Hi Laurent,
On Tue, 26 Jun 2012 16:17:08 +0200, Laurent Pinchart wrote:
> Adapter drivers might support only a subset of the SMBus operations
> natively. Those drivers currently have to manually emulate unsupported
> operations using I2C.
>
> Make the i2c_smbus_xfer() function fall back to
> i2c_smbus_xfer_emulated() when the adapter's .smbus_xfer() operation
> returns -EOPNOTSUPP, like it already does when the .smbus_xfer()
> operation isn't available at all.
>
> Signed-off-by: Laurent Pinchart <[email protected]>
> ---
> drivers/i2c/i2c-core.c | 9 +++++++--
> 1 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> index 8cfa660..16e750e 100644
> --- a/drivers/i2c/i2c-core.c
> +++ b/drivers/i2c/i2c-core.c
> @@ -2113,8 +2113,8 @@ s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16
> addr, unsigned short flags,
> union i2c_smbus_data *data)
> {
> unsigned long orig_jiffies;
> + s32 res = -EOPNOTSUPP;
> int try;
> - s32 res;
>
> flags &= I2C_M_TEN | I2C_CLIENT_PEC | I2C_CLIENT_SCCB;
>
> @@ -2134,7 +2134,12 @@ s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16
> addr, unsigned short flags,
> break;
> }
> i2c_unlock_adapter(adapter);
> - } else
> + }
> +
> + /* Fall back to i2c_smbus_xfer_emulated of the adapter doesn't implement
> + * native support for the SMBus operation.
> + */
> + if (res == -EOPNOTSUPP && adapter->algo->master_xfer)
> res = i2c_smbus_xfer_emulated(adapter, addr, flags, read_write,
> command, protocol, data);
>
Looks good overall, but maybe the following variant would be preferable
from a performance perspective:
--- linux-3.5-rc7.orig/drivers/i2c/i2c-core.c 2012-07-17 16:35:42.566799611
+0200
+++ linux-3.5-rc7/drivers/i2c/i2c-core.c 2012-07-17 16:59:55.334530352
+0200
@@ -2140,11 +2140,17 @@ s32 i2c_smbus_xfer(struct i2c_adapter *a
break;
}
i2c_unlock_adapter(adapter);
- } else
- res = i2c_smbus_xfer_emulated(adapter, addr, flags, read_write,
- command, protocol, data);
- return res;
+ if (res != -EOPNOTSUPP || !adapter->algo->master_xfer)
+ return res;
+ /*
+ * Fall back to i2c_smbus_xfer_emulated if the adapter doesn't
implement
+ * native support for the SMBus operation.
+ */
+ }
+
+ return i2c_smbus_xfer_emulated(adapter, addr, flags, read_write,
+ command, protocol, data);
}
EXPORT_SYMBOL(i2c_smbus_xfer);
What do you think? The advantage is that we can skip the tests for
adapters which only implement adapter->algo->master_xfer().
--
Jean Delvare
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