Messages in this thread | | | Subject | Re: [PATCH 3/5] powerpc/ftw: Implement a simple FTW driver | From | Randy Dunlap <> | Date | Wed, 17 Jan 2018 10:30:37 -0800 |
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On 01/16/18 18:50, Sukadev Bhattiprolu wrote: > The Fast Thread Wake-up (FTW) driver provides user space applications an > interface to the low latency Core-to-Core wakeup functionality in POWER9. > > This mechanism allows a thread on one core to efficiently send a message > to a "waiting thread" on another core on the same chip, using the Virtual > Accelrator Switchboard (VAS) subsystem. > > This initial FTW driver implements the ioctl and mmap operations on an > FTW device node. Using these operations, a pair of application threads > can establish a "communication channel" and use the COPY, PASTE and WAIT > instructions to wait/wake up. > > PATCH 5/5 documents the API and includes an example of the usage. > > Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> > --- > Changelog[v2] > - [Michael Neuling] Rename from drop "nx" from name "nx-ftw". > - [Michael Neuling] Use a single VAS_FTW_SETUP ioctl to simplify > interface. > - [Michael Ellerman] To work with paste emulation patch, mark > PTE dirty in ->mmap() to ensure there is no fault on paste > (the emulation patch must disable pagefaults when updating > thread reconfig registers). > - Check return value from set_thread_tidr(). > - Move driver drivers/misc/ftw. > > --- > drivers/misc/Kconfig | 1 + > drivers/misc/Makefile | 1 + > drivers/misc/ftw/Kconfig | 16 +++ > drivers/misc/ftw/Makefile | 4 + > drivers/misc/ftw/ftw.c | 346 ++++++++++++++++++++++++++++++++++++++++++++++ > 5 files changed, 368 insertions(+) > create mode 100644 drivers/misc/ftw/Kconfig > create mode 100644 drivers/misc/ftw/Makefile > create mode 100644 drivers/misc/ftw/ftw.c
> +static long ftw_ioctl(struct file *fp, unsigned int cmd, unsigned long arg) > +{ > + switch (cmd) { > + > + case FTW_SETUP: > + return ftw_ioc_ftw_setup(fp, arg); > + > + default: > + return -EINVAL; > + } > +}
Nit: some versions of gcc (or maybe clang) complain about a typed function not always having a return value in code like above, so it is often done as:
> +static long ftw_ioctl(struct file *fp, unsigned int cmd, unsigned long arg) > +{ > + switch (cmd) { > + > + case FTW_SETUP: > + return ftw_ioc_ftw_setup(fp, arg); > + > + default: > + break; > + }
return -EINVAL; > +}
Do you expect to implement more ioctls? If not, just change the switch to an if ().
-- ~Randy
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