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drivers: i2c_nrfx_twim: refactor concat check logic

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The condition of being either the last message or not concatenable to
the next message is the inverse of the condition of committing to
concatenate the next message.  The latter is arguably easier to
understand.  Reverse the logic, document the conditions, and simplify
the early continue.

Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>
This commit is contained in:
Peter Bigot 2020-08-19 13:40:02 -05:00 • committed by Maureen Helm
commit faa855b9df
1 changed files with 26 additions and 18 deletions
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44
drivers/i2c/i2c_nrfx_twim.c
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@ -67,14 +67,22 @@ static int i2c_nrfx_twim_transfer(struct device *dev, struct i2c_msg *msgs,
break;
}
bool last_or_non_concatenable =
((msgs[i].flags & I2C_MSG_STOP)
|| !(i + 1 < num_msgs)
|| (msgs[i + 1].flags & I2C_MSG_RESTART)
|| ((msgs[i + 1].flags & I2C_MSG_READ)
!= (msgs[i].flags & I2C_MSG_READ)));
/* Merge this fragment with the next if it's not the last
* fragment, this one doesn't end a bus transaction, the next
* one doesn't start a bus transaction, and the direction of
* the next fragment is the same as this one.
*/
bool concat_next = ((i + 1) < num_msgs)
&& !(msgs[i].flags & I2C_MSG_STOP)
&& !(msgs[i + 1].flags & I2C_MSG_RESTART)
&& ((msgs[i].flags & I2C_MSG_READ)
== (msgs[i + 1].flags & I2C_MSG_READ));
if ((concat_len != 0) || !last_or_non_concatenable) {
/* If we need to concatenate the next message, or we've
* already committed to concatenate this message, add it to
* the buffer after verifying there's room.
*/
if (concat_next || (concat_len != 0)) {
if ((concat_len + msgs[i].len) > concat_buf_size) {
LOG_ERR("concat-buf overflow: %u + %u > %u",
concat_len, msgs[i].len, concat_buf_size);
@ -89,20 +97,20 @@ static int i2c_nrfx_twim_transfer(struct device *dev, struct i2c_msg *msgs,
concat_len += msgs[i].len;
}
if (last_or_non_concatenable) {
if (concat_len == 0) {
cur_xfer.p_primary_buf = msgs[i].buf;
cur_xfer.primary_length = msgs[i].len;
} else {
cur_xfer.p_primary_buf = concat_buf;
cur_xfer.primary_length = concat_len;
}
cur_xfer.type = (msgs[i].flags & I2C_MSG_READ) ?
NRFX_TWIM_XFER_RX : NRFX_TWIM_XFER_TX;
} else {
if (concat_next) {
continue;
}
if (concat_len == 0) {
cur_xfer.p_primary_buf = msgs[i].buf;
cur_xfer.primary_length = msgs[i].len;
} else {
cur_xfer.p_primary_buf = concat_buf;
cur_xfer.primary_length = concat_len;
}
cur_xfer.type = (msgs[i].flags & I2C_MSG_READ) ?
NRFX_TWIM_XFER_RX : NRFX_TWIM_XFER_TX;
nrfx_err_t res = nrfx_twim_xfer(&get_dev_config(dev)->twim,
&cur_xfer,
(msgs[i].flags & I2C_MSG_STOP) ?