On Fri, Sep 18, 2020 at 08:45:52PM +0800, Alexander Shishkin wrote: > Tingwei Zhang <ting...@codeaurora.org> writes: > > > @@ -63,6 +65,7 @@ static int __init stm_ftrace_init(void) > > { > > int ret; > > > > + stm_ftrace.data.nr_chans = num_possible_cpus(); > > Not a problem with this patch necesarily, but this made me realize that > .nr_chans may be larger than: > > (1) what the policy permits, > (2) what the stm device can handle. > > While (1) the user can fix in the policy, they won't be able to fix (2), > in which case they won't be able to use stm_ftrace at all. I'm thinking > if a link-time callback would be good enough. >
Hi Alex, I'm not sure if I understand this correct. If the nr_chans requested by stm_ftrace is larger than policy permits or stm device can handle, stm_assign_first_policy() returns with error so stm_source_link_add() will fail. User would notice that when link happens. There's not much we can do if resource is not enough. > Another thing is that .nr_chans needs to be a power of 2 at the moment. > I'll change to below. stm_ftrace.data.nr_chans = roundup_pow_of_two(num_possible_cpus()); > Regards, > -- > Alex > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-ker...@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel