From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vladimir Zapolskiy Date: Fri, 07 Nov 2014 14:57:57 +0000 Subject: Re: [PATCH 1/2] backlight: pwm: don't call legacy pwm request for device defined in dt Message-Id: <545CDDF5.70905@mentor.com> List-Id: References: <1413035186-11771-1-git-send-email-vladimir_zapolskiy@mentor.com> <1413035186-11771-2-git-send-email-vladimir_zapolskiy@mentor.com> <20141107134848.GB31950@ulmo> <545CD4DC.4030409@mentor.com> In-Reply-To: <545CD4DC.4030409@mentor.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Thierry Reding Cc: linux-fbdev@vger.kernel.org, linux-pwm@vger.kernel.org, Jingoo Han , Bryan Wu , Lee Jones Thierry, On 07.11.2014 16:19, Vladimir Zapolskiy wrote: > Hi Thierry, > > On 07.11.2014 15:48, Thierry Reding wrote: >> On Sat, Oct 11, 2014 at 04:46:25PM +0300, Vladimir Zapolskiy wrote: >>> Platform PWM backlight data provided by board's device tree should be >>> complete enough to successfully request a pwm device using pwm_get() API. >>> >>> Based on initial implementation done by Dmitry Eremin-Solenikov. >>> >>> Reported-by: Dmitry Eremin-Solenikov >>> Signed-off-by: Vladimir Zapolskiy >>> Cc: Thierry Reding >>> Cc: Jingoo Han >>> Cc: Bryan Wu >>> Cc: Lee Jones >>> --- >>> drivers/video/backlight/pwm_bl.c | 14 +++++++------- >>> 1 file changed, 7 insertions(+), 7 deletions(-) >> >> I don't really understand what this is supposed to do. The commit >> message doesn't make a very good job of explaining it either. >> >> Can you describe in more detail what problem this fixes and why it >> should be merged? > > thank you for review. > > As it is shown by the code this particular change rejects fallback to > legacy PWM device request (which itself in turn is fixed in the next > commit) for boards with supplied DTS, "pwm-backlight" compatible node > and unregistered corresponding PWM device in that node. > > I don't know if there is a good enough reason to register PWM backlight > device connected to some quite arbitrary PWM device, if no PWM device > information is given in the "pwm-backlight" compatible node, so I think > it makes sense to change the default policy. > also please note that Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt quite fairly describes "pwms" as a required property, but right now this statement from the documentation is wrong, it is possible to register pwm-backlight device driver (using notorious pwm_request() legacy API) connected to some unspecified pwm device. I don't think that the current registration policy is correct, that's why I propose to fix the logic instead of making a documentation update. -- With best wishes, Vladimir