[PATCH rtems] i2c: Add non blocking read / write
Christian Mauderer
christian.mauderer at embedded-brains.de
Wed May 26 14:39:47 UTC 2021
This adds the possibility to open an I2C bus with O_NONBLOCK (or set it
later via fcntl) to get non-blocking transmissions. This means that if
the bus is busy, a read, write or transfer ioctl will return with a
EAGAIN errno.
---
NOTE: This patch needs
https://lists.rtems.org/pipermail/devel/2021-May/067462.html applied too.
cpukit/dev/i2c/i2c-bus.c | 45 ++++++++++--
cpukit/include/dev/i2c/i2c.h | 44 ++++++++++-
testsuites/libtests/i2c01/init.c | 121 ++++++++++++++++++++++++++++++-
3 files changed, 203 insertions(+), 7 deletions(-)
diff --git a/cpukit/dev/i2c/i2c-bus.c b/cpukit/dev/i2c/i2c-bus.c
index 472222c4ab..618a817b1a 100644
--- a/cpukit/dev/i2c/i2c-bus.c
+++ b/cpukit/dev/i2c/i2c-bus.c
@@ -31,6 +31,11 @@
#include <stdlib.h>
#include <string.h>
+int i2c_bus_try_obtain(i2c_bus *bus)
+{
+ return rtems_recursive_mutex_try_lock(&bus->mutex);
+}
+
void i2c_bus_obtain(i2c_bus *bus)
{
rtems_recursive_mutex_lock(&bus->mutex);
@@ -41,7 +46,12 @@ void i2c_bus_release(i2c_bus *bus)
rtems_recursive_mutex_unlock(&bus->mutex);
}
-int i2c_bus_transfer(i2c_bus *bus, i2c_msg *msgs, uint32_t msg_count)
+int i2c_bus_do_transfer(
+ i2c_bus *bus,
+ i2c_msg *msgs,
+ uint32_t msg_count,
+ uint32_t flags
+)
{
int err;
uint32_t i;
@@ -63,13 +73,24 @@ int i2c_bus_transfer(i2c_bus *bus, i2c_msg *msgs, uint32_t msg_count)
}
}
- i2c_bus_obtain(bus);
+ if ((flags & I2C_BUS_NOBLOCK) != 0) {
+ if (i2c_bus_try_obtain(bus) != 0) {
+ return -EAGAIN;
+ }
+ } else {
+ i2c_bus_obtain(bus);
+ }
err = (*bus->transfer)(bus, msgs, msg_count);
i2c_bus_release(bus);
return err;
}
+int i2c_bus_transfer(i2c_bus *bus, i2c_msg *msgs, uint32_t msg_count)
+{
+ return i2c_bus_do_transfer(bus, msgs, msg_count, 0);
+}
+
static ssize_t i2c_bus_read(
rtems_libio_t *iop,
void *buffer,
@@ -84,12 +105,17 @@ static ssize_t i2c_bus_read(
.buf = buffer
};
int err;
+ unsigned flags = 0;
if (bus->ten_bit_address) {
msg.flags |= I2C_M_TEN;
}
- err = i2c_bus_transfer(bus, &msg, 1);
+ if (rtems_libio_iop_is_no_delay(iop)) {
+ flags |= I2C_BUS_NOBLOCK;
+ }
+
+ err = i2c_bus_do_transfer(bus, &msg, 1, flags);
if (err == 0) {
return msg.len;
} else {
@@ -111,12 +137,17 @@ static ssize_t i2c_bus_write(
.buf = RTEMS_DECONST(void *, buffer)
};
int err;
+ unsigned flags = 0;
if (bus->ten_bit_address) {
msg.flags |= I2C_M_TEN;
}
- err = i2c_bus_transfer(bus, &msg, 1);
+ if (rtems_libio_iop_is_no_delay(iop)) {
+ flags |= I2C_BUS_NOBLOCK;
+ }
+
+ err = i2c_bus_do_transfer(bus, &msg, 1, flags);
if (err == 0) {
return msg.len;
} else {
@@ -133,12 +164,16 @@ static int i2c_bus_ioctl(
i2c_bus *bus = IMFS_generic_get_context_by_iop(iop);
i2c_rdwr_ioctl_data *rdwr;
int err;
+ unsigned flags = 0;
switch (command) {
case I2C_RDWR:
rdwr = arg;
if (rdwr->nmsgs > 0) {
- err = i2c_bus_transfer(bus, rdwr->msgs, rdwr->nmsgs);
+ if (rtems_libio_iop_is_no_delay(iop)) {
+ flags |= I2C_BUS_NOBLOCK;
+ }
+ err = i2c_bus_do_transfer(bus, rdwr->msgs, rdwr->nmsgs, flags);
} else {
err = 0;
}
diff --git a/cpukit/include/dev/i2c/i2c.h b/cpukit/include/dev/i2c/i2c.h
index ac2c369785..5aa45e390c 100644
--- a/cpukit/include/dev/i2c/i2c.h
+++ b/cpukit/include/dev/i2c/i2c.h
@@ -242,6 +242,16 @@ int i2c_bus_register(
const char *bus_path
);
+/**
+ * @brief Try to obtain the bus.
+ *
+ * @param[in] bus The bus control.
+ *
+ * @retval 0 Successful operation.
+ * @retval EBUSY if mutex is already locked.
+ */
+int i2c_bus_try_obtain(i2c_bus *bus);
+
/**
* @brief Obtains the bus.
*
@@ -259,7 +269,8 @@ void i2c_bus_release(i2c_bus *bus);
/**
* @brief Transfers I2C messages.
*
- * The bus is obtained before the transfer and released afterwards.
+ * The bus is obtained before the transfer and released afterwards. This is the
+ * same like calling @ref i2c_bus_do_transfer with flags set to 0.
*
* @param[in] bus The bus control.
* @param[in] msgs The messages to transfer.
@@ -271,6 +282,37 @@ void i2c_bus_release(i2c_bus *bus);
*/
int i2c_bus_transfer(i2c_bus *bus, i2c_msg *msgs, uint32_t msg_count);
+/**
+ * @brief Transfers I2C messages with optional flags.
+ *
+ * The bus is obtained before the transfer and released afterwards. If the flag
+ * I2C_BUS_NOBLOCK is set and the bus is already obtained, nothing will be
+ * transfered and the function returns with an -EAGAIN.
+ *
+ * @param[in] bus The bus control.
+ * @param[in] msgs The messages to transfer.
+ * @param[in] msg_count The count of messages to transfer. It must be
+ * positive.
+ * @param[in] flags Options for the whole transfer.
+ *
+ * @retval 0 Successful operation.
+ * @retval -EAGAIN if @ref I2C_BUS_NOBLOCK is set and the bus is already
+ * obtained.
+ * @retval negative Negative error number in case of an error.
+ */
+int i2c_bus_do_transfer(
+ i2c_bus *bus,
+ i2c_msg *msgs,
+ uint32_t msg_count,
+ uint32_t flags
+);
+
+/**
+ * @brief I2C bus transfer flag to indicate that the task should not block if
+ * the bus is busy on a new transfer.
+ */
+#define I2C_BUS_NOBLOCK (1u << 0)
+
/** @} */
/**
diff --git a/testsuites/libtests/i2c01/init.c b/testsuites/libtests/i2c01/init.c
index 83027ed548..c71b78c275 100644
--- a/testsuites/libtests/i2c01/init.c
+++ b/testsuites/libtests/i2c01/init.c
@@ -336,6 +336,124 @@ static void test_simple_read_write(test_bus *bus, int fd)
rtems_test_assert(memcmp(&buf[0], &abc[0], sizeof(buf)) == 0);
}
+typedef struct {
+ rtems_id caller;
+ int fd;
+} bus_obtainer_ctx;
+
+static void bus_obtainer_task(rtems_task_argument arg)
+{
+ rtems_event_set e = 0;
+ bus_obtainer_ctx *c = (bus_obtainer_ctx *) arg;
+ int rv;
+ rtems_status_code sc;
+
+ rv = ioctl(c->fd, I2C_BUS_OBTAIN);
+ rtems_test_assert(rv == 0);
+
+ sc = rtems_event_send(c->caller, RTEMS_EVENT_1);
+ rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+ sc = rtems_event_receive(
+ RTEMS_EVENT_1,
+ RTEMS_EVENT_ANY | RTEMS_WAIT,
+ 100,
+ &e
+ );
+ rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
+ rv = ioctl(c->fd, I2C_BUS_RELEASE);
+ rtems_test_assert(rv == 0);
+
+ sc = rtems_event_send(c->caller, RTEMS_EVENT_1);
+ rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+}
+
+static void test_nonblock_read_write(test_bus *bus, int fd)
+{
+ int flags;
+ int rv;
+ char buf[3];
+ ssize_t n;
+ i2c_msg msgs[] = {{
+ .addr = 1,
+ .flags = I2C_M_STOP,
+ .len = sizeof(buf),
+ .buf = (uint8_t *) buf,
+ }};
+ struct i2c_rdwr_ioctl_data payload = {
+ .msgs = msgs,
+ .nmsgs = sizeof(msgs)/sizeof(msgs[0]),
+ };
+ rtems_id id;
+ rtems_event_set e = 0;
+ bus_obtainer_ctx ctx = {
+ .caller = rtems_task_self(),
+ .fd = fd,
+ };
+ rtems_status_code sc;
+
+ flags = fcntl(fd, F_GETFL, 0);
+ rtems_test_assert(flags > 0);
+
+ rv = fcntl(fd, F_SETFL, flags | O_NONBLOCK);
+ rtems_test_assert(rv != -1);
+
+ sc = rtems_task_create(
+ rtems_build_name('O', 'B', 'T', 'A'),
+ 2,
+ RTEMS_MINIMUM_STACK_SIZE,
+ RTEMS_DEFAULT_MODES,
+ RTEMS_DEFAULT_ATTRIBUTES,
+ &id
+ );
+ rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
+ sc = rtems_task_start(
+ id,
+ bus_obtainer_task,
+ (rtems_task_argument) &ctx
+ );
+ rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
+ sc = rtems_event_receive(
+ RTEMS_EVENT_1,
+ RTEMS_EVENT_ANY | RTEMS_WAIT,
+ 100,
+ &e
+ );
+ rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
+ errno = 0;
+ n = read(fd, &buf[0], sizeof(buf));
+ rtems_test_assert(n == -1);
+ rtems_test_assert(errno == EAGAIN);
+
+ errno = 0;
+ n = write(fd, &buf[0], sizeof(buf));
+ rtems_test_assert(n == -1);
+ rtems_test_assert(errno == EAGAIN);
+
+ errno = 0;
+ rv = ioctl(fd, I2C_RDWR, &payload);
+ rtems_test_assert(rv == -1);
+ rtems_test_assert(errno == EAGAIN);
+
+ sc = rtems_event_send(id, RTEMS_EVENT_1);
+ rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+ sc = rtems_event_receive(
+ RTEMS_EVENT_1,
+ RTEMS_EVENT_ANY | RTEMS_WAIT,
+ 100,
+ &e
+ );
+ rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+ sc = rtems_task_delete(id);
+ rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
+ rv = fcntl(fd, F_SETFL, flags);
+ rtems_test_assert(rv != -1);
+}
+
static void test_gpio_nxp_pca9535(void)
{
int rv;
@@ -627,6 +745,7 @@ static void test(void)
rtems_test_assert(bus->base.timeout == 0);
test_simple_read_write(bus, fd);
+ test_nonblock_read_write(bus, fd);
test_eeprom(bus);
test_gpio_nxp_pca9535();
test_switch_nxp_pca9548a();
@@ -657,7 +776,7 @@ static void Init(rtems_task_argument arg)
#define CONFIGURE_MAXIMUM_FILE_DESCRIPTORS 7
-#define CONFIGURE_MAXIMUM_TASKS 1
+#define CONFIGURE_MAXIMUM_TASKS 2
#define CONFIGURE_MAXIMUM_SEMAPHORES 1
--
2.26.2
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