Re: [RFC PATCH v2 1/1] rpmsg: add syslog driver

Bjorn Andersson
2021-11-09T18:05:33Z

On Tue 09 Nov 00:39 PST 2021, Christian Gmeiner wrote:

> Allows the remote firmware to log into syslog.
>

This allows the remote firmware to print log messages in the kernel log,
not the syslog (although your system might inject the kernel log into
the syslog as well)

> Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
> ---
> drivers/rpmsg/Kconfig | 8 +++++
> drivers/rpmsg/Makefile | 1 +
> drivers/rpmsg/rpmsg_syslog.c | 65 ++++++++++++++++++++++++++++++++++++

drivers/rpmsg is for rpmsg bus and transport drivers. Client drivers
should live elsewhere.

But perhaps, rather than having a driver for this, you could simply use
rpmsg_char and a userspace tool; if you want to get the remote processor
logs into syslog, instead of the kernel log?

> 3 files changed, 74 insertions(+)
> create mode 100644 drivers/rpmsg/rpmsg_syslog.c
>
> diff --git a/drivers/rpmsg/Kconfig b/drivers/rpmsg/Kconfig
> index 0b4407abdf13..801f9956ec21 100644
> --- a/drivers/rpmsg/Kconfig
> +++ b/drivers/rpmsg/Kconfig
> @@ -73,4 +73,12 @@ config RPMSG_VIRTIO
> select RPMSG_NS
> select VIRTIO
>
> +config RPMSG_SYSLOG
> + tristate "SYSLOG 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.
> +
> endmenu
> diff --git a/drivers/rpmsg/Makefile b/drivers/rpmsg/Makefile
> index 8d452656f0ee..75b2ec7133a5 100644
> --- a/drivers/rpmsg/Makefile
> +++ b/drivers/rpmsg/Makefile
> @@ -9,3 +9,4 @@ obj-$(CONFIG_RPMSG_QCOM_GLINK_RPM) += qcom_glink_rpm.o
> obj-$(CONFIG_RPMSG_QCOM_GLINK_SMEM) += qcom_glink_smem.o
> obj-$(CONFIG_RPMSG_QCOM_SMD) += qcom_smd.o
> obj-$(CONFIG_RPMSG_VIRTIO) += virtio_rpmsg_bus.o
> +obj-$(CONFIG_RPMSG_SYSLOG) += rpmsg_syslog.o
> diff --git a/drivers/rpmsg/rpmsg_syslog.c b/drivers/rpmsg/rpmsg_syslog.c
> new file mode 100644
> index 000000000000..b3fdae495fd9
> --- /dev/null
> +++ b/drivers/rpmsg/rpmsg_syslog.c
> @@ -0,0 +1,65 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/rpmsg.h>
> +
> +static int rpmsg_syslog_cb(struct rpmsg_device *rpdev, void *data, int len,
> + void *priv, u32 src)
> +{
> + const char *buffer = data;
> +
> + switch (buffer[0]) {
> + case 'e':
> + dev_err(&rpdev->dev, "%s", buffer + 1);
> + break;
> + case 'w':
> + dev_warn(&rpdev->dev, "%s", buffer + 1);
> + break;
> + case 'i':
> + dev_info(&rpdev->dev, "%s", buffer + 1);
> + break;
> + default:
> + dev_info(&rpdev->dev, "%s", buffer);
> + break;
> + }
> +
> + return 0;
> +}
> +
> +static int rpmsg_syslog_probe(struct rpmsg_device *rpdev)
> +{
> + struct rpmsg_endpoint *syslog_ept;
> + struct rpmsg_channel_info syslog_chinfo = {
> + .src = 42,
> + .dst = 42,
> + .name = "syslog",
> + };
> +
> + /*
> + * Create the syslog service endpoint associated to the RPMsg
> + * device. The endpoint will be automatically destroyed when the RPMsg
> + * device will be deleted.
> + */
> + syslog_ept = rpmsg_create_ept(rpdev, rpmsg_syslog_cb, NULL, syslog_chinfo);

The rpmsg_device_id below should cause the device to probe on the
presence of a "syslog" channel announcement, so why are you creating a
new endpoint with the same here?

Why aren't you just specifying the callback of the driver?

> + if (!syslog_ept) {
> + dev_err(&rpdev->dev, "failed to create the syslog ept\n");
> + return -ENOMEM;
> + }
> + rpdev->ept = syslog_ept;
> +
> + return 0;
> +}
> +
> +static struct rpmsg_device_id rpmsg_driver_syslog_id_table[] = {
> + { .name = "syslog" },
> + { },
> +};
> +MODULE_DEVICE_TABLE(rpmsg, rpmsg_driver_syslog_id_table);
> +
> +static struct rpmsg_driver rpmsg_syslog_client = {
> + .drv.name = KBUILD_MODNAME,
> + .id_table = rpmsg_driver_syslog_id_table,
> + .probe = rpmsg_syslog_probe,
> +};
> +module_rpmsg_driver(rpmsg_syslog_client);

I would expect that building this as a module gives you complaints about
lacking MODULE_LICENSE().

Regards,
Bjorn

> --
> 2.33.1
>