Re: [PATCH 0/4] rpmsg: char: introduce the rpmsg-raw channel

Julien Massot
2021-06-08T09:08:04Z

Hi,

On 6/7/21 7:30 PM, Arnaud Pouliquen wrote:
> Purpose:
> Allow the remote processor to instantiate a /dev/rpmsgX interface relying on the NS announcement
> of the "rpmsg-raw" service.
> This patchet is extracted from the series [1] with rework to add rpmsg_create_default_ept helper.
>
>
> Aim:
> There is no generic sysfs interface based on RPMsg that allows a user application to communicate
> with a remote processor in a simple way.
> The rpmsg_char dev solves a part of this problem by allowing an endpoint to be created on the
> local side. But it does not take advantage of the NS announcement mechanism implemented for some
> backends such as the virtio backend. So it is not possible to probe it from a remote initiative.
> Extending the char rpmsg device to support NS announcement makes the rpmsg_char more generic.
> By announcing a "rpmg-raw" service, the firmware of a remote processor will be able to
> instantiate a /dev/rpmsgX interface providing to the user application a basic link to communicate
> with it without any knowledge of the rpmsg protocol.
>
> Implementation details:
> - Register a rpmsg driver for the rpmsg_char driver, associated to the "rpmsg-raw" channel service.
> - In case of rpmsg char device instantiated by the rpmsg bus (on NS announcement) manage the
> channel default endpoint to ensure a stable default endpoint address, for communication with
> the remote processor.
>
> How to test it:
> - This series can be applied on git/andersson/remoteproc.git for-next branch (dc0e14fa833b)
> + the "Restructure the rpmsg char to decorrelate the control part" series[2]
>
> [1] https://patchwork.kernel.org/project/linux-remoteproc/list/?series=475217
> [2] https://patchwork.kernel.org/project/linux-remoteproc/list/?series=483793

Just tested this whole series on remoteproc for-next branch + [2].
Works for me, /dev/rpmsg0 is created on NS announcement, and removed when stopping the remote processor.
I can do a repeated series of open /read/write/close, and got EBUSY if I try to open it more than once
at a time.

Firmware used for testing is derived from:
https://github.com/zephyrproject-rtos/zephyr/tree/main/samples/subsys/ipc/openamp_rsc_table
with:
#define RPMSG_CHAN_NAME "rpmsg-raw"

Thanks Arnaud for your work.

Tested-by: Julien Massot <julien.massot@iot.bzh>

--
Julien Massot [IoT.bzh]