Hi Jean,
On Tuesday 17 July 2012 17:02:43 Jean Delvare wrote:
> 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 <laurent.pinchart@xxxxxxxxxxxxxxxx>
> > ---
> >
> > 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().
I'm fine with that.
--
Regards,
Laurent Pinchart
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