On Thu, 1 Sep 2016 10:29:37 -0500 Reza Arbab <arbab@xxxxxxxxxxxxxxxxxx> wrote:
> If store_mem_state() is called to online memory which is already online,
> it will return 1, the value it got from device_online().
>
> This is wrong because store_mem_state() is a device_attribute .store
> function. Thus a non-negative return value represents input bytes read.
>
> Set the return value to -EINVAL in this case.
>
I actually made the mistake of reading this code.
What the heck are the return value semantics of bus_type.online?
Sometimes 0, sometimes 1 and apparently sometimes -Efoo values. What
are these things trying to tell the caller and why is "1" ever useful
and why doesn't anyone document anything. grr.
And now I don't understand this patch. Because:
static int memory_subsys_online(struct device *dev)
{
struct memory_block *mem = to_memory_block(dev);
int ret;
if (mem->state == MEM_ONLINE)
return 0;
Doesn't that "return 0" contradict the changelog?
Also, is store_mem_state() the correct place to fix this? Instead,
should memory_block_change_state() detect an attempt to online
already-online memory and itself return -EINVAL, and permit that to be
propagated back? Well, that depends on the bus_type.online rules which
appear to be undocumented. What is the bus implementation supposed to
do when a request is made to online an already-online device?
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