Hi, On Tue, Oct 17, 2017 at 02:40:31PM +0200, Thierry Reding wrote: > On Tue, Oct 17, 2017 at 06:16:23PM +0800, Jeffy Chen wrote: > > When the pwm driver is unbound while the pwm is still requested, the > > pwm core would not actually remove the pwmchip(return -EBUSY instead). > > > > So it would hold some references to the invalid resources(e.g. pwmchip). > > > > And the customer who requested the pwm would have those references too, > > and may crash the kernel when trying to access them later. > > > > Add a dummy pwmchip, and assign orphan pwms to it to avoid that. > > > > Signed-off-by: Jeffy Chen <jeffy.c...@rock-chips.com> > > --- > > > > Changes in v4: > > Fix compile warning. > > > > Changes in v3: > > Assign orphan pwms to dummy pwmchip instead of adding device link in the > > customer driver. > > What happened to this? Device links were specifically designed to avoid > situations like these.
I think Jeffy came up with this as an odd response to my suggestion on v2 that we could just handle the device links in the PWM core. I don't fully understand why the complete change in direction... BTW, since you seem to have an opinion about device links: is it expected that all consumer drivers will make explicit calls to device_link_add()? I thought this should be avoided, if possible (e.g., this can be handled in pwm_get()). > A dummy PWM chip doesn't seem like the right solution to this. Agreed. Brian
