On 9/7/22 02:10, Peter Rosin wrote:
Hi!
First off, I'm very sorry for being too busy and too unresponsive.
2022-09-06 at 22:28, Eddie James wrote:
Use the new mux root operations to lock the root adapter while waiting for
the reset to complete. I2C commands issued after the SI7020 is starting up
or after reset can potentially upset the startup sequence. Therefore, the
host needs to wait for the startup sequence to finish before issuing
further I2C commands.
Signed-off-by: Eddie James <eajames@xxxxxxxxxxxxx>
---
drivers/iio/humidity/si7020.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/drivers/iio/humidity/si7020.c b/drivers/iio/humidity/si7020.c
index ab6537f136ba..76ca7863f35b 100644
--- a/drivers/iio/humidity/si7020.c
+++ b/drivers/iio/humidity/si7020.c
@@ -106,6 +106,7 @@ static const struct iio_info si7020_info = {
static int si7020_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
+ struct i2c_adapter *root;
struct iio_dev *indio_dev;
struct i2c_client **data;
int ret;
@@ -115,13 +116,24 @@ static int si7020_probe(struct i2c_client *client,
I2C_FUNC_SMBUS_READ_WORD_DATA))
return -EOPNOTSUPP;
+ root = i2c_lock_select_bus(client->adapter);
+ if (IS_ERR(root))
+ return PTR_ERR(root);
+
/* Reset device, loads default settings. */
- ret = i2c_smbus_write_byte(client, SI7020CMD_RESET);
- if (ret < 0)
+ ret = __i2c_smbus_xfer(root, client->addr, client->flags,
+ I2C_SMBUS_WRITE, SI7020CMD_RESET,
+ I2C_SMBUS_BYTE, NULL);
I'd say that this is too ugly. We should not add stuff that basically
hides the actual xfer from the mux like this. That is too much of a
break in the abstraction.
Hm, I guess I'm not sure I follow - I see several drivers that use the
raw __i2c_smbus_xfer or __i2c_transfer, some without a lock in sight. If
it's not acceptable to use the unlocked versions in some cases, why are
they exported in the header file?
Looking back, expanding on the previous series [1] so that it installs
the hook on the root adapter, handles smbus xfers and clears out the
callback afterwards is much more sensible. No?
Maybe so, though adding the callback is a more intrusive change, in my
opinion, since every transfer has to check if the pointer is null.
Thanks for your feedback!
Eddie
Maybe the callback in that series should also include a reference to
the xfer that has just been done, so that the hook can potentially
discriminate and only do the delay for the key xfer. But maybe that's
overkill?
Cheers,
Peter
[1] https://lore.kernel.org/lkml/20220518204119.38943-1-eajames@xxxxxxxxxxxxx/
+ if (ret < 0) {
+ i2c_unlock_deselect_bus(client->adapter);
return ret;
+ }
+
/* Wait the maximum power-up time after software reset. */
msleep(15);
+ i2c_unlock_deselect_bus(client->adapter);
+
indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
if (!indio_dev)
return -ENOMEM;
