On 12 August 2016 at 11:57, Vince Weaver <vince@xxxxxxxxxx> wrote: > On Thu, 11 Aug 2016, Mathieu Poirier wrote: >> +.TP >> +.BR PERF_EVENT_IOC_SET_DRV_CONFIGS " (since Linux 4.9)" >> +This makes it possible to pass configuration parameters to PMU drivers. >> +Configuration parameters are specific to each drivers. >> + >> +The argument is a pointer to the desired configuration parameters. > > So I gave up and read the code and I'm guessing this is what you really > mean: > > .TP > .BR PERF_EVENT_IOC_SET_DRV_CONFIGS " (since Linux 4.9)" > Pass custom configuration paramaters to a PMU driver. > > The argument is a pointer to a NUL-termiated string of up to > PAGE_SIZE in length. > The string contains a list of comma-separated configuration options > that will be parsed by the kernel. > The kernel handles both singleton values as well as name/value pairs > that are indicated with the '=' character. > The size of the strings is limited internally to PERF_DRV_CONFIG_MAX > (which is not visible to userspace). > Yes this is a very good description but in sharp contrast with what is currently done for the ioctl() descriptors in this page. I shied away from writing that much based on how slim the current descriptions were. > > > some additional questions: can this ioctl be run at any time or should it > only be run while the event is quiet? Does the change in options take > place immediately? That is up to PMU drivers to decide - for CoreSight it is set only once when trace sessions are created. Any changes from thereon will be ignored. Thanks for the review. Mathieu > > Vince -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
