[1/2] usb: typec: tps6598x: handle block reads separately with plain-I2C adapters

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

On Fri, Apr 20, 2018 at 10:26:08AM -0700, Guenter Roeck wrote:
> On Wed, Apr 18, 2018 at 03:34:09PM +0300, Heikki Krogerus wrote:
> > If the I2C adapter that the PD controller is attached to
> > does not support SMBus protocol, the driver needs to handle
> > block reads separately. The first byte returned in block
> > read protocol will show the total number of bytes. It needs
> > to be stripped away.
> > 
> > This is handled separately in the driver only because right
> > now we have no way of requesting the used protocol with
> > regmap-i2c. This is in practice a workaround for what is
> > really a problem in regmap-i2c. The other option would have
> > been to register custom regmap, or not use regmap at all,
> > however, since the solution is very simple, I choose to use
> > it in this case for convenience. It is easy to remove once
> > we figure out how to handle this kind of cases in
> > regmap-i2c.
> > 
> > Fixes: 0a4c005bd171 ("usb: typec: driver for TI TPS6598x USB Power Delivery controllers")
> > Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> > ---
> >  drivers/usb/typec/tps6598x.c | 42 ++++++++++++++++++++++++++++++------
> >  1 file changed, 35 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/usb/typec/tps6598x.c b/drivers/usb/typec/tps6598x.c
> > index 8b8406867c02..82f09cd9792d 100644
> > --- a/drivers/usb/typec/tps6598x.c
> > +++ b/drivers/usb/typec/tps6598x.c
> > @@ -73,6 +73,7 @@ struct tps6598x {
> >  	struct device *dev;
> >  	struct regmap *regmap;
> >  	struct mutex lock; /* device lock */
> > +	u8 i2c_protocol:1;
> >  
> >  	struct typec_port *port;
> >  	struct typec_partner *partner;
> > @@ -80,6 +81,23 @@ struct tps6598x {
> >  	struct typec_capability typec_cap;
> >  };
> >  
> > +static int
> > +tps6598x_block_read(struct tps6598x *tps, u8 reg, void *val, ssize_t len)
> > +{
> > +	u8 data[len + 1];
> > +	int ret;
> > +
> > +	if (!tps->i2c_protocol)
> > +		return regmap_raw_read(tps->regmap, reg, val, len);
> > +
> > +	ret = regmap_raw_read(tps->regmap, reg, data, sizeof(data));
> > +	if (ret)
> > +		return ret;
> > +
> 
> Sanity check ?
> 	if (data[0] != len)
> 		return -Esomething;

No. Then we would not even need the len parameter. The idea is to
allow reading a number of bytes specified by caller, regardless of the
maximum size of the block.


Thanks,