linux-foundation . org" <sgarzare@redhat.com>,
virtualization@lists.linux-foundation.org
Subject: Re: [PATCH V3 1/3] gpio: Add virtio-gpio driver
Date: Mon, 14 Jun 2021 14:49:45 +0200 [thread overview]
Message-ID: <CAKfTPtA7p1JMP9g8o_qpZ4-2u4KVNs4VENJtrV4H7EnqrmYqHw@mail.gmail.com> (raw)
In-Reply-To: <CAK8P3a10yObfX_dFMSsqW_fGugdtz0nutJFwDB_OY0DebdGjXQ@mail.gmail.com>
On Mon, 14 Jun 2021 at 14:33, Arnd Bergmann <arnd@kernel.org> wrote:
>
> On Mon, Jun 14, 2021 at 12:23 PM Viresh Kumar <viresh.kumar@linaro.org> wrote:
> > On 10-06-21, 15:22, Arnd Bergmann wrote:
> > > Can you give an example of how this would be hooked up to other drivers
> > > using those gpios. Can you give an example of how using the "gpio-keys" or
> > > "gpio-leds" drivers in combination with virtio-gpio looks like in the DT?
> > >
> > > Would qemu simply add the required DT properties to the device node that
> > > corresponds to the virtio device in this case?
> > >
> > > From what I can tell, both the mmio and pci variants of virtio can have their
> > > dev->of_node populated, but I don't see the logic in register_virtio_device()
> > > that looks up the of_node of the virtio_device that the of_gpio code then
> > > tries to refer to.
> >
> > To be honest, I haven't tried this yet and I was expecting it to be
> > already taken care of. I was relying on the DTB automatically
> > generated by Qemu to get the driver probed and didn't have a look at
> > it as well.
> >
> > I now understand that it won't be that straight forward. The same must
> > be true for adding an i2c device to an i2c bus over virtio (The way I
> > tested that earlier was by using the sysfs file to add a device to a
> > bus).
>
> Yes, correct, we had the same discussion about i2c. Again, this is
> relatively straightforward when the controller and the device attached
> to it (i2c controller/client or gpio controller/function) are both emulated
> by qemu, but a lot harder when the controller and device are
> implemented in different programs.
>
> > This may be something lacking generally for virtio-pci thing, not
> > sure though.
>
> I think most importantly we need a DT binding to describe what device
> nodes are supposed to look like underneath a virtio-mmio or
> virtio-pci device in order for a hypervisor to pass down the
> information to a guest OS in a generic way. We can probably borrow
> the USB naming, and replace compatible="usbVID,PID" with
> compatible="virtioDID", with the device ID in hexadecimal digits,
> such as "virtio22" for I2C (virtio device ID 34 == 0x22) if we decide
> to have a sub-node under the device, or we just point dev->of_node
> of the virtio device to the platform/pci device that is its parent
> in Linux.
>
> Adding the Linux guest code to the virtio layer should be fairly
> straightforward, and I suppose it could be mostly copied from the
> corresponding code that added this for mmc in commit 25185f3f31c9
> ("mmc: Add SDIO function devicetree subnode parsing") and for USB
> in commit 69bec7259853 ("USB: core: let USB device know device
> node") and 1a7e3948cb9f ("USB: add device-tree support for
> interfaces").
And something similar is also done with SCMI protocols which are
defined in a SCMI node. A typical example:
cpu@0 {
...
clocks = <&scmi_dvfs 0>;
...
};
deviceX: deviceX@YYYYYYY {
...
clocks = <&scmi_clk 0>;
...
};
scmi: scmi {
compatible = "arm,scmi-virtio";
#address-cells = <1>;
#size-cells = <0>;
scmi_devpd: protocol@11 {
reg = <0x11>;
#power-domain-cells = <1>;
};
scmi_clk: protocol@14 {
reg = <0x14>;
#clock-cells = <1>;
};
scmi_sensors: protocol@15 {
reg = <0x15>;
#thermal-sensor-cells = <1>;
};
scmi_dvfs: protocol@13 {
reg = <0x13>;
#clock-cells = <1>;
};
};
>
> Arnd
next prev parent reply other threads:[~2021-06-14 12:50 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-10 12:09 [PATCH V3 0/3] gpio: Add virtio based driver Viresh Kumar
2021-06-10 12:16 ` [PATCH V3 1/3] gpio: Add virtio-gpio driver Viresh Kumar
2021-06-10 13:22 ` Arnd Bergmann
2021-06-10 16:00 ` Enrico Weigelt, metux IT consult
[not found] ` <01000179f6a7715c-cd106846-7770-4088-bb7c-a696bfcbf83e-000000@email.amazonses.com>
2021-06-10 17:03 ` [Stratos-dev] " Jean-Philippe Brucker
2021-06-10 19:41 ` Arnd Bergmann
2021-06-14 10:21 ` Viresh Kumar
2021-06-14 12:31 ` Arnd Bergmann
2021-06-14 12:49 ` Vincent Guittot [this message]
[not found] ` <0100017a0a9264cc-57668c56-fdbf-412a-9f82-9bf95f5c653e-000000@email.amazonses.com>
2021-06-14 12:58 ` [Stratos-dev] " Arnd Bergmann
2021-06-14 13:24 ` Vincent Guittot
2021-06-14 20:54 ` Arnd Bergmann
2021-06-15 7:30 ` Vincent Guittot
2021-06-10 15:54 ` Enrico Weigelt, metux IT consult
2021-06-10 16:57 ` Viresh Kumar
2021-06-10 20:46 ` Linus Walleij
2021-06-11 3:56 ` Viresh Kumar
2021-06-11 7:42 ` Geert Uytterhoeven
2021-06-11 8:01 ` Viresh Kumar
2021-06-11 8:22 ` Geert Uytterhoeven
2021-06-15 11:15 ` Viresh Kumar
2021-06-15 11:37 ` Geert Uytterhoeven
2021-06-15 20:03 ` Linus Walleij
2021-06-16 1:45 ` Viresh Kumar
2021-06-14 8:07 ` Enrico Weigelt, metux IT consult
2021-06-14 8:12 ` Andy Shevchenko
2021-06-14 9:14 ` Viresh Kumar
2021-06-14 9:17 ` Enrico Weigelt, metux IT consult
2021-06-14 9:52 ` Viresh Kumar
2021-06-14 9:12 ` Viresh Kumar
2021-06-14 9:29 ` Enrico Weigelt, metux IT consult
2021-06-14 8:03 ` Enrico Weigelt, metux IT consult
2021-06-14 9:24 ` Viresh Kumar
2021-06-16 3:30 ` Bjorn Andersson
2021-06-16 15:52 ` Enrico Weigelt, metux IT consult
2021-06-18 9:13 ` Linus Walleij
2021-06-21 17:25 ` Bjorn Andersson
2021-06-10 12:16 ` [PATCH V3 2/3] gpio: virtio: Add IRQ support Viresh Kumar
2021-06-10 21:30 ` Linus Walleij
2021-06-14 7:08 ` Viresh Kumar
2021-06-10 12:16 ` [PATCH V3 3/3] MAINTAINERS: Add entry for Virtio-gpio Viresh Kumar
[not found] ` <01000179f5da7763-2ea817c6-e176-423a-952e-de02443f71e2-000000@email.amazonses.com>
2021-06-10 17:40 ` [PATCH V3 1/3] gpio: Add virtio-gpio driver Jean-Philippe Brucker
2021-06-11 3:39 ` Viresh Kumar
[not found] ` <01000179f9276678-ae2bb25f-4c0c-4176-b906-650c585b9753-000000@email.amazonses.com>
2021-06-11 8:34 ` [Stratos-dev] " Arnd Bergmann
2021-06-14 5:26 ` Viresh Kumar
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