On Friday 24 February 2012, Thierry Reding wrote: > * Arnd Bergmann wrote: > > On Thursday 23 February 2012, Thierry Reding wrote: > > > * Arnd Bergmann wrote: > [...] > > > > * Why not include the pwm_request() call in this and return the > > > > pwm_device directly? You said that you want to get rid of the > > > > pwm_id eventually, which is a good idea, but this interface still > > > > forces one to use it. > > > > > > Okay, that sounds sensible. I propose to rename the function to something like > > > of_request_pwm(). > > > > Sounds good. On second thought, I would actually prefer starting the name with pwm_ and making it independent of device tree. There might be other ways how to find the pwm_device from a struct device in the future, but it should always be possible using a device together with a string and/or numeric identifier, much in the same way that we can get a resource from a platform_device. Ideally, there would be a common theme behind finding a memory region, irq, gpio pin, clock, regulator, dma-channel and pwm or anything else that requires a link between two device nodes. > > > It would of course need an additional parameter (name) to > > > forward to pwm_request(). > > > > Not necessarily, it could use the dev_name(device) or the name > > of the property, or a combination of the two. > > The problem with that is that usually the device would be named something > generic like "pwm", while in case where the PWM is used for the backlight > it makes sense to label the PWM device "backlight". > > Looking at debugfs and seeing an entry "backlight" is much more straight- > forward than "pwm.0". I mean "pwm.0" doesn't carry any useful information > really, does it? But the device name would be from the device using the pwm, not the pwm controller, so it should be something more helpful, no? > > > > > +EXPORT_SYMBOL(of_get_named_pwm); > > > > > > > > EXPORT_SYMBOL_GPL? > > > > > > It was brought up at some point that it might be nice to allow non-GPL > > > drivers to use the PWM framework as well. I don't remember any discussion > > > resulting from the comment. Perhaps we should have that discussion now and > > > decide whether or not we want to keep it GPL-only or not. > > > > I would definitely use EXPORT_SYMBOL_GPL for all new code unless it > > replaces an earlier interface that was available as EXPORT_SYMBOL. > > I just grepped the code and noticed this: > > $ $ git grep -n 'EXPORT_SYMBOL.*(pwm_request)' > arch/arm/mach-vt8500/pwm.c:139:EXPORT_SYMBOL(pwm_request); > arch/arm/plat-mxc/pwm.c:183:EXPORT_SYMBOL(pwm_request); > arch/arm/plat-samsung/pwm.c:83:EXPORT_SYMBOL(pwm_request); > arch/unicore32/kernel/pwm.c:132:EXPORT_SYMBOL(pwm_request); > drivers/mfd/twl6030-pwm.c:156:EXPORT_SYMBOL(pwm_request); > drivers/misc/ab8500-pwm.c:108:EXPORT_SYMBOL(pwm_request); > drivers/pwm/core.c:262:EXPORT_SYMBOL_GPL(pwm_request); > > It seems like the legacy PWM API used to be non-GPL. Should I switch it back? > Also does it make sense to have something like of_request_pwm() GPL when the > rest of the API isn't? I guess the choice is to make between you and Sascha. The implementation is new, so you could pick EXPORT_SYMBOL_GPL, but you could also try to keep to the current API. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
