Hey, On Fri, May 24, 2019 at 10:43:16AM +0800, Wang, Haiyue wrote: > Thanks for interest, the design idea is from: > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/i2c/i2c-slave-eeprom.c?h=v5.2-rc1 > > and > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/i2c/slave-interface > > Then you will get the answer. ;-) Well, maybe :-) see further comments inline.. > > BR, > > Haiyue > > > 在 2019-05-24 06:03, Eduardo Valentin 写道: > >Hey Wang, > > > >On Tue, Apr 24, 2018 at 01:06:32AM +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. > >> > >>Signed-off-by: Haiyue Wang <haiyue.wang@xxxxxxxxxxxxxxx> > >>--- > >>v4 -> v5: > >> - Typo: bellowing -> the below > >> > >>v3 -> v4: > >> - Drop the small message after receiving I2C STOP. > >> > >>v2 -> v3: > >> - Just remove the ';' after the end '}' of i2c_slave_mqueue_probe(). > >> > >>v1 -> v2: > >> - Change MQ_MSGBUF_SIZE and MQ_QUEUE_SIZE to be configurable by Kconfig. > >>--- > >> Documentation/i2c/slave-mqueue-backend.rst | 125 ++++++++++++++++++ > >> drivers/i2c/Kconfig | 25 ++++ > >> drivers/i2c/Makefile | 1 + > >> drivers/i2c/i2c-slave-mqueue.c | 203 +++++++++++++++++++++++++++++ > >> 4 files changed, 354 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..3966cf0 > >>--- /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@xxxxxxxxxxxxxxx> > >>+ > >>+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, the below 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..31e57d2 100644 > >>--- a/drivers/i2c/Kconfig > >>+++ b/drivers/i2c/Kconfig > >>@@ -118,6 +118,31 @@ if I2C_SLAVE > >> config I2C_SLAVE_EEPROM > >> tristate "I2C eeprom slave driver" > >>+config I2C_SLAVE_MQUEUE_MESSAGE_SIZE > >>+ int "The message size of I2C mqueue slave" > >>+ default 120 > >>+ > >>+config I2C_SLAVE_MQUEUE_QUEUE_SIZE > >>+ int "The queue size of I2C mqueue slave" > >>+ default 32 > >>+ help > >>+ This number MUST be power of 2. > >>+ > >>+config I2C_SLAVE_MQUEUE > >>+ tristate "I2C mqueue (message queue) slave driver" > >>+ select I2C_SLAVE_MQUEUE_MESSAGE_SIZE > >>+ select I2C_SLAVE_MQUEUE_QUEUE_SIZE > >>+ 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..424f435 > >>--- /dev/null > >>+++ b/drivers/i2c/i2c-slave-mqueue.c > >>@@ -0,0 +1,203 @@ > >>+// 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 CONFIG_I2C_SLAVE_MQUEUE_MESSAGE_SIZE > >>+#define MQ_QUEUE_SIZE CONFIG_I2C_SLAVE_MQUEUE_QUEUE_SIZE > >>+#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 */ > >I wonder why you decided to lock only in/out accesses and not the mq_queue struct. > > > >>+ 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; > >Do we need to lock the accesses to msg->buf? how about to msg->len? this code goes access and modify data here, e.g. msg->len and msg->buf. On this case (I2C_SLAVE_WRITE_RECEIVED), this code wont protect access. This can cause concurrence issues if you receive an IRQ when the user is on your bin_read(). > > > >>+ } else { > >>+ dev_err(&client->dev, "message is truncated!\n"); > >>+ mq->truncated = 1; > >>+ ret = -EINVAL; > >>+ } > >>+ break; > >>+ > >>+ case I2C_SLAVE_STOP: > >>+ if (unlikely(mq->truncated || msg->len < 2)) > >>+ break; > >>+ > >>+ spin_lock(&mq->lock); > >>+ mq->in = MQ_QUEUE_NEXT(mq->in); > >>+ mq->curr = &mq->queue[mq->in]; > >>+ mq->curr->len = 0; > >>+ > >>+ /* Flush the oldest message */ > >>+ if (mq->out == mq->in) > >>+ mq->out = MQ_QUEUE_NEXT(mq->out); > >>+ spin_unlock(&mq->lock); > >>+ Here you protect most of it, but you still access msg->len for read.. with no protection. > >>+ 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); > >Is buf a userspace pointer? should it be a copy_to_user() here? > > > >>+ } 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@xxxxxxxxxxxxxxx>"); > >>+MODULE_DESCRIPTION("I2C slave mode for receiving and queuing messages"); > >>-- > >>2.7.4 > >> -- All the best, Eduardo Valentin
