Re: [RFC 02/11] i2c: add quirk checks to core

[Sergei Shtylyov]

Hello.

On 01/09/2015 11:45 PM, Wolfram Sang wrote:

> > > Let the core do the checks if HW quirks prevent a transfer. Saves code
> > >from drivers and adds consistency.

> > > Signed-off-by: Wolfram Sang <wsa@xxxxxxxxxxxxx>
> > > ---
> > >   drivers/i2c/i2c-core.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++
> > >   1 file changed, 53 insertions(+)
> > >
> > > diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> > > index 39d25a8cb1ad..7b10a19abf5b 100644
> > > --- a/drivers/i2c/i2c-core.c
> > > +++ b/drivers/i2c/i2c-core.c
> > > @@ -2063,6 +2063,56 @@ module_exit(i2c_exit);
> > >    * ----------------------------------------------------
> > >    */
> > >
> > > +/* Check if val is exceeding the quirk IFF quirk is non 0 */
> > > +#define i2c_quirk_exceeded(val, quirk) ((quirk) && ((val) > (quirk)))
> > > +
> > > +static int i2c_quirk_error(struct i2c_adapter *adap, struct i2c_msg *msg, char *err_msg)
> > > +{
> > > +	dev_err(&adap->dev, "quirk: %s (addr 0x%04x, size %u)\n", err_msg, msg->addr, msg->len);
> > > +	return -EOPNOTSUPP;
> > > +}

> >     Always returning the same value doesn't make much sense. Are you trying
> > to save space on the call sites?

> Please elaborate. I think it does. If a quirk matches, we report that we
> don't support this transfer.

   OK, but what's the point of having this function return *int* if it always 
returns the same value? AFAIU, you're trying to save the code space on the 
call sites of this function by not having *return* -EOPNOTSUPP there each time?

> > [...]
> > > @@ -2080,6 +2130,9 @@ int __i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
> > >   	unsigned long orig_jiffies;
> > >   	int ret, try;
> > >
> > > +	if (adap->quirks && i2c_check_for_quirks(adap, msgs, num))

> >     So, you only check for non-zero result of this function? Perhaps it makes
> > sense to return true/false instead?

> Could be done, but what would be the advantage? A lot of functions
> return errno or 0.

   It would have been OK if you were actually caring about the result, e.g. 
returning it from __i2c_transfer(). Since you don't, IMO it would make more 
sense to return true from i2c_check_for_quirks() (making it *bool*) iff it did 
find/apply a quirk.

WBR, Sergei

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