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

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Date:   Tue, 8 Jun 2021 08:26:05 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>
Cc:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Ohad Ben-Cohen <ohad@...ery.com>,
        linux-remoteproc <linux-remoteproc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-stm32@...md-mailman.stormreply.com,
        Julien Massot <julien.massot@....bzh>
Subject: Re: [PATCH 0/4] rpmsg: char: introduce the rpmsg-raw channel

Hi Arnaud,

Between remoteproc/RPMSG and CoreSight, I have 6 patchsets to review
(including some of your work) before getting to this one.  As such it
will take a little while.

Thanks,
Mathieu

On Mon, 7 Jun 2021 at 11:30, Arnaud Pouliquen
<arnaud.pouliquen@...s.st.com> 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
>
>
>
> Arnaud Pouliquen (4):
>   rpmsg: Introduce rpmsg_create_default_ept function
>   rpmsg: char: Add possibility to create and reuse default endpoint
>   rpmsg: char: Introduce the "rpmsg-raw" channel
>   rpmsg: char: Return error if user tries to destroy a default endpoint.
>
>  drivers/rpmsg/rpmsg_char.c | 92 +++++++++++++++++++++++++++++++++++---
>  drivers/rpmsg/rpmsg_core.c | 51 +++++++++++++++++++++
>  include/linux/rpmsg.h      | 14 ++++++
>  3 files changed, 151 insertions(+), 6 deletions(-)
>
> --
> 2.17.1
>