Re: [PATCH v2 5/8] rpmsg: introduce reserved rpmsg driver for ns announcement

[Arnaud POULIQUEN]

Hi mathieu,

On 9/19/20 1:10 AM, Mathieu Poirier wrote:
> Hey Arnaud,
> 
> On Tue, Aug 25, 2020 at 06:49:04PM +0200, Arnaud Pouliquen wrote:
>> The name service announcement should not be linked to the RPMsg virtio bus
>> but to the RPMsg protocol itself.
>>
>> This patch proposes to break the dependency with the RPmsg virtio bus by
>> the introduction of the reserved RPMsg name service driver which will be in
>> charge of managing the RPMsg name service announcement.
>>
>> This first patch only implements the probe and the RPMsg endpoint to
>> manage create and release channels remote requests.
>>
>> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@xxxxxx>
>> ---
>>  drivers/rpmsg/Kconfig          |   8 ++
>>  drivers/rpmsg/Makefile         |   1 +
>>  drivers/rpmsg/rpmsg_internal.h |  17 +++++
>>  drivers/rpmsg/rpmsg_ns.c       | 135 +++++++++++++++++++++++++++++++++
>>  4 files changed, 161 insertions(+)
>>  create mode 100644 drivers/rpmsg/rpmsg_ns.c
>>
>> diff --git a/drivers/rpmsg/Kconfig b/drivers/rpmsg/Kconfig
>> index f96716893c2a..c3fc75e6514b 100644
>> --- a/drivers/rpmsg/Kconfig
>> +++ b/drivers/rpmsg/Kconfig
>> @@ -15,6 +15,14 @@ config RPMSG_CHAR
>>  	  in /dev. They make it possible for user-space programs to send and
>>  	  receive rpmsg packets.
>>  
>> +config RPMSG_NS
>> +	tristate "RPMSG name service announcement"
>> +	depends on RPMSG
>> +	help
>> +	  Say Y here to enable the support of the name service announcement
>> +	  channel that probes the associated RPMsg device on remote endpoint
>> +	  service announcement.
>> +
>>  config RPMSG_MTK_SCP
>>  	tristate "MediaTek SCP"
>>  	depends on MTK_SCP
>> diff --git a/drivers/rpmsg/Makefile b/drivers/rpmsg/Makefile
>> index ffe932ef6050..8d452656f0ee 100644
>> --- a/drivers/rpmsg/Makefile
>> +++ b/drivers/rpmsg/Makefile
>> @@ -1,6 +1,7 @@
>>  # SPDX-License-Identifier: GPL-2.0
>>  obj-$(CONFIG_RPMSG)		+= rpmsg_core.o
>>  obj-$(CONFIG_RPMSG_CHAR)	+= rpmsg_char.o
>> +obj-$(CONFIG_RPMSG_NS)		+= rpmsg_ns.o
>>  obj-$(CONFIG_RPMSG_MTK_SCP)	+= mtk_rpmsg.o
>>  qcom_glink-objs			:= qcom_glink_native.o qcom_glink_ssr.o
>>  obj-$(CONFIG_RPMSG_QCOM_GLINK) += qcom_glink.o
>> diff --git a/drivers/rpmsg/rpmsg_internal.h b/drivers/rpmsg/rpmsg_internal.h
>> index d5ab286d0e5e..641b48f6bf2a 100644
>> --- a/drivers/rpmsg/rpmsg_internal.h
>> +++ b/drivers/rpmsg/rpmsg_internal.h
>> @@ -102,4 +102,21 @@ static inline int rpmsg_chrdev_register_device(struct rpmsg_device *rpdev)
>>  	return rpmsg_register_device(rpdev);
>>  }
>>  
>> +/**
>> + * rpmsg_ns_register_device() - register name service device based on rpdev
>> + * @rpdev: prepared rpdev to be used for creating endpoints
>> + *
>> + * This function wraps rpmsg_register_device() preparing the rpdev for use as
>> + * basis for the rpmsg name service device.
>> + */
>> +static inline int rpmsg_ns_register_device(struct rpmsg_device *rpdev)
>> +{
>> +	strcpy(rpdev->id.name, "rpmsg_ns");
>> +	rpdev->driver_override = "rpmsg_ns";
>> +	rpdev->src = RPMSG_NS_ADDR;
>> +	rpdev->dst = RPMSG_NS_ADDR;
>> +
>> +	return rpmsg_register_device(rpdev);
>> +}
>> +
>>  #endif
>> diff --git a/drivers/rpmsg/rpmsg_ns.c b/drivers/rpmsg/rpmsg_ns.c
>> new file mode 100644
>> index 000000000000..3c929b6976a6
>> --- /dev/null
>> +++ b/drivers/rpmsg/rpmsg_ns.c
>> @@ -0,0 +1,135 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright (C) STMicroelectronics 2020 - All Rights Reserved
>> + */
>> +#include <linux/device.h>
>> +#include <linux/kernel.h>
>> +#include <linux/module.h>
>> +#include <linux/slab.h>
>> +#include "rpmsg_internal.h"
>> +
>> +/**
>> + * enum rpmsg_ns_flags - dynamic name service announcement flags
>> + *
>> + * @RPMSG_NS_CREATE: a new remote service was just created
>> + * @RPMSG_NS_DESTROY: a known remote service was just destroyed
>> + */
>> +enum rpmsg_ns_flags {
>> +	RPMSG_NS_CREATE		= 0,
>> +	RPMSG_NS_DESTROY	= 1,
>> +};
>> +
>> +/**
>> + * struct rpmsg_ns_msg - dynamic name service announcement message
>> + * @name: name of remote service that is published
>> + * @addr: address of remote service that is published
>> + * @flags: indicates whether service is created or destroyed
>> + *
>> + * This message is sent across to publish a new service, or announce
>> + * about its removal. When we receive these messages, an appropriate
>> + * rpmsg channel (i.e device) is created/destroyed. In turn, the ->probe()
>> + * or ->remove() handler of the appropriate rpmsg driver will be invoked
>> + * (if/as-soon-as one is registered).
>> + */
>> +struct rpmsg_ns_msg {
>> +	char name[RPMSG_NAME_SIZE];
>> +	__le32 addr;
>> +	__le32 flags;
>> +} __packed;
>> +
>> +/* Invoked when a name service announcement arrives */
>> +static int rpmsg_ns_cb(struct rpmsg_device *rpdev, void *data, int len,
>> +		       void *priv, u32 src)
>> +{
>> +	struct rpmsg_ns_msg *msg = data;
>> +	struct rpmsg_device *newch;
>> +	struct rpmsg_channel_info chinfo;
>> +	struct device *dev = &rpdev->dev;
>> +	unsigned int flags = le32_to_cpu(msg->flags);
>> +	int ret;
>> +
>> +#if defined(CONFIG_DYNAMIC_DEBUG)
>> +	dynamic_hex_dump("NS announcement: ", DUMP_PREFIX_NONE, 16, 1,
>> +			 data, len, true);
>> +#endif
>> +
>> +	if (len != sizeof(*msg)) {
>> +		dev_err(dev, "malformed ns msg (%d)\n", len);
>> +		return -EINVAL;
>> +	}
>> +
>> +	/* Don't trust the remote processor for null terminating the name */
>> +	msg->name[RPMSG_NAME_SIZE - 1] = '\0';
>> +
>> +	strncpy(chinfo.name, msg->name, sizeof(chinfo.name));
>> +	chinfo.src = RPMSG_ADDR_ANY;
>> +	chinfo.dst = le32_to_cpu(msg->addr);
> 
> As I said in an earlier comment I would like to avoid redefining structures that
> already exist.  With this patch [1] we made structure rpmsg_hdr and rpmsg_ns_msg
> virtIO specific, which in hindsight, wasn't the best move forward.  After taking
> another look at this set and keeping Guennadi's work in mind it is probably best
> to keep rpmsg_hdr and rpmsg_ns_msg generic and do the byte conversion based on
> the transport layer used by the rpmsg_device.  Taking the above as an example we
> would have:
> 
>         chinfo.dst = rpmsg32_to_cpu(rpdev, msg->addr);
> 
> Where rpmsg32_to_cpu() would be defined as follow:
> 
> u32 rpmsg32_to_cpu(struct rpmsg_device *rpdev, u32 val)
> {
>         return rpdev->ops->transport32_to_cpu(rpdev, val); 
> }
> 
> And in the case of a virtIO based rpmsg_device like we currently have:
> 
> u32 virtio_transport32_to_cpu(struct rpmsg_device *rpdev, u32 val)
> {
>         struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
>         struct virtproc_info *vrp = vch->vrp;
> 
>         return virtio32_to_cpu(vrp->vdev, val);
> }
> 
> That would allow the virtualization people (and anyone else) to use the RPMSG
> common code without modification and split up RPMSG name service from the
> transport layer, as you're doing in this patch.

This looks to me an excellent idea! More flexible than patch [1].

I'm just wondering if it wouldn't be useful to extend API to 16 and 64 bits for
future evolutions.

> 
> We need to fix the current code before moving further with either
> patchset (yours and Guennadi's).  I started working on a patchset that does that
> but I'll need to merge it with yours on Monday (I'm out of time for today).

That makes sense.

Thanks,
Arnaud

> 
> Thanks,
> Mathieu 
> 
> [1]. 111d1089700c rpmsg: virtio: add endianness conversions
> 
>> +
>> +	dev_info(dev, "%sing channel %s addr 0x%x\n",
>> +		 (flags & RPMSG_NS_DESTROY) ? "destroy" : "creat",
>> +		 msg->name, chinfo.dst);
>> +
>> +	if (flags & RPMSG_NS_DESTROY) {
>> +		ret = rpmsg_release_channel(rpdev, &chinfo);
>> +		if (ret)
>> +			dev_err(dev, "rpmsg_destroy_channel failed: %d\n", ret);
>> +	} else {
>> +		newch = rpmsg_create_channel(rpdev, &chinfo);
>> +		if (!newch)
>> +			dev_err(dev, "rpmsg_create_channel failed\n");
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static int rpmsg_ns_probe(struct rpmsg_device *rpdev)
>> +{
>> +	struct rpmsg_channel_info ns_chinfo;
>> +	struct rpmsg_endpoint *ns_ept;
>> +
>> +	ns_chinfo.src = RPMSG_NS_ADDR;
>> +	ns_chinfo.dst = RPMSG_NS_ADDR;
>> +	strcpy(ns_chinfo.name, "name_service");
>> +
>> +	/*
>> +	 * Create the NS announcement service endpoint associated to the RPMsg
>> +	 * device. The endpoint will be automatically destroyed when the RPMsg
>> +	 * device will be deleted.
>> +	 */
>> +	ns_ept = rpmsg_create_ept(rpdev, rpmsg_ns_cb, NULL, ns_chinfo);
>> +	if (!ns_ept) {
>> +		dev_err(&rpdev->dev, "failed to create the ns ept\n");
>> +		return -ENOMEM;
>> +	}
>> +	rpdev->ept = ns_ept;
>> +
>> +	return 0;
>> +}
>> +
>> +static struct rpmsg_driver rpmsg_ns_driver = {
>> +	.drv.name = "rpmsg_ns",
>> +	.probe = rpmsg_ns_probe,
>> +};
>> +
>> +static int rpmsg_ns_init(void)
>> +{
>> +	int ret;
>> +
>> +	ret = register_rpmsg_driver(&rpmsg_ns_driver);
>> +	if (ret < 0)
>> +		pr_err("%s: Failed to register rpmsg driver\n", __func__);
>> +
>> +	return ret;
>> +}
>> +postcore_initcall(rpmsg_ns_init);
>> +
>> +static void rpmsg_ns_exit(void)
>> +{
>> +	unregister_rpmsg_driver(&rpmsg_ns_driver);
>> +}
>> +module_exit(rpmsg_ns_exit);
>> +
>> +MODULE_DESCRIPTION("Name service announcement rpmsg Driver");
>> +MODULE_AUTHOR("Arnaud Pouliquen <arnaud.pouliquen@xxxxxx>");
>> +MODULE_ALIAS("rpmsg_ns");
>> +MODULE_LICENSE("GPL v2");
>> -- 
>> 2.17.1
>>