Subject: Re: [RFC V2 04/12] i2c: opal: make use of the new infrastructure for quirks

From: Benjamin Herrenschmidt <[email-masked]>
Date: Wed, 11 Mar 2015 10:12:13 +1100

On Tue, 2015-03-10 at 22:43 +0530, Neelesh Gupta wrote:
> I tested the i2c opal driver after updating the patch as below.
> Basically I think we can also support write-then-{read/write}
> for the number of messages = 2.
> Ben, any issues if we support both write plus read/write in the
> opal driver ?

Nope, in fact it's a good idea, I found myself having to expoes such
an interface to some userspace tool of ours.

However...

> diff --git a/drivers/i2c/busses/i2c-opal.c b/drivers/i2c/busses/i2c-opal.c
> index 16f90b1..85412ba 100644
> --- a/drivers/i2c/busses/i2c-opal.c
> +++ b/drivers/i2c/busses/i2c-opal.c
> @@ -104,18 +104,8 @@ static int i2c_opal_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
>   		req.buffer_ra = cpu_to_be64(__pa(msgs[0].buf));
>   		break;
>   	case 2:
> -		/* For two messages, we basically support only simple
> -		 * smbus transactions of a write plus a read. We might
> -		 * want to allow also two writes but we'd have to bounce
> -		 * the data into a single buffer.
> -		 */
> -		if ((msgs[0].flags & I2C_M_RD) || !(msgs[1].flags & I2C_M_RD))
> -			return -EOPNOTSUPP;

Don't we still want to enforce that the first message is a write ?
Somebody may not be looking at the quirks...

> -		if (msgs[0].len > 4)
> -			return -EOPNOTSUPP;

And that the len is supported...

> -		if (msgs[0].addr != msgs[1].addr)
> -			return -EOPNOTSUPP;

Same...

Ie, the quirk indicates to the callers what we support, but we should
still check that we aren't called with something that doesn't match.

> -		req.type = OPAL_I2C_SM_READ;
> +		req.type = (msgs[1].flags & I2C_M_RD) ?
> +			OPAL_I2C_SM_READ : OPAL_I2C_SM_WRITE;
>   		req.addr = cpu_to_be16(msgs[0].addr);
>   		req.subaddr_sz = msgs[0].len;
>   		for (i = 0; i < msgs[0].len; i++)
> @@ -210,6 +200,11 @@ static const struct i2c_algorithm i2c_opal_algo = {
>   	.functionality	= i2c_opal_func,
>   };
> 
> +static struct i2c_adapter_quirks i2c_opal_quirks = {
> +	.flags = I2C_AQ_COMB | I2C_AQ_COMB_WRITE_FIRST | I2C_AQ_COMB_SAME_ADDR,
> +	.max_comb_1st_msg_len = 4,
> +};
> +
>   static int i2c_opal_probe(struct platform_device *pdev)
>   {
>   	struct i2c_adapter	*adapter;
> @@ -232,6 +227,7 @@ static int i2c_opal_probe(struct platform_device *pdev)
> 
>   	adapter->algo = &i2c_opal_algo;
>   	adapter->algo_data = (void *)(unsigned long)opal_id;
> +	adapter->quirks = &i2c_opal_quirks;
>   	adapter->dev.parent = &pdev->dev;
>   	adapter->dev.of_node = of_node_get(pdev->dev.of_node);
>   	pname = of_get_property(pdev->dev.of_node, "ibm,port-name", NULL);
> 
> 
> 
> On 02/25/2015 09:31 PM, Wolfram Sang wrote:
> > From: Wolfram Sang <[email-masked]>
> >
> > Signed-off-by: Wolfram Sang <[email-masked]>
> > ---
> >   drivers/i2c/busses/i2c-opal.c | 22 +++++++++++-----------
> >   1 file changed, 11 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-opal.c b/drivers/i2c/busses/i2c-opal.c
> > index 16f90b1a750894..b2788ecad5b3cb 100644
> > --- a/drivers/i2c/busses/i2c-opal.c
> > +++ b/drivers/i2c/busses/i2c-opal.c
> > @@ -104,17 +104,6 @@ static int i2c_opal_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> >   		req.buffer_ra = cpu_to_be64(__pa(msgs[0].buf));
> >   		break;
> >   	case 2:
> > -		/* For two messages, we basically support only simple
> > -		 * smbus transactions of a write plus a read. We might
> > -		 * want to allow also two writes but we'd have to bounce
> > -		 * the data into a single buffer.
> > -		 */
> > -		if ((msgs[0].flags & I2C_M_RD) || !(msgs[1].flags & I2C_M_RD))
> > -			return -EOPNOTSUPP;
> > -		if (msgs[0].len > 4)
> > -			return -EOPNOTSUPP;
> > -		if (msgs[0].addr != msgs[1].addr)
> > -			return -EOPNOTSUPP;
> >   		req.type = OPAL_I2C_SM_READ;
> >   		req.addr = cpu_to_be16(msgs[0].addr);
> >   		req.subaddr_sz = msgs[0].len;
> > @@ -210,6 +199,16 @@ static const struct i2c_algorithm i2c_opal_algo = {
> >   	.functionality	= i2c_opal_func,
> >   };
> >   
> > +/* For two messages, we basically support only simple
> > + * smbus transactions of a write plus a read. We might
> > + * want to allow also two writes but we'd have to bounce
> > + * the data into a single buffer.
> > + */
> > +static struct i2c_adapter_quirks i2c_opal_quirks = {
> > +	.flags = I2C_AQ_COMB_WRITE_THEN_READ,
> > +	.max_comb_1st_msg_len = 4,
> > +};
> > +
> >   static int i2c_opal_probe(struct platform_device *pdev)
> >   {
> >   	struct i2c_adapter	*adapter;
> > @@ -232,6 +231,7 @@ static int i2c_opal_probe(struct platform_device *pdev)
> >   
> >   	adapter->algo = &i2c_opal_algo;
> >   	adapter->algo_data = (void *)(unsigned long)opal_id;
> > +	adapter->quirks = &i2c_opal_quirks;
> >   	adapter->dev.parent = &pdev->dev;
> >   	adapter->dev.of_node = of_node_get(pdev->dev.of_node);
> >   	pname = of_get_property(pdev->dev.of_node, "ibm,port-name", NULL);