The device cp2112 does not support i2c combined transactions,
since unable to suppress the stop bit between adjacent i2c
transactions.
For this reason, in commit b9029345ed6483fcadadc4834b44a5656dd56d70
("HID: cp2112: add I2C mode") I have omitted the support for
num > 1 in i2c_transfer().
But:
1) in few kernel drivers i2c_transfer() has been used to
simplify the code by replacing a sequence of i2c_master_send()
and i2c_master_recv(), e.g. in i2c-hid.c and iio subsystem.
Those drivers will fail if used with current cp2112 driver.
2) in drivers/i2c/busses/ there are already drivers that
implement i2c_transfer() as a sequence of elementary (not
combined) i2c transactions, e.g. i2c-bcm2835.c, i2c-puv3.c,
i2c-qup.c, i2c-robotfuzz-osif.c, i2c-viperboard.c, i2c-xlr.c.
To fix 1) and considering 2), rewrite i2c_transfer() in case
of num > 1 as a loop of non-combined i2c transactions.
Signed-off-by: Antonio Borneo <borneo.antonio@xxxxxxxxx>
---
Hi Benjamin,
In [1] we had a talk about implementing i2c_transfer() as a
sequence of elementary (not combined) i2c transactions.
After Jonathan's reply in [2], I went to check better the
existing I2C drivers and I changed opinion.
Added linux-i2c list in copy to get feedback, if any, from
the I2C experts.
Regards,
Antonio Borneo
[1] https://lkml.org/lkml/2014/6/29/6
[2] https://lkml.org/lkml/2014/7/15/104
drivers/hid/hid-cp2112.c | 76 ++++++++++++++++++++++++------------------------
1 file changed, 38 insertions(+), 38 deletions(-)
diff --git a/drivers/hid/hid-cp2112.c b/drivers/hid/hid-cp2112.c
index 3318de6..76cad81 100644
--- a/drivers/hid/hid-cp2112.c
+++ b/drivers/hid/hid-cp2112.c
@@ -444,8 +444,7 @@ static int cp2112_i2c_write_req(void *buf, u8 slave_address, u8 *data,
return data_length + 3;
}
-static int cp2112_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
- int num)
+static int cp2112_i2c_xfer_msg(struct i2c_adapter *adap, struct i2c_msg *msg)
{
struct cp2112_device *dev = (struct cp2112_device *)adap->algo_data;
struct hid_device *hdev = dev->hdev;
@@ -454,33 +453,18 @@ static int cp2112_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
unsigned int retries;
int ret;
- hid_dbg(hdev, "I2C %d messages\n", num);
-
- if (num != 1) {
- hid_err(hdev,
- "Multi-message I2C transactions not supported\n");
- return -EOPNOTSUPP;
- }
-
- if (msgs->flags & I2C_M_RD)
- count = cp2112_read_req(buf, msgs->addr, msgs->len);
+ if (msg->flags & I2C_M_RD)
+ count = cp2112_read_req(buf, msg->addr, msg->len);
else
- count = cp2112_i2c_write_req(buf, msgs->addr, msgs->buf,
- msgs->len);
-
+ count = cp2112_i2c_write_req(buf, msg->addr, msg->buf,
+ msg->len);
if (count < 0)
return count;
- ret = hid_hw_power(hdev, PM_HINT_FULLON);
- if (ret < 0) {
- hid_err(hdev, "power management error: %d\n", ret);
- return ret;
- }
-
ret = cp2112_hid_output(hdev, buf, count, HID_OUTPUT_REPORT);
if (ret < 0) {
hid_warn(hdev, "Error starting transaction: %d\n", ret);
- goto power_normal;
+ return ret;
}
for (retries = 0; retries < XFER_STATUS_RETRIES; ++retries) {
@@ -488,7 +472,7 @@ static int cp2112_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
if (-EBUSY == ret)
continue;
if (ret < 0)
- goto power_normal;
+ return ret;
break;
}
@@ -502,30 +486,46 @@ static int cp2112_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
hid_warn(hdev, "Error cancelling transaction: %d\n",
ret);
- ret = -ETIMEDOUT;
- goto power_normal;
+ return -ETIMEDOUT;
}
- if (!(msgs->flags & I2C_M_RD))
- goto finish;
+ if (!(msg->flags & I2C_M_RD))
+ return 0;
- ret = cp2112_read(dev, msgs->buf, msgs->len);
+ ret = cp2112_read(dev, msg->buf, msg->len);
if (ret < 0)
- goto power_normal;
- if (ret != msgs->len) {
- hid_warn(hdev, "short read: %d < %d\n", ret, msgs->len);
- ret = -EIO;
- goto power_normal;
+ return ret;
+ if (ret != msg->len) {
+ hid_warn(hdev, "short read: %d < %d\n", ret, msg->len);
+ return -EIO;
}
+ return 0;
+}
-finish:
- /* return the number of transferred messages */
- ret = 1;
+static int cp2112_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
+ int num)
+{
+ struct cp2112_device *dev = (struct cp2112_device *)adap->algo_data;
+ struct hid_device *hdev = dev->hdev;
+ int i, ret;
+
+ hid_dbg(hdev, "I2C %d messages\n", num);
+
+ ret = hid_hw_power(hdev, PM_HINT_FULLON);
+ if (ret < 0) {
+ hid_err(hdev, "power management error: %d\n", ret);
+ return ret;
+ }
+
+ for (i = 0; i < num; i++) {
+ ret = cp2112_i2c_xfer_msg(adap, &msgs[i]);
+ if (ret < 0)
+ break;
+ }
-power_normal:
hid_hw_power(hdev, PM_HINT_NORMAL);
hid_dbg(hdev, "I2C transfer finished: %d\n", ret);
- return ret;
+ return (ret < 0) ? ret : num;
}
static int cp2112_xfer(struct i2c_adapter *adap, u16 addr,
--
2.3.1
--
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