On Wed, Apr 01, 2015 at 11:58:50AM +0530, Shobhit Kumar wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On 03/24/2015 01:53 PM, Thierry Reding wrote: > > On Fri, Mar 13, 2015 at 07:28:02PM +0530, Shobhit Kumar wrote: > >> Some chips instead of using period_ns and duty_ns can be > >> configured using the clock divisor and duty percent. Adds an > >> alternative configuration method for such chips > > > > I don't see a need to introduce this alternative configuration > > mechanism. Most, of not all, of the other drivers program a clock > > divisor and some percentage of the duty cycle as well and it should > > be easy to convert to that internally from the period and > > duty_cycle parameters that you get in ->config(). > > Perhaps. Probably I misunderstood but as per Documentation/pwm.txt, it > is suggested that rather than calculating in the driver, we can add > additional helpers. So I tried doing just that. And it also means that > the consumer(which is directly aware of the percent it wants) has to > do the calculation and pass as ns values and we internally again > convert back to percentage ? Yes. The interface assumes that you'll pass in absolute values for the period and duty cycle. Existing drivers, such as pwm-backlight, already convert a percentage or other internal representation to these absolute values. If your driver internally works with percent you can easily convert to that from the absolute values. The documentation only makes a suggestion. I think it'd be fine if you kept this conversion internal to the driver. We can turn it into a more generic helper if a second driver appears that needs the same conversion. > > Adding an alternative means of configuring the PWM also means that > > every user driver now potentially needs to support both the > > traditional and the alternative way because PWM providers may not > > implement both. > > I just assumed either or implementation should suffice. Even in my > implementation the error checks assumes either of the two should be > available else to fail the pwmchip_add Your implementation requires that users call either pwm_config() or pwm_config_alternate(). PWM drivers may only have to implement either callback, but users will be required to support both (or otherwise only work with a subset of PWM drivers). Thierry
Attachment:
pgpkFrcxw5K0U.pgp
Description: PGP signature
_______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
