On Thu, Dec 20, 2018 at 07:12:55PM +0530, Buland Singh wrote: > On 12/20/18 5:59 PM, Greg KH wrote: > > On Thu, Dec 20, 2018 at 05:35:24PM +0530, Buland Singh wrote: > > > Commit '3d035f580699 ("drivers/char/hpet.c: allow user controlled mmap for > > > user processes")' introduced a new kernel command line parameter > > > hpet_mmap, > > > that is required to expose the memory map of the HPET registers to > > > user-space. Unfortunately the kernel command line parameter 'hpet_mmap' is > > > broken and never takes effect due to missing '=' character in the > > > __setup() > > > code of hpet_mmap_enable. > > > > > > Before this patch: > > > > > > dmesg output with the kernel command line parameter hpet_mmap=1 > > > > > > [ 0.204152] HPET mmap disabled > > > > > > dmesg output with the kernel command line parameter hpet_mmap=0 > > > > > > [ 0.204192] HPET mmap disabled > > > > > > After this patch: > > > > > > dmesg output with the kernel command line parameter hpet_mmap=1 > > > > > > [ 0.203945] HPET mmap enabled > > > > > > dmesg output with the kernel command line parameter hpet_mmap=0 > > > > > > [ 0.204652] HPET mmap disabled > > > > > > Fixes: 3d035f580699 ("drivers/char/hpet.c: allow user controlled mmap for > > > user processes") > > > Signed-off-by: Buland Singh <bsi...@redhat.com> > > > --- > > > drivers/char/hpet.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/drivers/char/hpet.c b/drivers/char/hpet.c > > > index 4a22b4b41aef..9bffcd37cc7b 100644 > > > --- a/drivers/char/hpet.c > > > +++ b/drivers/char/hpet.c > > > @@ -377,7 +377,7 @@ static __init int hpet_mmap_enable(char *str) > > > pr_info("HPET mmap %s\n", hpet_mmap_enabled ? "enabled" : > > > "disabled"); > > > return 1; > > > } > > > -__setup("hpet_mmap", hpet_mmap_enable); > > > +__setup("hpet_mmap=", hpet_mmap_enable); > > Hello Greag, > > > This has _never_ worked? Since 3.13? > > Yes, that's true :) > > > Why not just remove the thing as it is obvious no one actually has ever > > used it. > That would make the code even simpler :) > > Data Plane Development Kit (DPDK)[1] provides API that requires the > CONFIG_HPET_MMAP > kernel configuration option to be enabled[2]. Some end users might want to > use the > HPET MMAP functionality within the application.
But, obviously, they really don't need to do that from the kernel command line as no one has ever noticed this didn't work :) Also, that page: > [2] https://doc.dpdk.org/guides-18.08/linux_gsg/enable_func.html Does not say to use this command line option either. So if no one has ever used it, please, let us just delete it. thanks, greg k-h