| Message ID | 20120717170243.5def41a3@endymion.delvare (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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@ideasonboard.com> > > --- > > > > 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.
--- 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);