On Mon, Aug 06, 2012 at 03:15:17PM +0000, Opensource [Anthony Olech] wrote:
> I do realize that REGMAP does locking on individual register accesses, > however, the each GPIO line is controlled by 4-bits in a register, with > the meaning of the most significant bit depending on the GPIO direction, > so it is essential that the register be read first before do an update, thus > two sequential register accesses must be protected by a mutex to > prevent another process changing the register (and hence the meaning > of the most-significant bit) in the middle of the two accesses. > I hope this explains to your satisfaction why a driver mutex is required > in addition to the regmap's register access mutex This seems a bit excessive and complicated - I'd be inclined to either just say that the caller is responsible for avoiding confusion here (obviously if you're changing the direction there's a race anyway) or store the data in a variable locally rather than having to do I/O on the device under lock every time it's interacted with. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
