On Tue, Apr 7, 2020 at 2:19 PM Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx> wrote: > > On Tue, Apr 07, 2020 at 01:51:42PM +0300, Oleksandr Suvorov wrote: > > On Tue, Apr 7, 2020 at 9:17 AM Uwe Kleine-König > > <u.kleine-koenig@xxxxxxxxxxxxxx> wrote: > > > > > > On Sun, Apr 05, 2020 at 10:22:42PM +0300, Oleksandr Suvorov wrote: > > > > Add the description of PWM_NOFLAGS flag property. > > > > > > > > Signed-off-by: Oleksandr Suvorov <oleksandr.suvorov@xxxxxxxxxxx> > > > > > > As I already wrote in reply to the v1 series I'd prefer a name for 0 > > > that explicitly handles normal polarity. > > > > Uwe, AFAIU, there is no flag that forces normal polarity, the normal polarity > > is the default state if there is no flag to invert the polarity is set. > > Yes, that's the status quo. > > > '0' value in the bit flags cell really means there are no flags set > > for the PWM instance. > > For me the relevance of giving 0 a name is mostly for human consumption. > Currently there is only a single flag encoded in the number in question. > But as soon as we add another, say PWM_AUTOSTART we have the following > possible settings: > > PWM_NOFLAGS > PWM_POLARITY_INVERTED > PWM_AUTOSTART > PWM_POLARITY_INVERTED | PWM_AUTOSTART > > Then for the first two a reader doesn't see if autostart is not in use > because the dt author doesn't know this feature (e.g. because autostart > is too new) or if they don't want autostart at all. > > If however we had PWM_POLARITY_NORMAL and PWM_NO_AUTOSTART to complement > PWM_POLARITY_INVERTED and PWM_AUTOSTART So using this approach, in theory, we'll have several flags that all just equals to 0 (0 << 0, 0 << 1, 0 << 2 ...). What if just describe default states for each flag in the DT documentation? > every flag's setting could be explicit and if there is a device tree that only has > > PWM_POLARITY_NORMAL > > it would be obvious that nobody thought enough about autostarting to > explicitly mention it. If you insist on the flag complement model, I have another suggestion. As the normal polarity is the default state, can we use PWM_NO_POLARITY_INVERTED instead of PWM_POLARITY_NORMAL? It gives us 2 benefits: 1. The name will not interfere with enum PWM_POLARITY_NORMAL in <linux/pmw.h> 2. Each flag complement will be made with the same scheme: PWM_flagA -> PWM_NO_flagA... > Best regards > Uwe > > -- > Pengutronix e.K. | Uwe Kleine-König | > Industrial Linux Solutions | https://www.pengutronix.de/ | -- Best regards Oleksandr Suvorov Toradex AG Ebenaustrasse 10 | 6048 Horw | Switzerland | T: +41 41 500 48 00
