On Mon, Jan 25, 2016 at 06:07:32PM +0100, Arnd Bergmann wrote:
gcc warns about the possibilty of accessing a property read from devicetree in cs35l32_i2c_probe() when it has not been initialized because CONFIG_OF is disabled:
sound/soc/codecs/cs35l32.c: In function 'cs35l32_i2c_probe': sound/soc/codecs/cs35l32.c:278:2: warning: 'val' may be used uninitialized in this function [-Wmaybe-uninitialized]
The code is actually correct because it checks the dev->of_node variable first and we know this is NULL here, but by adding a check for IS_ENABLED(CONFIG_OF), we can let the compiler know as well, and also generate smaller object code.
No, the code is buggy, and the compiler is very correct in warning about it.
The code there is:
of_property_read_u32(np, "cirrus,boost-manager", &val); switch (val) {
of_property_read_u32() is aliased to of_property_read_u32_array() via:
static inline int of_property_read_u32(const struct device_node *np, const char *propname, u32 *out_value) { return of_property_read_u32_array(np, propname, out_value, 1); }
which does this:
int of_property_read_u32_array(const struct device_node *np, const char *propname, u32 *out_values, size_t sz) { const __be32 *val = of_find_property_value_of_size(np, propname, (sz * sizeof(*out_values)));
if (IS_ERR(val)) return PTR_ERR(val);
while (sz--) *out_values++ = be32_to_cpup(val++); return 0; }
Note that 'out_values' is not written to if of_find_property_value_of_size() returns an error. Therefore, if cirrus,boost-manager is missing, the resulting value of 'val' is left uninitialised.