> > Smatch finds this code hard to parse. It says that "count" is a user
> > controlled number between 0-u64max which has an upperbound (but the
> > upper bound is variable instead of a constant).
> >
> > Can count actually be zero? Smatch is normally good at tracking that...
>
> 'count' is the total number of bytes in i2c frame: it takes into account
> the number of bytes for address ('reg_bits / 8') + the number of bytes
> for data (which is at least 'val_bits / 8')
> So, with 'reg_bits = 16' and 'val_bits = 8' in 'tps6594_i2c_regmap_config'
> struct, 'count' should be at least 3. It cannot be zero.
Gar... You're right. I see that now in _regmap_raw_write_impl().
drivers/base/regmap/regmap.c
1846 /* If we're doing a single register write we can probably just
1847 * send the work_buf directly, otherwise try to do a gather
1848 * write.
1849 */
1850 if (val == work_val)
1851 ret = map->write(map->bus_context, map->work_buf,
1852 map->format.reg_bytes +
1853 map->format.pad_bytes +
1854 val_len);
1855 else if (map->bus && map->bus->gather_write)
1856 ret = map->bus->gather_write(map->bus_context, map->work_buf,
1857 map->format.reg_bytes +
1858 map->format.pad_bytes,
1859 val, val_len);
1860 else
1861 ret = -ENOTSUPP;
1862
My mind only saw "val_len is the last parameter" and I missed the
"map->format.reg_bytes + map->format.pad_bytes + " on the lines before.
> Special handling for 'count == 1' (or 'count < 2') makes sense indeed.
>
> I'm not sure that I fully understand, though. Will Smatch stop complaining
> for both things that you mentioned above with a patch for handling 'count < 2' ?
> Or will we consider either that warnings are handled, even if they are still there.
No, don't do anything to silence the warning. Always fix the checker
instead of working around it.
Handling the "map->format.reg_bytes + map->format.pad_bytes + val_len"
is kind of complicated but still easier than handling the:
if (val_len % map->format.val_bytes)
condition in regmap_raw_write() just because it's closer together. It's
quite a bit of code to write to silence this false positive but it's
something which could be done.
regards,
dan carpenter
