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

Boris Brezillon
2019-02-27T13:09:28Z

On Wed, 27 Feb 2019 12:52:42 +0000
vitor <vitor.soares@synopsys.com> wrote:

> Hi,
>
> On 27/02/19 12:10, Boris Brezillon wrote:
> > 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

Nitpick: please do not use net-style comments in the I3C subsystem.

Use

/*
* blablabla
*/

instead.

> >>> + * 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.
>
> I'm not sure if the terms aren't the same,

Don't understand what you mean, sorry.

>but let's keep the comment.
>
> >
> >>> + 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
>
> Also we can make i2c_algorithm.functionality = I2C_FUNC_SMBUS_EMUL | I2C_FUNC_I2C, and in this way we won't need ->i2c_func() and avoid the I2C_FUNC_10BIT_ADDR flag on host controller side.

Ack. Let's rip ->i2c_func() out and return I2C_FUNC_SMBUS_EMUL |
I2C_FUNC_I2C for everyone. We'll add it back if some drivers want to
support SMBUS natively or if 10bit addressing appears to be needed at
some point.