Matt Brown <matthew.brown....@gmail.com> writes:
> On Sat, Aug 5, 2017 at 3:06 AM, Tyrel Datwyler <tyr...@linux.vnet.ibm.com>
> wrote:
>> On 08/03/2017 06:12 PM, Matt Brown wrote:
>>> @@ -135,8 +152,9 @@ static __init int rng_create(struct device_node *dn)
>>>
>>> static __init int rng_init(void)
>>> {
>>> + unsigned long darn_test;
>>> struct device_node *dn;
>>> - int rc;
>>> + int rc, i;
>>>
>>> for_each_compatible_node(dn, NULL, "ibm,power-rng") {
>>> rc = rng_create(dn);
>>> @@ -150,6 +168,21 @@ static __init int rng_init(void)
>>> of_platform_device_create(dn, NULL, NULL);
>>> }
>>>
>>> + if (cpu_has_feature(CPU_FTR_ARCH_300)) {
>>> + for (i = 0; i < 10; i++) {
>>> + if (powernv_get_random_darn(&darn_test)) {
>>> + ppc_md.get_random_seed =
>>> + powernv_get_random_darn;
>>> + break;
>>
>> If you return directly here you can avoid the (i == 9) conditional every
>> iteration of the
>> loop by moving the pr_warn to just outside the loop.
>
> That's true, although it is very unlikely for the
> powernv_get_random_darn to fail. So in practice we should never reach
> the (i == 9) conditional.
> The loop is more of a backup in the rare case that it does fail.
All true, the runtime overhead is really not an issue. It's more that
testing for loop almost-termination in the loop is a bit gross :)
I think the best solution is to just pull it out into a separate
function, it also avoids adding sometimes unused variables to the outer
function, eg:
static int initialise_darn(void)
{
unsigned long val;
if (!cpu_has_feature(CPU_FTR_ARCH_300))
return -ENODEV;
for (i = 0; i < 10; i++) {
if (powernv_get_random_darn(&val)) {
ppc_md.get_random_seed = powernv_get_random_darn;
return 0;
}
}
return -EIO;
}
cheers
