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

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

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.

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