lkml.org 
[lkml]   [2018]   [Oct]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH v8 05/10] dt-bindings: i3c: Add macros to help fill I3C/I2C device's reg property
    On Wed, 03 Oct 2018 11:37:17 -0700
    Joe Perches <joe@perches.com> wrote:

    > On Wed, 2018-10-03 at 15:22 +0200, Boris Brezillon wrote:
    > > The reg property of devices connected to an I3C bus have 3 cells, and
    > > filling them manually is not trivial. Provides macros to help doing
    > > that.
    >
    > This patch logic seems excessively fragile.

    Keep in mind that this header is meant to be include by .dts(i) files,
    not regular .c files.

    >
    > > Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
    > > Reviewed-by: Rob Herring <robh@kernel.org>
    > > ---
    > > Changes in v8:
    > > - None
    > >
    > > Changes in v5:
    > > - none
    > > ---
    > > include/dt-bindings/i3c/i3c.h | 28 ++++++++++++++++++++++++++++
    > > 1 file changed, 28 insertions(+)
    > > create mode 100644 include/dt-bindings/i3c/i3c.h
    > >
    > > diff --git a/include/dt-bindings/i3c/i3c.h b/include/dt-bindings/i3c/i3c.h
    > > new file mode 100644
    > > index 000000000000..97448c546649
    > > --- /dev/null
    > > +++ b/include/dt-bindings/i3c/i3c.h
    > > @@ -0,0 +1,28 @@
    > > +/* SPDX-License-Identifier: GPL-2.0 */
    > > +/*
    > > + * Copyright (C) 2017 Cadence Design Systems Inc.
    > > + *
    > > + * Author: Boris Brezillon <boris.brezillon@bootlin.com>
    > > + */
    > > +
    > > +#ifndef _DT_BINDINGS_I3C_I3C_H
    > > +#define _DT_BINDINGS_I3C_I3C_H
    > > +
    > > +#define IS_I2C_DEV 0x80000000
    > > +
    > > +#define I2C_DEV(addr, lvr) \
    > > + (addr) (IS_I2C_DEV | (lvr)) 0x0
    >
    > This looks to be missing surrounding parentheses.

    Actually it's not. The macro is supposed to declare 3 u32 integers each
    of them separated by a space:

    reg = <I2C_DEV(0x34, 0x1)>;

    is translated into

    reg = <0x34 0x80000001 0x0>;

    >
    > > +
    > > +#define I3C_PID(manufid, partid, instid, extrainfo) \
    > > + ((manufid) << 1) \
    > > + (((partid) << 16) | ((instid) << 12) | (extrainfo))
    >
    > This macro doesn't make any sense. Missing a shift and an or?

    Same here, the PID is taking 2 32-bit entries.

    Now, I agree that this is far from obvious, and if Rob is okay, I'd
    like to propose a different binding to avoid having to define these
    macros:

    reg = <i2c_addr_or_i3c_static_addr pid_msb pid_lsb>;

    If pid_msb and pid_lsb are 0, then the node is defining an I2C device
    (AFAICT, 0 is not a valid PID), otherwise it's an I3C device. This way
    we get rid of the IS_I2C_DEV flag, and we can get rid of those macros
    without making I3C dev node definition too painful (the only part
    developers will have to get right is the PID)

    >
    > > +
    > > +#define I3C_DEV_WITH_STATIC_ADDR(addr, manufid, partid, \
    > > + instid, extrainfo) \
    > > + (addr) I3C_PID(manufid, partid, instid, extrainfo)
    > > +
    > > +#define I3C_DEV(manufid, partid, instid, extrainfo) \
    > > + I3C_DEV_WITH_STATIC_ADDR(0x0, manufid, partid, \
    > > + instid, extrainfo)
    > > +
    > > +#endif
    >

    \
     
     \ /
      Last update: 2018-10-03 21:00    [W:4.404 / U:0.020 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site