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Date:   Tue, 16 Jul 2019 15:40:13 +0200
From:   Boris Brezillon <boris.brezillon@collabora.com>
To:     Vitor Soares <Vitor.Soares@synopsys.com>
Cc:     "linux-iio@vger.kernel.org" <linux-iio@vger.kernel.org>,
        "linux-i3c@lists.infradead.org" <linux-i3c@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "lorenzo@kernel.org" <lorenzo@kernel.org>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "rafael@kernel.org" <rafael@kernel.org>,
        "bbrezillon@kernel.org" <bbrezillon@kernel.org>,
        "Joao.Pinto@synopsys.com" <Joao.Pinto@synopsys.com>
Subject: Re: [PATCH v4 3/3] iio: imu: st_lsm6dsx: add i3c basic support for
 LSM6DSO and LSM6DSR
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On Tue, 16 Jul 2019 13:22:25 +0000
Vitor Soares <Vitor.Soares@synopsys.com> wrote:

> Hi Boris,
> 
> From: Boris Brezillon <boris.brezillon@collabora.com>
> Date: Fri, Jul 12, 2019 at 21:03:20
> 
> > On Fri, 12 Jul 2019 18:40:14 +0000
> > Vitor Soares <Vitor.Soares@synopsys.com> wrote:
> >   
> > > From: Boris Brezillon <boris.brezillon@collabora.com>
> > > Date: Fri, Jul 12, 2019 at 17:43:23
> > >   
> > > > On Fri, 12 Jul 2019 16:28:02 +0000
> > > > Vitor Soares <Vitor.Soares@synopsys.com> wrote:
> > > >     
> > > > > From: Boris Brezillon <boris.brezillon@collabora.com>
> > > > > Date: Fri, Jul 12, 2019 at 17:14:29
> > > > >     
> > > > > > On Fri, 12 Jul 2019 13:53:30 +0200
> > > > > > Vitor Soares <Vitor.Soares@synopsys.com> wrote:
> > > > > >       
> > > > > > > For today the st_lsm6dsx driver support LSM6DSO and LSM6DSR sensor only in
> > > > > > > spi and i2c mode.
> > > > > > > 
> > > > > > > The LSM6DSO and LSM6DSR are also i3c capable so lets give i3c support to
> > > > > > > them.
> > > > > > > 
> > > > > > > Signed-off-by: Vitor Soares <vitor.soares@synopsys.com>
> > > > > > > Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
> > > > > > > ---
> > > > > > > Changes in v4:
> > > > > > >   Remove hw_id variable
> > > > > > > 
> > > > > > > Changes in v3:
> > > > > > >   Remove unnecessary st_lsm6dsx_i3c_data table used to hold device name
> > > > > > >   Use st_lsm6dsx_probe new form
> > > > > > > 
> > > > > > > Changes in v2:
> > > > > > >   Add support for LSM6DSR
> > > > > > >   Set pm_ops to st_lsm6dsx_pm_ops
> > > > > > > 
> > > > > > >  drivers/iio/imu/st_lsm6dsx/Kconfig          |  8 +++-
> > > > > > >  drivers/iio/imu/st_lsm6dsx/Makefile         |  1 +
> > > > > > >  drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_i3c.c | 58 +++++++++++++++++++++++++++++
> > > > > > >  3 files changed, 66 insertions(+), 1 deletion(-)
> > > > > > >  create mode 100644 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_i3c.c
> > > > > > > 
> > > > > > > diff --git a/drivers/iio/imu/st_lsm6dsx/Kconfig b/drivers/iio/imu/st_lsm6dsx/Kconfig
> > > > > > > index 9e59297..6b5a73c 100644
> > > > > > > --- a/drivers/iio/imu/st_lsm6dsx/Kconfig
> > > > > > > +++ b/drivers/iio/imu/st_lsm6dsx/Kconfig
> > > > > > > @@ -1,11 +1,12 @@
> > > > > > >  
> > > > > > >  config IIO_ST_LSM6DSX
> > > > > > >  	tristate "ST_LSM6DSx driver for STM 6-axis IMU MEMS sensors"
> > > > > > > -	depends on (I2C || SPI)
> > > > > > > +	depends on (I2C || SPI || I3C)
> > > > > > >  	select IIO_BUFFER
> > > > > > >  	select IIO_KFIFO_BUF
> > > > > > >  	select IIO_ST_LSM6DSX_I2C if (I2C)
> > > > > > >  	select IIO_ST_LSM6DSX_SPI if (SPI_MASTER)
> > > > > > > +	select IIO_ST_LSM6DSX_I3C if (I3C)
> > > > > > >  	help
> > > > > > >  	  Say yes here to build support for STMicroelectronics LSM6DSx imu
> > > > > > >  	  sensor. Supported devices: lsm6ds3, lsm6ds3h, lsm6dsl, lsm6dsm,
> > > > > > > @@ -23,3 +24,8 @@ config IIO_ST_LSM6DSX_SPI
> > > > > > >  	tristate
> > > > > > >  	depends on IIO_ST_LSM6DSX
> > > > > > >  	select REGMAP_SPI
> > > > > > > +
> > > > > > > +config IIO_ST_LSM6DSX_I3C
> > > > > > > +	tristate
> > > > > > > +	depends on IIO_ST_LSM6DSX
> > > > > > > +	select REGMAP_I3C
> > > > > > > diff --git a/drivers/iio/imu/st_lsm6dsx/Makefile b/drivers/iio/imu/st_lsm6dsx/Makefile
> > > > > > > index e5f733c..c676965 100644
> > > > > > > --- a/drivers/iio/imu/st_lsm6dsx/Makefile
> > > > > > > +++ b/drivers/iio/imu/st_lsm6dsx/Makefile
> > > > > > > @@ -4,3 +4,4 @@ st_lsm6dsx-y := st_lsm6dsx_core.o st_lsm6dsx_buffer.o \
> > > > > > >  obj-$(CONFIG_IIO_ST_LSM6DSX) += st_lsm6dsx.o
> > > > > > >  obj-$(CONFIG_IIO_ST_LSM6DSX_I2C) += st_lsm6dsx_i2c.o
> > > > > > >  obj-$(CONFIG_IIO_ST_LSM6DSX_SPI) += st_lsm6dsx_spi.o
> > > > > > > +obj-$(CONFIG_IIO_ST_LSM6DSX_I3C) += st_lsm6dsx_i3c.o
> > > > > > > diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_i3c.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_i3c.c
> > > > > > > new file mode 100644
> > > > > > > index 0000000..2e89524
> > > > > > > --- /dev/null
> > > > > > > +++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_i3c.c
> > > > > > > @@ -0,0 +1,58 @@
> > > > > > > +// SPDX-License-Identifier: GPL-2.0
> > > > > > > +/*
> > > > > > > + * Copyright (c) 2018 Synopsys, Inc. and/or its affiliates.
> > > > > > > + *
> > > > > > > + * Author: Vitor Soares <vitor.soares@synopsys.com>
> > > > > > > + */
> > > > > > > +
> > > > > > > +#include <linux/kernel.h>
> > > > > > > +#include <linux/module.h>
> > > > > > > +#include <linux/i3c/device.h>
> > > > > > > +#include <linux/i3c/master.h>
> > > > > > > +#include <linux/slab.h>
> > > > > > > +#include <linux/of.h>
> > > > > > > +#include <linux/regmap.h>
> > > > > > > +
> > > > > > > +#include "st_lsm6dsx.h"
> > > > > > > +
> > > > > > > +static const struct i3c_device_id st_lsm6dsx_i3c_ids[] = {
> > > > > > > +	I3C_DEVICE(0x0104, 0x006C, (void *)ST_LSM6DSO_ID),
> > > > > > > +	I3C_DEVICE(0x0104, 0x006B, (void *)ST_LSM6DSR_ID),      
> > > > > > 
> > > > > > I think you need an uintptr_t cast here:
> > > > > > 
> > > > > > 	I3C_DEVICE(0x0104, 0x006C, (void *)(uintptr_t)ST_LSM6DSO_ID),
> > > > > > 	I3C_DEVICE(0x0104, 0x006B, (void *)(uintptr_t)ST_LSM6DSR_ID),
> > > > > > 
> > > > > > otherwise gcc might complain that the integer and pointer do not have
> > > > > > the same size (on 64-bit architectures).      
> > > > > 
> > > > > I don't understand this part. Can you provide or point some background?    
> > > > 
> > > > If you don't do that you'll get the following warning:
> > > > 
> > > > 	warning: cast to 'void *' from smaller integer type 'int' [-Wint-to-void-pointer-cast]    
> > > 
> > > I don't get the warning during compilation. Is there any flag to enable 
> > > or so?  
> > 
> > Nope, nothing specific to enable, just enable this driver on an arm64
> > config. Note that that gcc doesn't seem to complain about this
> > int -> void * cast (there's probably some kind of auto-promotion to
> > pointer size), but it does complains about the following void * -> int
> > cast:
> > 
> > drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_i3c.c: In function ‘st_lsm6dsx_i3c_probe’:
> > drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_i3c.c:43:43: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
> >    43 |  return st_lsm6dsx_probe(&i3cdev->dev, 0, (int)id->data, regmap);
> >       |       
> 
> I fixed the warning by changing:
> 
> st_lsm6dsx_probe(&i3cdev->dev, 0, (int)id->data, regmap);
> 
> to
> 
> st_lsm6dsx_probe(&i3cdev->dev, 0, (int)(uintptr_t)id->data, regmap);

The (int) cast is implicit, no need to add it here.

> 
> But I wonder if it isn't more save to change the following too:
> 	I3C_DEVICE(0x0104, 0x006C, (void *)(uintptr_t)ST_LSM6DSO_ID),
> 	I3C_DEVICE(0x0104, 0x006B, (void *)(uintptr_t)ST_LSM6DSR_ID),
> 
> What do you think?

I think we're good, we would have a problem if you were defining
ST_LSM6DSO_ID as an ULL (unsigned long long, AKA u64) and trying to
cast that value to a void pointer on a 32-bit arch.