Messages in this thread | | | Subject | Re: [PATCH i2c/slave-mqueue v1] i2c: slave-mqueue: add a slave backend to receive and queue messages | From | "Wang, Haiyue" <> | Date | Tue, 20 Mar 2018 09:44:14 +0800 |
| |
Thanks, Andy.
Hi Wolfram,
Let me introduce some development background, it is used for OpenBMC project,
which belongs to the Linux Foundation now (https://www.linuxfoundation.org/blog/openbmc-project-community-comes-together-at-the-linux-foundation-to-define-open-source-implementation-of-bmc-firmware-stack/).
1. *https://goo.gl/WgvPFi*
*** <https://goo.gl/WgvPFi>***https://lists.ozlabs.org/pipermail/openbmc/2018-January/010493.html* <https://goo.gl/WgvPFi>*
**
*IPMI is embedded within IPMB (similar to KCS, BT?)*
*
*
Who started, who responded to messages
*
We need a kernel interface for handling a multi-master slave
*
Dell has a non-standard i2c IPMB interface
o
Kernel maintains table of outstanding commands
*
Brendan suggests we need a kernel driver for doing both MCTP and IPMB
*
We can’t do them both in usersland as MCTP makes extensions to SMBUS in order to allow arbitration. Problematic extension is the “MCTP fairness arbitration”. Requires the i2c controllers on the bus (masters/slaves) to observe the line for a certain period of time in order to see who is using the line. There’s no userspace API for this, and it the timing requirements are tight
*
Slave mode is not yet exposed to the user
*
As we don’t have a userspace interface, it makes sense to add a new one
*
BR, Haiyue
On 2018-03-20 03:32, Andy Shevchenko wrote: > On Sat, 2018-03-17 at 11:48 +0800, Haiyue Wang wrote: >> Some protocols over I2C are designed for bi-directional transferring >> messages by using I2C Master Write protocol. Like the MCTP (Management >> Component Transport Protocol) and IPMB (Intelligent Platform >> Management >> Bus), they both require that the userspace can receive messages from >> I2C dirvers under slave mode. >> >> This new slave mqueue backend is used to receive and queue messages, >> it >> will exposes these messages to userspace by sysfs bin file. >> > Wolfram, I'm not sure this is the best approach, though I can't propose > anything else right now. > > If you are satisfied with it, I give a formal > > Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> > >> Signed-off-by: Haiyue Wang <haiyue.wang@linux.intel.com> >> --- >> Documentation/i2c/slave-mqueue-backend.rst | 125 ++++++++++++++++++ >> drivers/i2c/Kconfig | 13 ++ >> drivers/i2c/Makefile | 1 + >> drivers/i2c/i2c-slave-mqueue.c | 202 >> +++++++++++++++++++++++++++++ >> 4 files changed, 341 insertions(+) >> create mode 100644 Documentation/i2c/slave-mqueue-backend.rst >> create mode 100644 drivers/i2c/i2c-slave-mqueue.c >> >> diff --git a/Documentation/i2c/slave-mqueue-backend.rst >> b/Documentation/i2c/slave-mqueue-backend.rst >> new file mode 100644 >> index 0000000..69d6437 >> --- /dev/null >> +++ b/Documentation/i2c/slave-mqueue-backend.rst >> @@ -0,0 +1,125 @@ >> +.. SPDX-License-Identifier: GPL-2.0 >> + >> +===================================== >> +Linux I2C slave message queue backend >> +===================================== >> + >> +:Author: Haiyue Wang <haiyue.wang@linux.intel.com> >> + >> +Some protocols over I2C/SMBus are designed for bi-directional >> transferring >> +messages by using I2C Master Write protocol. This requires that both >> sides >> +of the communication have slave addresses. >> + >> +Like MCTP (Management Component Transport Protocol) and IPMB >> (Intelligent >> +Platform Management Bus), they both require that the userspace can >> receive >> +messages from i2c dirvers under slave mode. >> + >> +This I2C slave mqueue (message queue) backend is used to receive and >> queue >> +messages from the remote i2c intelligent device; and it will add the >> target >> +slave address (with R/W# bit is always 0) into the message at the >> first byte, >> +so that userspace can use this byte to dispatch the messages into >> different >> +handling modules. Also, like IPMB, the address byte is in its message >> format, >> +it needs it to do checksum. >> + >> +For messages are time related, so this backend will flush the oldest >> message >> +to queue the newest one. >> + >> +Link >> +---- >> +`Intelligent Platform Management Bus >> +Communications Protocol Specification >> +<https://www.intel.com/content/dam/www/public/us/en/documents/product >> -briefs/ipmp-spec-v1.0.pdf>`_ >> + >> +`Management Component Transport Protocol (MCTP) >> +SMBus/I2C Transport Binding Specification >> +<https://www.dmtf.org/sites/default/files/standards/documents/DSP0237 >> _1.1.0.pdf>`_ >> + >> +How to use >> +---------- >> +For example, the I2C5 bus has slave address 0x10, bellowing command >> will create >> +the related message queue interface: >> + >> + echo slave-mqueue 0x1010 > /sys/bus/i2c/devices/i2c-5/new_device >> + >> +Then you can dump the messages like this: >> + >> + hexdump -C /sys/bus/i2c/devices/5-1010/slave-mqueue >> + >> +Code Example >> +------------ >> +*Note: call 'lseek' before 'read', this is a requirement from kernfs' >> design.* >> + >> +:: >> + >> + #include <sys/types.h> >> + #include <sys/stat.h> >> + #include <unistd.h> >> + #include <poll.h> >> + #include <time.h> >> + #include <fcntl.h> >> + #include <stdio.h> >> + >> + int main(int argc, char *argv[]) >> + { >> + int i, r; >> + struct pollfd pfd; >> + struct timespec ts; >> + unsigned char data[256]; >> + >> + pfd.fd = open(argv[1], O_RDONLY | O_NONBLOCK); >> + if (pfd.fd < 0) >> + return -1; >> + >> + pfd.events = POLLPRI; >> + >> + while (1) { >> + r = poll(&pfd, 1, 5000); >> + >> + if (r < 0) >> + break; >> + >> + if (r == 0 || !(pfd.revents & POLLPRI)) >> + continue; >> + >> + lseek(pfd.fd, 0, SEEK_SET); >> + r = read(pfd.fd, data, sizeof(data)); >> + if (r <= 0) >> + continue; >> + >> + clock_gettime(CLOCK_MONOTONIC, &ts); >> + printf("[%ld.%.9ld] :", ts.tv_sec, ts.tv_nsec); >> + for (i = 0; i < r; i++) >> + printf(" %02x", data[i]); >> + printf("\n"); >> + } >> + >> + close(pfd.fd); >> + >> + return 0; >> + } >> + >> +Result >> +------ >> +*./a.out "/sys/bus/i2c/devices/5-1010/slave-mqueue"* >> + >> +:: >> + >> + [10183.232500449] : 20 18 c8 2c 78 01 5b >> + [10183.479358348] : 20 18 c8 2c 78 01 5b >> + [10183.726556812] : 20 18 c8 2c 78 01 5b >> + [10183.972605863] : 20 18 c8 2c 78 01 5b >> + [10184.220124772] : 20 18 c8 2c 78 01 5b >> + [10184.467764166] : 20 18 c8 2c 78 01 5b >> + [10193.233421784] : 20 18 c8 2c 7c 01 57 >> + [10193.480273460] : 20 18 c8 2c 7c 01 57 >> + [10193.726788733] : 20 18 c8 2c 7c 01 57 >> + [10193.972781945] : 20 18 c8 2c 7c 01 57 >> + [10194.220487360] : 20 18 c8 2c 7c 01 57 >> + [10194.468089259] : 20 18 c8 2c 7c 01 57 >> + [10203.233433099] : 20 18 c8 2c 80 01 53 >> + [10203.481058715] : 20 18 c8 2c 80 01 53 >> + [10203.727610472] : 20 18 c8 2c 80 01 53 >> + [10203.974044856] : 20 18 c8 2c 80 01 53 >> + [10204.220734634] : 20 18 c8 2c 80 01 53 >> + [10204.468461664] : 20 18 c8 2c 80 01 53 >> + >> diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig >> index efc3354..7053b5b 100644 >> --- a/drivers/i2c/Kconfig >> +++ b/drivers/i2c/Kconfig >> @@ -118,6 +118,19 @@ if I2C_SLAVE >> config I2C_SLAVE_EEPROM >> tristate "I2C eeprom slave driver" >> >> +config I2C_SLAVE_MQUEUE >> + tristate "I2C mqueue (message queue) slave driver" >> + help >> + Some protocols over I2C are designed for bi-directional >> transferring >> + messages by using I2C Master Write protocol. This driver is >> used to >> + receive and queue messages from the remote I2C device. >> + >> + Userspace can get the messages by reading sysfs file that >> this driver >> + exposes. >> + >> + This support is also available as a module. If so, the >> module will be >> + called i2c-slave-mqueue. >> + >> endif >> >> config I2C_DEBUG_CORE >> diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile >> index 72c94c6..7ec287b 100644 >> --- a/drivers/i2c/Makefile >> +++ b/drivers/i2c/Makefile >> @@ -16,6 +16,7 @@ obj-$(CONFIG_I2C_MUX) += i2c-mux.o >> obj-y += algos/ busses/ muxes/ >> obj-$(CONFIG_I2C_STUB) += i2c-stub.o >> obj-$(CONFIG_I2C_SLAVE_EEPROM) += i2c-slave-eeprom.o >> +obj-$(CONFIG_I2C_SLAVE_MQUEUE) += i2c-slave-mqueue.o >> >> ccflags-$(CONFIG_I2C_DEBUG_CORE) := -DDEBUG >> CFLAGS_i2c-core-base.o := -Wno-deprecated-declarations >> diff --git a/drivers/i2c/i2c-slave-mqueue.c b/drivers/i2c/i2c-slave- >> mqueue.c >> new file mode 100644 >> index 0000000..a486e85 >> --- /dev/null >> +++ b/drivers/i2c/i2c-slave-mqueue.c >> @@ -0,0 +1,202 @@ >> +// SPDX-License-Identifier: GPL-2.0 >> +// Copyright (c) 2017 - 2018, Intel Corporation. >> + >> +#include <linux/i2c.h> >> +#include <linux/kernel.h> >> +#include <linux/module.h> >> +#include <linux/of.h> >> +#include <linux/slab.h> >> +#include <linux/spinlock.h> >> +#include <linux/sysfs.h> >> + >> +#define MQ_MSGBUF_SIZE 128 >> +#define MQ_QUEUE_SIZE 32 >> +#define MQ_QUEUE_NEXT(x) (((x) + 1) & (MQ_QUEUE_SIZE - 1)) >> + >> +struct mq_msg { >> + int len; >> + u8 *buf; >> +}; >> + >> +struct mq_queue { >> + struct bin_attribute bin; >> + struct kernfs_node *kn; >> + >> + spinlock_t lock; /* spinlock for queue index >> handling */ >> + int in; >> + int out; >> + >> + struct mq_msg *curr; >> + int truncated; /* drop current if >> truncated */ >> + struct mq_msg queue[MQ_QUEUE_SIZE]; >> +}; >> + >> +static int i2c_slave_mqueue_callback(struct i2c_client *client, >> + enum i2c_slave_event event, u8 >> *val) >> +{ >> + struct mq_queue *mq = i2c_get_clientdata(client); >> + struct mq_msg *msg = mq->curr; >> + int ret = 0; >> + >> + switch (event) { >> + case I2C_SLAVE_WRITE_REQUESTED: >> + mq->truncated = 0; >> + >> + msg->len = 1; >> + msg->buf[0] = client->addr << 1; >> + break; >> + >> + case I2C_SLAVE_WRITE_RECEIVED: >> + if (msg->len < MQ_MSGBUF_SIZE) { >> + msg->buf[msg->len++] = *val; >> + } else { >> + dev_err(&client->dev, "message is >> truncated!\n"); >> + mq->truncated = 1; >> + ret = -EINVAL; >> + } >> + break; >> + >> + case I2C_SLAVE_STOP: >> + if (unlikely(mq->truncated)) >> + break; >> + >> + spin_lock(&mq->lock); >> + mq->in = MQ_QUEUE_NEXT(mq->in); >> + mq->curr = &mq->queue[mq->in]; >> + >> + /* Flush the oldest message */ >> + if (mq->out == mq->in) >> + mq->out = MQ_QUEUE_NEXT(mq->out); >> + spin_unlock(&mq->lock); >> + >> + kernfs_notify(mq->kn); >> + break; >> + >> + default: >> + *val = 0xFF; >> + break; >> + } >> + >> + return ret; >> +} >> + >> +static ssize_t i2c_slave_mqueue_bin_read(struct file *filp, >> + struct kobject *kobj, >> + struct bin_attribute *attr, >> + char *buf, loff_t pos, >> size_t count) >> +{ >> + struct mq_queue *mq; >> + struct mq_msg *msg; >> + unsigned long flags; >> + bool more = false; >> + ssize_t ret = 0; >> + >> + mq = dev_get_drvdata(container_of(kobj, struct device, >> kobj)); >> + >> + spin_lock_irqsave(&mq->lock, flags); >> + if (mq->out != mq->in) { >> + msg = &mq->queue[mq->out]; >> + >> + if (msg->len <= count) { >> + ret = msg->len; >> + memcpy(buf, msg->buf, ret); >> + } else { >> + ret = -EOVERFLOW; /* Drop this HUGE one. */ >> + } >> + >> + mq->out = MQ_QUEUE_NEXT(mq->out); >> + if (mq->out != mq->in) >> + more = true; >> + } >> + spin_unlock_irqrestore(&mq->lock, flags); >> + >> + if (more) >> + kernfs_notify(mq->kn); >> + >> + return ret; >> +} >> + >> +static int i2c_slave_mqueue_probe(struct i2c_client *client, >> + const struct i2c_device_id *id) >> +{ >> + struct device *dev = &client->dev; >> + struct mq_queue *mq; >> + int ret, i; >> + void *buf; >> + >> + mq = devm_kzalloc(dev, sizeof(*mq), GFP_KERNEL); >> + if (!mq) >> + return -ENOMEM; >> + >> + BUILD_BUG_ON(!is_power_of_2(MQ_QUEUE_SIZE)); >> + >> + buf = devm_kmalloc_array(dev, MQ_QUEUE_SIZE, MQ_MSGBUF_SIZE, >> + GFP_KERNEL); >> + if (!buf) >> + return -ENOMEM; >> + >> + for (i = 0; i < MQ_QUEUE_SIZE; i++) >> + mq->queue[i].buf = buf + i * MQ_MSGBUF_SIZE; >> + >> + i2c_set_clientdata(client, mq); >> + >> + spin_lock_init(&mq->lock); >> + mq->curr = &mq->queue[0]; >> + >> + sysfs_bin_attr_init(&mq->bin); >> + mq->bin.attr.name = "slave-mqueue"; >> + mq->bin.attr.mode = 0400; >> + mq->bin.read = i2c_slave_mqueue_bin_read; >> + mq->bin.size = MQ_MSGBUF_SIZE * MQ_QUEUE_SIZE; >> + >> + ret = sysfs_create_bin_file(&dev->kobj, &mq->bin); >> + if (ret) >> + return ret; >> + >> + mq->kn = kernfs_find_and_get(dev->kobj.sd, mq- >>> bin.attr.name); >> + if (!mq->kn) { >> + sysfs_remove_bin_file(&dev->kobj, &mq->bin); >> + return -EFAULT; >> + } >> + >> + ret = i2c_slave_register(client, i2c_slave_mqueue_callback); >> + if (ret) { >> + kernfs_put(mq->kn); >> + sysfs_remove_bin_file(&dev->kobj, &mq->bin); >> + return ret; >> + } >> + >> + return 0; >> +}; >> + >> +static int i2c_slave_mqueue_remove(struct i2c_client *client) >> +{ >> + struct mq_queue *mq = i2c_get_clientdata(client); >> + >> + i2c_slave_unregister(client); >> + >> + kernfs_put(mq->kn); >> + sysfs_remove_bin_file(&client->dev.kobj, &mq->bin); >> + >> + return 0; >> +} >> + >> +static const struct i2c_device_id i2c_slave_mqueue_id[] = { >> + { "slave-mqueue", 0 }, >> + { } >> +}; >> +MODULE_DEVICE_TABLE(i2c, i2c_slave_mqueue_id); >> + >> +static struct i2c_driver i2c_slave_mqueue_driver = { >> + .driver = { >> + .name = "i2c-slave-mqueue", >> + }, >> + .probe = i2c_slave_mqueue_probe, >> + .remove = i2c_slave_mqueue_remove, >> + .id_table = i2c_slave_mqueue_id, >> +}; >> +module_i2c_driver(i2c_slave_mqueue_driver); >> + >> +MODULE_LICENSE("GPL v2"); >> +MODULE_AUTHOR("Haiyue Wang <haiyue.wang@linux.intel.com>"); >> +MODULE_DESCRIPTION("I2C slave mode for receiving and queuing >> messages");
| |