On 4/29/2026 10:23 PM, Shenwei Wang wrote:
-----Original Message-----
From: Mathieu Poirier <[email protected]>
Sent: Wednesday, April 29, 2026 10:42 AM
To: Shenwei Wang <[email protected]>
Cc: Andrew Lunn <[email protected]>; Padhi, Beleswar <[email protected]>; Linus
Walleij <[email protected]>; Bartosz Golaszewski <[email protected]>; Jonathan
Corbet <[email protected]>; Rob Herring <[email protected]>; Krzysztof Kozlowski
<[email protected]>; Conor Dooley <[email protected]>; Bjorn Andersson
<[email protected]>; Frank Li <[email protected]>; Sascha Hauer
<[email protected]>; Shuah Khan <[email protected]>; linux-
[email protected]; [email protected]; [email protected];
Pengutronix Kernel Team <[email protected]>; Fabio Estevam
<[email protected]>; Peng Fan <[email protected]>;
[email protected]; [email protected];
[email protected]; [email protected]; dl-linux-imx <linux-
[email protected]>; Bartosz Golaszewski <[email protected]>
Subject: [EXT] Re: [PATCH v13 3/4] gpio: rpmsg: add generic rpmsg GPIO driver
On Tue, Apr 28, 2026 at 03:24:59PM +0000, Shenwei Wang wrote:
-----Original Message-----
From: Andrew Lunn <[email protected]>
Sent: Monday, April 27, 2026 3:49 PM
To: Shenwei Wang <[email protected]>
Cc: Padhi, Beleswar <[email protected]>; Linus Walleij
<[email protected]>; Bartosz Golaszewski <[email protected]>; Jonathan
Corbet <[email protected]>; Rob Herring <[email protected]>; Krzysztof
Kozlowski <[email protected]>; Conor Dooley <[email protected]>;
Bjorn Andersson <[email protected]>; Mathieu Poirier
<[email protected]>; Frank Li <[email protected]>; Sascha
Hauer <[email protected]>; Shuah Khan
<[email protected]>; [email protected]; linux-
[email protected]; [email protected]; Pengutronix
Kernel Team <[email protected]>; Fabio Estevam
<[email protected]>; Peng Fan <[email protected]>;
[email protected]; linux- [email protected];
[email protected]; linux-arm- [email protected];
dl-linux-imx <[email protected]>; Bartosz Golaszewski
<[email protected]>
Subject: [EXT] Re: [PATCH v13 3/4] gpio: rpmsg: add generic rpmsg
GPIO driver
struct virtio_gpio_response {
__u8 status;
__u8 value;
};
It is the same message format. Please see the message definition
(GET_DIRECTION) below:
+ +-----+-----+-----+-----+-----+----+
+ |0x00 |0x01 |0x02 |0x03 |0x04 |0x05|
+ | 1 | 2 |port |line | err | dir|
+ +-----+-----+-----+-----+-----+----+
Sorry, but i don't see how two u8 vs six u8 are the same message format.
Some changes to the message format are necessary.
Virtio uses two communication channels (virtqueues): one for requests and
replies, and a second one for events.
In contrast, rpmsg provides only a single communication channel, so a
type field is required to distinguish between different kinds of messages.
Since rpmsg replies and events share the same message format, an additional
line is introduced to handle both cases.
Finally, rpmsg supports multiple GPIO controllers, so a port field is added to
uniquely identify the target controller.
I have commented on this before - RPMSG is already providing multiplexing
capability by way of endpoints. There is no need for a port field. One
endpoint,
one GPIO controller.
You still need a way to let the remote side know which port the endpoint maps
to,
About this, we only need to do this because you are defining the gpio
controller instances "statically" in the device tree. I understand gpio
nodes can act as providers, but I do not see any device referencing the
gpio nodes you are defining in the device tree. If that is the case, you
can completely remove the nodes from device tree, and "dynamically"
announce the existence of these nodes from the firmware itself
(similar to what is done for rpmsg-tty currently). In response to that
announce message, Linux could send the "ept" it allocated for the
controller. That way, Linux only cares about "ept" and there is no need
to maintain port 'idx' info anywhere in the Linux side anymore.
Thanks,
Beleswar
