[RFC/PATCH 2/3] i2c: Fall back to emulated SMBus if the operation isn't supported natively

2012-06-26 Thread Laurent Pinchart 
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 
---
 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);
 
-- 
1.7.3.4

--
To unsubscribe from this list: send the line "unsubscribe linux-omap" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [RFC/PATCH 2/3] i2c: Fall back to emulated SMBus if the operation isn't supported natively

2012-07-17 Thread Jean Delvare 
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 
> ---
>  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.c2012-07-17 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
--
To unsubscribe from this list: send the line "unsubscribe linux-omap" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [RFC/PATCH 2/3] i2c: Fall back to emulated SMBus if the operation isn't supported natively

2012-07-17 Thread Laurent Pinchart 
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 
> > ---
> > 
> >  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.c2012-07-17
> 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

--
To unsubscribe from this list: send the line "unsubscribe linux-omap" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html