2016-05-23 22:35 GMT+02:00 Arnd Bergmann <arnd@xxxxxxxx>: > On Monday, May 23, 2016 6:14:08 PM CEST Sudip Mukherjee wrote: >> We have been getting build warning about: >> drivers/char/hw_random/stm32-rng.c: In function 'stm32_rng_read': >> drivers/char/hw_random/stm32-rng.c:82:19: warning: 'sr' may be used >> uninitialized in this function >> >> On checking the code it turns out that sr can never be used >> uninitialized as sr is getting initialized in the while loop and while >> loop will always execute as the minimum value of max can be 32. >> So just initialize sr to 0 while declaring it to silence the compiler. >> >> Signed-off-by: Sudip Mukherjee <sudip.mukherjee@xxxxxxxxxxxxxxx> >> --- > > I notice that you are using a really old compiler. While this warning > seems to be valid in the sense that the compiler should figure out that > the variable might be used uninitialized, please update your toolchain > before reporting other such problems, as gcc-4.6 had a lot more false > positives that newer ones (5.x or 6.x) have. > >> >> build log at: >> https://travis-ci.org/sudipm-mukherjee/parport/jobs/132180906 >> >> drivers/char/hw_random/stm32-rng.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/char/hw_random/stm32-rng.c b/drivers/char/hw_random/stm32-rng.c >> index 92a8106..0533370 100644 >> --- a/drivers/char/hw_random/stm32-rng.c >> +++ b/drivers/char/hw_random/stm32-rng.c >> @@ -52,7 +52,7 @@ static int stm32_rng_read(struct hwrng *rng, void *data, size_t max, bool wait) >> { >> struct stm32_rng_private *priv = >> container_of(rng, struct stm32_rng_private, rng); >> - u32 sr; >> + u32 sr = 0; >> int retval = 0; >> >> pm_runtime_get_sync((struct device *) priv->rng.priv); > > Does this work as well? > > diff --git a/drivers/char/hw_random/stm32-rng.c b/drivers/char/hw_random/stm32-rng.c > index 92a810648bd0..5c836b0afa40 100644 > --- a/drivers/char/hw_random/stm32-rng.c > +++ b/drivers/char/hw_random/stm32-rng.c > @@ -79,7 +79,7 @@ static int stm32_rng_read(struct hwrng *rng, void *data, size_t max, bool wait) > max -= sizeof(u32); > } > > - if (WARN_ONCE(sr & (RNG_SR_SEIS | RNG_SR_CEIS), > + if (WARN_ONCE(retval > 0 && (sr & (RNG_SR_SEIS | RNG_SR_CEIS)), > "bad RNG status - %x\n", sr)) > writel_relaxed(0, priv->base + RNG_SR); > > I think it would be nicer to not add a bogus initialization. Hmm, no sure this nicer. The while loop can break before retval is incremented when sr value is not expected (sr != RNG_SR_DRDY). In that case, we certainly want to print sr value. Maybe the better way is just to initialize sr with status register content? diff --git a/drivers/char/hw_random/stm32-rng.c b/drivers/char/hw_random/stm32-rng.c index 92a810648bd0..07a6659d0fe6 100644 --- a/drivers/char/hw_random/stm32-rng.c +++ b/drivers/char/hw_random/stm32-rng.c @@ -57,8 +57,8 @@ static int stm32_rng_read(struct hwrng *rng, void *data, size_t max, bool wait) pm_runtime_get_sync((struct device *) priv->rng.priv); + sr = readl_relaxed(priv->base + RNG_SR); while (max > sizeof(u32)) { - sr = readl_relaxed(priv->base + RNG_SR); if (!sr && wait) { unsigned int timeout = RNG_TIMEOUT; @@ -77,6 +77,8 @@ static int stm32_rng_read(struct hwrng *rng, void *data, size_t max, bool wait) retval += sizeof(u32); data += sizeof(u32); max -= sizeof(u32); + + sr = readl_relaxed(priv->base + RNG_SR); } if (WARN_ONCE(sr & (RNG_SR_SEIS | RNG_SR_CEIS), Regards, Maxime -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
