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rpmsg: Driver for user space endpoint interface
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This driver allows rpmsg instances to expose access to rpmsg endpoints
to user space processes. It provides a control interface, allowing
userspace to export endpoints and an endpoint interface for each exposed
endpoint.

The implementation is based on prior art by Texas Instrument, Google,
PetaLogix and was derived from a FreeRTOS performance statistics driver
written by Michal Simek.

The control interface provides a "create endpoint" ioctl, which is fed a
name, source and destination address. The three values are used to
create the endpoint, in a backend-specific way, and a rpmsg endpoint
device is created - with the three parameters are available in sysfs for
udev usage.

E.g. to create an endpoint device for one of the Qualcomm SMD channel
related to DIAG one would issue:

  struct rpmsg_endpoint_info info = { "DIAG_CNTL", 0, 0 };
  int fd = open("/dev/rpmsg_ctrl0", O_RDWR);
  ioctl(fd, RPMSG_CREATE_EPT_IOCTL, &info);

Each created endpoint device shows up as an individual character device
in /dev, allowing permission to be controlled on a per-endpoint basis.
The rpmsg endpoint will be created and destroyed following the opening
and closing of the endpoint device, allowing rpmsg backends to open and
close the physical channel, if supported by the wire protocol.

Cc: Marek Novak <marek.novak@nxp.com>
Cc: Matteo Sartori <matteo.sartori@t3lab.it>
Cc: Michal Simek <monstr@monstr.eu>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
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andersson committed Jan 18, 2017
1 parent adaa11b commit c0cdc19
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1 change: 1 addition & 0 deletions Documentation/ioctl/ioctl-number.txt
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Expand Up @@ -321,6 +321,7 @@ Code Seq#(hex) Include File Comments
0xB1 00-1F PPPoX <mailto:mostrows@styx.uwaterloo.ca>
0xB3 00 linux/mmc/ioctl.h
0xB4 00-0F linux/gpio.h <mailto:linux-gpio@vger.kernel.org>
0xB5 00-0F uapi/linux/rpmsg.h <mailto:linux-remoteproc@vger.kernel.org>
0xC0 00-0F linux/usb/iowarrior.h
0xCA 00-0F uapi/misc/cxl.h
0xCA 80-8F uapi/scsi/cxlflash_ioctl.h
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8 changes: 8 additions & 0 deletions drivers/rpmsg/Kconfig
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Expand Up @@ -4,6 +4,14 @@ menu "Rpmsg drivers"
config RPMSG
tristate

config RPMSG_CHAR
tristate "RPMSG device interface"
depends on RPMSG
help
Say Y here to export rpmsg endpoints as device files, usually found
in /dev. They make it possible for user-space programs to send and
receive rpmsg packets.

config RPMSG_QCOM_SMD
tristate "Qualcomm Shared Memory Driver (SMD)"
depends on QCOM_SMEM
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1 change: 1 addition & 0 deletions drivers/rpmsg/Makefile
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@@ -1,3 +1,4 @@
obj-$(CONFIG_RPMSG) += rpmsg_core.o
obj-$(CONFIG_RPMSG_CHAR) += rpmsg_char.o
obj-$(CONFIG_RPMSG_QCOM_SMD) += qcom_smd.o
obj-$(CONFIG_RPMSG_VIRTIO) += virtio_rpmsg_bus.o
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