Purpose:
Allow the user space application to create and release an rpmsg device by adding
rpmsg ioctrl to the /dev/rpmsg_ctrl interface
Aim:
The current implementation is based on the enumeration of services by the
remote processor to create a new channel and instantiate associated rpmsg device.
There is no solution to create a rpmsg channel on user application request.
If the rpmsg char driver allows adding a new endpoint over an existing channel, it
does not offer the ability to create a new one.
Adding the IOCTRL to instantiate rpmsg channels from the user application will allow
to dynamically create and destroy rpmsg devices. Some examples of use are:
- activate the service at the initiative of the application,
- remove the communication on a specific channel before entering the suspend mode,
- creating a temporary channel for debugging purposes.
Concerns:
This implementation is very simple but allows the user application to create rpmsg devices
without any limitations.
- A device can be created even if there is no match with the driver (and it is difficult to
check a match with module drivers).
- It is not really possible to add a counter to limit the number of devices, because a device
can be released by the remote side.
The question is: should we add protection? Notice that there is no protection for RPMSG_CREATE_EPT_IOCTL.
If this is not considered safe, another approach could be to create an rpmsg_ctrl API to add controls.
This API would be used by a rpmsg driver to add is own user controls, such as creating/deleting devices.
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[1]
- to test the ioctrl, a rpmsgexportdev tool is available here: https://github.com/arnopo/rpmsgexport
[1]https://patchwork.kernel.org/project/linux-remoteproc/list/?series=483793
Arnaud Pouliquen (4):
rpmsg: ctrl: Introduce RPMSG_CREATE_DEV_IOCTL
rpmsg: ctrl: Introduce RPMSG_RELEASE_DEV_IOCTL
rpmsg: ctrl: Add check on rpmsg device removability from user space
rpmsg: Add a removable attribute to the rpmsg device
drivers/rpmsg/rpmsg_core.c | 2 ++
drivers/rpmsg/rpmsg_ctrl.c | 52 +++++++++++++++++++++++++++++++++++---
include/linux/rpmsg.h | 2 ++
include/uapi/linux/rpmsg.h | 10 ++++++++
4 files changed, 62 insertions(+), 4 deletions(-)
--
2.17.1
