Re: [PATCH 02/10] iio: imu: adis: add unlocked read/write function versions

["Ardelean, Alexandru" <alexandru.Ardelean@analog.com>]

On Tue, 2019-10-08 at 06:54 +0000, Ardelean, Alexandru wrote:
> [External]
> 
> On Mon, 2019-10-07 at 22:16 +0100, Jonathan Cameron wrote:
> > On Sun, 6 Oct 2019 10:12:01 +0100
> > Jonathan Cameron <jic23@kernel.org> wrote:
> > 
> > > On Thu, 26 Sep 2019 14:18:04 +0300
> > > Alexandru Ardelean <alexandru.ardelean@analog.com> wrote:
> > > 
> > > > This will allow more flexible control to group reads & writes into
> > > > a
> > > > single
> > > > lock (particularly the state_lock).
> > > > 
> > > > The end-goal is to remove the indio_dev->mlock usage, and the
> > > > simplest fix
> > > > would have been to just add another lock, which would not be a good
> > > > idea on
> > > > the long-run.
> > > > 
> > > > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>  
> > > Applied to the togreg branch of iio.git and pushed out as testing
> > > etc.
> > > 
> > > Jonathan
> > > 
> > 0-day found a potential issue (kind of) in the read functions.
> > 
> > > > ---
> > > >  drivers/iio/imu/adis.c       |  34 +++++------
> > > >  include/linux/iio/imu/adis.h | 114
> > > > ++++++++++++++++++++++++++++++++++-
> > > >  2 files changed, 128 insertions(+), 20 deletions(-)
> > > > 
> > > > diff --git a/drivers/iio/imu/adis.c b/drivers/iio/imu/adis.c
> > > > index 3c2d896e3a96..4f3be011c898 100644
> > > > --- a/drivers/iio/imu/adis.c
> > > > +++ b/drivers/iio/imu/adis.c
> > > > @@ -26,7 +26,14 @@
> > > >  #define ADIS_MSC_CTRL_DATA_RDY_DIO2	BIT(0)
> > > >  #define ADIS_GLOB_CMD_SW_RESET		BIT(7)
> > > >  
> > > > -int adis_write_reg(struct adis *adis, unsigned int reg,
> > > > +/**
> > > > + * __adis_write_reg() - write N bytes to register (unlocked
> > > > version)
> > > > + * @adis: The adis device
> > > > + * @reg: The address of the lower of the two registers
> > > > + * @value: The value to write to device (up to 4 bytes)
> > > > + * @size: The size of the @value (in bytes)
> > > > + */
> > > > +int __adis_write_reg(struct adis *adis, unsigned int reg,
> > > >  	unsigned int value, unsigned int size)
> > > >  {
> > > >  	unsigned int page = reg / ADIS_PAGE_SIZE;
> > > > @@ -70,8 +77,6 @@ int adis_write_reg(struct adis *adis, unsigned
> > > > int
> > > > reg,
> > > >  		},
> > > >  	};
> > > >  
> > > > -	mutex_lock(&adis->state_lock);
> > > > -
> > > >  	spi_message_init(&msg);
> > > >  
> > > >  	if (adis->current_page != page) {
> > > > @@ -96,8 +101,7 @@ int adis_write_reg(struct adis *adis, unsigned
> > > > int
> > > > reg,
> > > >  		adis->tx[3] = value & 0xff;
> > > >  		break;
> > > >  	default:
> > > > -		ret = -EINVAL;
> > > > -		goto out_unlock;
> > > > +		return -EINVAL;
> > > >  	}
> > > >  
> > > >  	xfers[size].cs_change = 0;
> > > > @@ -113,20 +117,18 @@ int adis_write_reg(struct adis *adis,
> > > > unsigned
> > > > int reg,
> > > >  		adis->current_page = page;
> > > >  	}
> > > >  
> > > > -out_unlock:
> > > > -	mutex_unlock(&adis->state_lock);
> > > > -
> > > >  	return ret;
> > > >  }
> > > > -EXPORT_SYMBOL_GPL(adis_write_reg);
> > > > +EXPORT_SYMBOL_GPL(__adis_write_reg);
> > > >  
> > > >  /**
> > > > - * adis_read_reg() - read 2 bytes from a 16-bit register
> > > > + * __adis_read_reg() - read N bytes from register (unlocked
> > > > version)
> > > >   * @adis: The adis device
> > > >   * @reg: The address of the lower of the two registers
> > > >   * @val: The value read back from the device
> > > > + * @size: The size of the @val buffer
> > > >   */
> > > > -int adis_read_reg(struct adis *adis, unsigned int reg,
> > > > +int __adis_read_reg(struct adis *adis, unsigned int reg,
> > > >  	unsigned int *val, unsigned int size)
> > > >  {
> > > >  	unsigned int page = reg / ADIS_PAGE_SIZE;
> > > > @@ -188,15 +190,14 @@ int adis_read_reg(struct adis *adis, unsigned
> > > > int reg,
> > > >  		spi_message_add_tail(&xfers[3], &msg);
> > > >  		break;
> > > >  	default:
> > > > -		ret = -EINVAL;
> > > > -		goto out_unlock;
> > > > +		return -EINVAL;
> > > >  	}
> > > >  
> > > >  	ret = spi_sync(adis->spi, &msg);
> > > >  	if (ret) {
> > > >  		dev_err(&adis->spi->dev, "Failed to read register
> > > > 0x%02X:
> > > > %d\n",
> > > >  				reg, ret);
> > > > -		goto out_unlock;
> > > > +		return ret;
> > > >  	} else {
> > > >  		adis->current_page = page;
> > > >  	}
> > > > @@ -210,12 +211,9 @@ int adis_read_reg(struct adis *adis, unsigned
> > > > int reg,
> > > >  		break;
> > > >  	}
> > > >  
> > > > -out_unlock:
> > > > -	mutex_unlock(&adis->state_lock);
> > > > -
> > > >  	return ret;
> > > >  }
> > > > -EXPORT_SYMBOL_GPL(adis_read_reg);
> > > > +EXPORT_SYMBOL_GPL(__adis_read_reg);
> > > >  
> > > >  #ifdef CONFIG_DEBUG_FS
> > > >  
> > > > diff --git a/include/linux/iio/imu/adis.h
> > > > b/include/linux/iio/imu/adis.h
> > > > index 3ed5eceaac2d..3a028c40e04e 100644
> > > > --- a/include/linux/iio/imu/adis.h
> > > > +++ b/include/linux/iio/imu/adis.h
> > > > @@ -75,11 +75,121 @@ int adis_init(struct adis *adis, struct
> > > > iio_dev
> > > > *indio_dev,
> > > >  	struct spi_device *spi, const struct adis_data *data);
> > > >  int adis_reset(struct adis *adis);
> > > >  
> > > > -int adis_write_reg(struct adis *adis, unsigned int reg,
> > > > +int __adis_write_reg(struct adis *adis, unsigned int reg,
> > > >  	unsigned int val, unsigned int size);
> > > > -int adis_read_reg(struct adis *adis, unsigned int reg,
> > > > +int __adis_read_reg(struct adis *adis, unsigned int reg,
> > > >  	unsigned int *val, unsigned int size);
> > > >  
> > > > +/**
> > > > + * __adis_write_reg_8() - Write single byte to a register
> > > > (unlocked
> > > > version)
> > > > + * @adis: The adis device
> > > > + * @reg: The address of the register to be written
> > > > + * @value: The value to write
> > > > + */
> > > > +static inline int __adis_write_reg_8(struct adis *adis, unsigned
> > > > int
> > > > reg,
> > > > +	uint8_t val)
> > > > +{
> > > > +	return __adis_write_reg(adis, reg, val, 1);
> > > > +}
> > > > +
> > > > +/**
> > > > + * __adis_write_reg_16() - Write 2 bytes to a pair of registers
> > > > (unlocked version)
> > > > + * @adis: The adis device
> > > > + * @reg: The address of the lower of the two registers
> > > > + * @value: Value to be written
> > > > + */
> > > > +static inline int __adis_write_reg_16(struct adis *adis, unsigned
> > > > int reg,
> > > > +	uint16_t val)
> > > > +{
> > > > +	return __adis_write_reg(adis, reg, val, 2);
> > > > +}
> > > > +
> > > > +/**
> > > > + * __adis_write_reg_32() - write 4 bytes to four registers
> > > > (unlocked
> > > > version)
> > > > + * @adis: The adis device
> > > > + * @reg: The address of the lower of the four register
> > > > + * @value: Value to be written
> > > > + */
> > > > +static inline int __adis_write_reg_32(struct adis *adis, unsigned
> > > > int reg,
> > > > +	uint32_t val)
> > > > +{
> > > > +	return __adis_write_reg(adis, reg, val, 4);
> > > > +}
> > > > +
> > > > +/**
> > > > + * __adis_read_reg_16() - read 2 bytes from a 16-bit register
> > > > (unlocked version)
> > > > + * @adis: The adis device
> > > > + * @reg: The address of the lower of the two registers
> > > > + * @val: The value read back from the device
> > > > + */
> > > > +static inline int __adis_read_reg_16(struct adis *adis, unsigned
> > > > int
> > > > reg,
> > > > +	uint16_t *val)
> > > > +{
> > > > +	unsigned int tmp;
> > > > +	int ret;
> > > > +
> > > > +	ret = __adis_read_reg(adis, reg, &tmp, 2);
> > Zero day isn't happy that this can use tmp without it actually being
> > set
> > in the
> > __adis_read_reg.
> > 
> > I've added
> > 	if (ret)
> > 		return ret;
> > > > +	*val = tmp;
> > > > +
> > > > +	return ret;
> > and changed this to return 0;
> > 
> > Same in the 32bit case below.
> > 
> > Hmm. There are quite a few sparse warnings in the adis16400 if anyone
> > fancies
> > cleaning them up ;)
> 
> Well, I've been planning to setup sparse as part of our CI.
> I guess this is another nudge in that direction.

I did find some warnings.
But they seem to be reported by GCC 8.
Not sure if GCC 7 reported them.
I re-installed my laptop [changed to another one], so maybe my default is
now 8; or maybe I did not notice this initially when I built it and picked
it up from our master branch.

Sparse reports nothing for the IMU drivers.
Should I try something newer?

sparse --version
0.6.0 (Ubuntu: 0.6.0-3)

-----------------------------------------------------------------
ARCH=arm CROSS_COMPILE=~/work/linux/gcc-linaro-5.5.0-2017.10-x86_64_arm-
linux-gnueabi/bin/arm-linux-gnueabi- make C=2 drivers/iio/imu/
  CHECK   scripts/mod/empty.c
  CALL    scripts/checksyscalls.sh
  CALL    scripts/atomic/check-atomics.sh
  CHECK   drivers/iio/imu/adis16400.c
  CHECK   drivers/iio/imu/adis16460.c
  CHECK   drivers/iio/imu/adis16480.c
  CHECK   drivers/iio/imu/adis.c
  CHECK   drivers/iio/imu/adis_trigger.c
  CHECK   drivers/iio/imu/adis_buffer.c
-----------------------------------------------------------------

> 
> Thanks
> Alex
> 
> > Thanks,
> > 
> > Jonathan
> > 
> > > > +}
> > > > +
> > > > +/**
> > > > + * __adis_read_reg_32() - read 4 bytes from a 32-bit register
> > > > (unlocked version)
> > > > + * @adis: The adis device
> > > > + * @reg: The address of the lower of the two registers
> > > > + * @val: The value read back from the device
> > > > + */
> > > > +static inline int __adis_read_reg_32(struct adis *adis, unsigned
> > > > int
> > > > reg,
> > > > +	uint32_t *val)
> > > > +{
> > > > +	unsigned int tmp;
> > > > +	int ret;
> > > > +
> > > > +	ret = __adis_read_reg(adis, reg, &tmp, 4);
> > > > +	*val = tmp;
> > > > +
> > > > +	return ret;
> > > > +}
> > > > +
> > > > +/**
> > > > + * adis_write_reg() - write N bytes to register
> > > > + * @adis: The adis device
> > > > + * @reg: The address of the lower of the two registers
> > > > + * @value: The value to write to device (up to 4 bytes)
> > > > + * @size: The size of the @value (in bytes)
> > > > + */
> > > > +static inline int adis_write_reg(struct adis *adis, unsigned int
> > > > reg,
> > > > +	unsigned int val, unsigned int size)
> > > > +{
> > > > +	int ret;
> > > > +
> > > > +	mutex_lock(&adis->state_lock);
> > > > +	ret = __adis_write_reg(adis, reg, val, size);
> > > > +	mutex_unlock(&adis->state_lock);
> > > > +
> > > > +	return ret;
> > > > +}
> > > > +
> > > > +/**
> > > > + * adis_read_reg() - read N bytes from register
> > > > + * @adis: The adis device
> > > > + * @reg: The address of the lower of the two registers
> > > > + * @val: The value read back from the device
> > > > + * @size: The size of the @val buffer
> > > > + */
> > > > +static int adis_read_reg(struct adis *adis, unsigned int reg,
> > > > +	unsigned int *val, unsigned int size)
> > > > +{
> > > > +	int ret;
> > > > +
> > > > +	mutex_lock(&adis->state_lock);
> > > > +	ret = __adis_read_reg(adis, reg, val, size);
> > > > +	mutex_unlock(&adis->state_lock);
> > > > +
> > > > +	return ret;
> > > > +}
> > > > +
> > > >  /**
> > > >   * adis_write_reg_8() - Write single byte to a register
> > > >   * @adis: The adis device