Re: [alsa-devel] [PATCH 06/14] soundwire: Add IO transfer

[Takashi Iwai]

On Fri, 20 Oct 2017 07:30:06 +0200,
Vinod Koul wrote:
> 
> On Thu, Oct 19, 2017 at 11:13:48AM +0200, Takashi Iwai wrote:
> > On Thu, 19 Oct 2017 05:03:22 +0200,
> > Vinod Koul wrote:
> > > 
> > > +/**
> > > + * sdw_transfer: Synchronous transfer message to a SDW Slave device
> > > + *
> > > + * @bus: SDW bus
> > > + * @slave: SDW Slave
> > > + * @msg: SDW message to be xfered
> > > + */
> > > +int sdw_transfer(struct sdw_bus *bus, struct sdw_slave *slave,
> > > +					struct sdw_msg *msg)
> > > +{
> > > +	bool page;
> > > +	int ret;
> > > +
> > > +	mutex_lock(&bus->msg_lock);
> > > +
> > > +	page = sdw_get_page(slave, msg);
> > > +
> > > +	ret = do_transfer(bus, msg, page);
> > > +	if (ret != 0 && ret != -ENODATA) {
> > > +		dev_err(bus->dev, "trf on Slave %d failed:%d\n",
> > > +				msg->dev_num, ret);
> > > +		goto error;
> > > +	}
> > > +
> > > +	if (page)
> > > +		ret = sdw_reset_page(bus, msg->dev_num);
> > > +
> > > +error:
> > > +	mutex_unlock(&bus->msg_lock);
> > > +
> > > +	return ret;
> > 
> > So the logic here is that when -ENODATA is returned and page is false,
> > this function should return -ENODATA to the caller,  but when page
> > is set, it returns 0?
> 
> Sorry no. do_transfer can succced (0) or in some case where Slaves didn't
> care for return error (ENODATA), or other errors.
> No ENODATA can be error depending on message sent so we dont treat this as
> failure and let caller decide.
> 
> In case of errors (others) we don't need to reset page and we bail out

Well, the question is the handling of ENODATA.  Whether the function
returns 0 or -ENODATA depends on page flag.  If page flag is true,
-ENODATA is cleared.  My question was whether this behavior is
intended or not.

If -ENODATA should be returned whenever it gets that from
do_transfer(), the code has a potential bug there.


Takashi