Re: [PATCH v2 1/8] staging:iio:ade7854: Fix error handling on read/write

[Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>]

On 03/18, Jonathan Cameron wrote:
> On Fri, 16 Mar 2018 19:48:33 -0300
> Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com> wrote:
> 
> > The original code does not correctly handle the error related to I2C
> > read and write. This patch fixes the error handling related to all
> > read/write functions for I2C. This patch is an adaptation of the John
> > Syne patches.
> > 
> > Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
> > Signed-off-by: John Syne <john3909@gmail.com>
> Hi Rodrigo,
> 
> I'm not sure what the chain of authorship was here.  If this is fundamentally
> John's original patch he should still be the author and his sign off should be
> first.  You then sign off afterwards to indicate that you 'handled' the patch
> and believe the work to be John's (you are trusting his sign off).  This
> is 'fun' legal stuff - read the docs on developers certificate of origin.
> 
> If the patch has changed 'enough' (where that is a fuzzy definition)
> then you should as you have here take the authorship, but John's sign off is
> no longer true (it's a different patch).  If John has reviewed the code
> it is fine to have a reviewed-by or acked-by from John there to reflect
> that.
> 
> Anyhow, please clarify the situation as I shouldn't take a patch where
> I'm applying my sign-off without knowing the origins etc.

Hi Jonathan,

Just for clarification, this is fundamentally John's original patch with
some changes on the way that write_reg operation returns the error. I
should ask for someone else, how to correctly handle this situation
since I did not have experience with this situation.

Actually, when I worked on this patch, I was confused about using
different authorship from the email. I got confused because of the
following statement:

"Make sure that the email you specify here is the same email you used to
set up sending mail. The Linux kernel developers will not accept a patch
where the "From" email differs from the "Signed-off-by" line, which is
what will happen if these two emails do not match." [1]

Anyway, I think this is not a newbie issue, and I should asked first.
Thanks for the great explanation, I will not make this kind of mistake
again.

Thanks

[1] - https://kernelnewbies.org/FirstKernelPatch
 
> > ---
> >  drivers/staging/iio/meter/ade7854-i2c.c | 24 ++++++++++++------------
> >  drivers/staging/iio/meter/ade7854.c     | 10 +++++-----
> >  2 files changed, 17 insertions(+), 17 deletions(-)
> > 
> > diff --git a/drivers/staging/iio/meter/ade7854-i2c.c b/drivers/staging/iio/meter/ade7854-i2c.c
> > index 317e4f0d8176..4437f1e33261 100644
> > --- a/drivers/staging/iio/meter/ade7854-i2c.c
> > +++ b/drivers/staging/iio/meter/ade7854-i2c.c
> > @@ -31,7 +31,7 @@ static int ade7854_i2c_write_reg_8(struct device *dev,
> >  	ret = i2c_master_send(st->i2c, st->tx, 3);
> >  	mutex_unlock(&st->buf_lock);
> >  
> > -	return ret;
> > +	return ret < 0 ? ret : 0;
> >  }
> >  
> >  static int ade7854_i2c_write_reg_16(struct device *dev,
> > @@ -51,7 +51,7 @@ static int ade7854_i2c_write_reg_16(struct device *dev,
> >  	ret = i2c_master_send(st->i2c, st->tx, 4);
> >  	mutex_unlock(&st->buf_lock);
> >  
> > -	return ret;
> > +	return ret < 0 ? ret : 0;
> >  }
> >  
> >  static int ade7854_i2c_write_reg_24(struct device *dev,
> > @@ -72,7 +72,7 @@ static int ade7854_i2c_write_reg_24(struct device *dev,
> >  	ret = i2c_master_send(st->i2c, st->tx, 5);
> >  	mutex_unlock(&st->buf_lock);
> >  
> > -	return ret;
> > +	return ret < 0 ? ret : 0;
> >  }
> >  
> >  static int ade7854_i2c_write_reg_32(struct device *dev,
> > @@ -94,7 +94,7 @@ static int ade7854_i2c_write_reg_32(struct device *dev,
> >  	ret = i2c_master_send(st->i2c, st->tx, 6);
> >  	mutex_unlock(&st->buf_lock);
> >  
> > -	return ret;
> > +	return ret < 0 ? ret : 0;
> >  }
> So for write cases you are flattening to 0 for good and < 0 for bad.
> good.
> >  
> >  static int ade7854_i2c_read_reg_8(struct device *dev,
> > @@ -110,11 +110,11 @@ static int ade7854_i2c_read_reg_8(struct device *dev,
> >  	st->tx[1] = reg_address & 0xFF;
> >  
> >  	ret = i2c_master_send(st->i2c, st->tx, 2);
> > -	if (ret)
> > +	if (ret < 0)
> >  		goto out;
> >  
> >  	ret = i2c_master_recv(st->i2c, st->rx, 1);
> > -	if (ret)
> > +	if (ret < 0)
> >  		goto out;
> >  
> >  	*val = st->rx[0];
> But in read cases you are returning the number of bytes read...
> Given these functions can know the 'right' answer to that why not check
> it here and do the same as for writes in return 0 for good and < 0 for
> bad?
> > @@ -136,11 +136,11 @@ static int ade7854_i2c_read_reg_16(struct device *dev,
> >  	st->tx[1] = reg_address & 0xFF;
> >  
> >  	ret = i2c_master_send(st->i2c, st->tx, 2);
> > -	if (ret)
> > +	if (ret < 0)
> >  		goto out;
> >  
> >  	ret = i2c_master_recv(st->i2c, st->rx, 2);
> > -	if (ret)
> > +	if (ret < 0)
> >  		goto out;
> >  
> >  	*val = (st->rx[0] << 8) | st->rx[1];
> > @@ -162,11 +162,11 @@ static int ade7854_i2c_read_reg_24(struct device *dev,
> >  	st->tx[1] = reg_address & 0xFF;
> >  
> >  	ret = i2c_master_send(st->i2c, st->tx, 2);
> > -	if (ret)
> > +	if (ret < 0)
> >  		goto out;
> >  
> >  	ret = i2c_master_recv(st->i2c, st->rx, 3);
> > -	if (ret)
> > +	if (ret < 0)
> >  		goto out;
> >  
> >  	*val = (st->rx[0] << 16) | (st->rx[1] << 8) | st->rx[2];
> > @@ -188,11 +188,11 @@ static int ade7854_i2c_read_reg_32(struct device *dev,
> >  	st->tx[1] = reg_address & 0xFF;
> >  
> >  	ret = i2c_master_send(st->i2c, st->tx, 2);
> > -	if (ret)
> > +	if (ret < 0)
> >  		goto out;
> >  
> >  	ret = i2c_master_recv(st->i2c, st->rx, 3);
> > -	if (ret)
> > +	if (ret < 0)
> >  		goto out;
> >  
> >  	*val = (st->rx[0] << 24) | (st->rx[1] << 16) |
> > diff --git a/drivers/staging/iio/meter/ade7854.c b/drivers/staging/iio/meter/ade7854.c
> > index 90d07cdca4b8..0193ae3aae29 100644
> > --- a/drivers/staging/iio/meter/ade7854.c
> > +++ b/drivers/staging/iio/meter/ade7854.c
> > @@ -33,7 +33,7 @@ static ssize_t ade7854_read_8bit(struct device *dev,
> >  	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
> >  
> >  	ret = st->read_reg_8(dev, this_attr->address, &val);
> > -	if (ret)
> > +	if (ret < 0)
> If you did as discussed above with the reads then this change would not
> be needed and all the changes would be confined to the i2c code.
> 
> Thanks,
> 
> Jonathan
> 
> 
> >  		return ret;
> >  
> >  	return sprintf(buf, "%u\n", val);
> > @@ -50,7 +50,7 @@ static ssize_t ade7854_read_16bit(struct device *dev,
> >  	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
> >  
> >  	ret = st->read_reg_16(dev, this_attr->address, &val);
> > -	if (ret)
> > +	if (ret < 0)
> >  		return ret;
> >  
> >  	return sprintf(buf, "%u\n", val);
> > @@ -67,7 +67,7 @@ static ssize_t ade7854_read_24bit(struct device *dev,
> >  	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
> >  
> >  	ret = st->read_reg_24(dev, this_attr->address, &val);
> > -	if (ret)
> > +	if (ret < 0)
> >  		return ret;
> >  
> >  	return sprintf(buf, "%u\n", val);
> > @@ -84,7 +84,7 @@ static ssize_t ade7854_read_32bit(struct device *dev,
> >  	struct ade7854_state *st = iio_priv(indio_dev);
> >  
> >  	ret = st->read_reg_32(dev, this_attr->address, &val);
> > -	if (ret)
> > +	if (ret < 0)
> >  		return ret;
> >  
> >  	return sprintf(buf, "%u\n", val);
> > @@ -416,7 +416,7 @@ static int ade7854_set_irq(struct device *dev, bool enable)
> >  	u32 irqen;
> >  
> >  	ret = st->read_reg_32(dev, ADE7854_MASK0, &irqen);
> > -	if (ret)
> > +	if (ret < 0)
> >  		return ret;
> >  
> >  	if (enable)
>