Re: [PATCH v2 1/3] i3c: Drop support for I2C 10 bit addresing

Boris Brezillon
2019-02-27T12:10:14Z

Hi Vitor,

On Wed, 27 Feb 2019 12:05:30 +0000
vitor <vitor.soares@synopsys.com> wrote:

> On 26/02/19 14:28, Przemyslaw Gaj wrote:
> > This patch dropps support for I2C devices with 10 bit addressing. When I2C
> > device with 10 bit address is defined in DT, I3C master registration fails.
> >
> > Signed-off-by: Przemyslaw Gaj <pgaj@cadence.com>
> >
> > ---
> >
> > Main changes between v1 and v2 are:
> > - Add error message when registering I2C device with 10 bit address.
> >
> > ---
> > drivers/i3c/master.c | 9 +++++++++
> > 1 file changed, 9 insertions(+)
> >
> > diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
> > index 2dc628d..8c1e365 100644
> > --- a/drivers/i3c/master.c
> > +++ b/drivers/i3c/master.c
> > @@ -1962,6 +1962,15 @@ of_i3c_master_add_i2c_boardinfo(struct i3c_master_controller *master,
> > if (ret)
> > return ret;
> >
> > + /* The I3C Specification does not clearly say I2C devices with 10-bit
> > + * address are supported. These devices can't be passed properly through
> > + * DEFSLVS command.
> > + */
>
> IMO we just need to say 10-bit address not used or not supported in i3c.

I'd like to keep a clear comment on why it cannot supported right now
even though the spec is unclear about that. If the spec is updated to
state that I2C devs using extended addresses are forbidden, then we'll
update this comment accordingly.

>
> > + if (boardinfo->base.flags & I2C_CLIENT_TEN) {
> > + dev_err(&master->dev, "I2C device with 10 bit address not supported.");
> > + return -ENOTSUPP;
> > + }
> > +
> > /* LVR is encoded in reg[2]. */
> > boardinfo->lvr = reg[2];
> >
>
> Also need to change:
>
> #define I2C_MAX_ADDR            GENMASK(9, 0)
> to
> #define I2C_MAX_ADDR            GENMASK(6, 0)
> in master.h file

Yep, you can reduce the address space.

>
> Not sure about:
> unsigned long addrslots[((I2C_MAX_ADDR + 1) * 2) / BITS_PER_LONG];
> @Boris can you check this part?

This part is still valid, no need to update it as you already updated
I2C_MAX_ADDR.

Thanks for the review.

Boris