On Sun, Feb 02, 2014 at 06:30:00PM +0100, Jean-Francois Moine wrote:
On Sun, 2 Feb 2014 16:20:58 +0000 Russell King - ARM Linux linux@arm.linux.org.uk wrote:
On Sat, Jan 25, 2014 at 06:14:45PM +0100, Jean-Francois Moine wrote:
This patch adds more error checking inn I2C I/O functions. In case of I/O error, this permits to avoid writing in bad controller pages, a bad chipset detection or looping when getting the EDID.
I've just looked at this again, and spotted something:
-static uint8_t +static int reg_read(struct tda998x_priv *priv, uint16_t reg) { uint8_t val = 0;
- reg_read_range(priv, reg, &val, sizeof(val));
- int ret;
- ret = reg_read_range(priv, reg, &val, sizeof(val));
- if (ret < 0)
return ret;So yes, this can return negative numbers.
@@ -1158,8 +1184,11 @@ tda998x_encoder_init(struct i2c_client *client, tda998x_reset(priv);
/* read version: */
- priv->rev = reg_read(priv, REG_VERSION_LSB) |
reg_read(priv, REG_VERSION_MSB) << 8;
- ret = reg_read(priv, REG_VERSION_LSB) |
(reg_read(priv, REG_VERSION_MSB) << 8);- if (ret < 0)
goto fail;- priv->rev = ret;
Two issues here:
- The additional parens are /really/ not required.
- What if reg_read(priv, REG_VERSION_MSB) returns a negative number?
If we're going to the extent of attempting to make the read/write functions return errors, we should at least handle errors generated by them properly, otherwise it's pointless making them return errors.
ret = reg_read(priv, REG_VERSION_LSB); if (ret < 0) goto fail;
priv->rev = ret;
ret = reg_read(priv, REG_VERSION_MSB); if (ret < 0) goto fail;
priv->rev |= ret << 8;
If you want it to look slightly nicer:
int rev_lo, rev_hi;
rev_lo = reg_read(priv, REG_VERSION_LSB); rev_hi = reg_read(priv, REG_VERSION_MSB); if (rev_lo < 0 || rev_hi < 0) { ret = rev_lo < 0 ? rev_lo : rev_hi; goto fail; }
priv->rev = rev_lo | rev_hi << 8;
I'm happy to commit such a change after this patch to clean it up, or if you want to regenerate your patch 2 and post /just/ that incorporating this change.
I think that my code works correctly: when there is an error, the result of reg_read() is minus the error code, and this error code is always lower than 8388607 (0x7fffff). Then, reg_read() << 8 will always be negative.
The issue I'm pointing out is not whether it will be interpreted as an error or not, it's whether the value is a correct error code. If we don't care about the reason why an error occurs, we might as well just return -1.
I've added my own patch which adjusts it as per above to my tree anyway, so I'm not that worried about this.