From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thierry Reding Date: Wed, 23 Oct 2013 10:58:22 +0000 Subject: Re: How to set fops in "struct platform_pwm_backlight_data"? Message-Id: <20131023105821.GC15082@ulmo.nvidia.com> MIME-Version: 1 Content-Type: multipart/mixed; boundary="gr/z0/N6AeWAPJVB" List-Id: References: <5260BD8C.7000200@gmail.com> <20131022072443.GB8681@ulmo.nvidia.com> <52663D6D.5000806@gmail.com> <20131022124905.GA24255@ulmo.nvidia.com> <52673178.8070805@gmail.com> <20131023080002.GB7404@ulmo.nvidia.com> <52678D99.8090003@gmail.com> <20131023090925.GC11954@ulmo.nvidia.com> <5267A691.8050503@gmail.com> <5267A8F9.9050907@gmail.com> In-Reply-To: <5267A8F9.9050907@gmail.com> To: Mark Zhang Cc: rpurdie@rpsys.net, jg1.han@samsung.com, Jean-Christophe PLAGNIOL-VILLARD , tomi.valkeinen@ti.com, linux-pwm@vger.kernel.org, "linux-fbdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" --gr/z0/N6AeWAPJVB Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Oct 23, 2013 at 06:46:17PM +0800, Mark Zhang wrote: > On 10/23/2013 06:36 PM, Mark Zhang wrote: > > On 10/23/2013 05:09 PM, Thierry Reding wrote: > >> On Wed, Oct 23, 2013 at 04:49:29PM +0800, Mark Zhang wrote: > >>> On 10/23/2013 04:00 PM, Thierry Reding wrote: > >>>> On Wed, Oct 23, 2013 at 10:16:24AM +0800, Mark Zhang wrote: > >>>>> On 10/22/2013 08:49 PM, Thierry Reding wrote: > >>>>>> On Tue, Oct 22, 2013 at 04:55:09PM +0800, Mark Zhang wrote: > >>>>>>> On 10/22/2013 03:24 PM, Thierry Reding wrote: > >>>>>>>> On Fri, Oct 18, 2013 at 12:48:12PM +0800, Mark Zhang wrote: > >>>>>>> [...] > >>>>>>>>>> > >>>>>>>>> > >>>>>>>>> Okay, I just want to set the "notify" function pointer in "stru= ct > >>>>>>>>> platform_pwm_backlight_data", because I want to tune the bright= ness > >>>>>>>>> value before the pwm-bl sets the brightness to hardware. I don'= t know > >>>>>>>>> how to do that, unless we define the platform data explicitly. > >>>>>>>> > >>>>>>>> Okay, my question should have been what you need the functions f= or and > >>>>>>>> why you think you need them. > >>>>>>>> > >>>>>>> > >>>>>>> If I understanding you correctly, I suppose I've said that: "beca= use I > >>>>>>> want to tune the brightness value before the pwm-bl sets the brig= htness > >>>>>>> to hardware". > >>>>>> > >>>>>> Why do you want to tune the brightness value? What are you trying = to > >>>>>> achieve? > >>>>>> > >>>>> > >>>>> Oh, Tegra has a feature named PRISM(aka SmartDimmer). It changes the > >>>>> color value to make the display looks bright so that we can reduce = the > >>>>> backlight brightness to save power. So everytime PRISM is triggered= , we > >>>>> call "backlight_update_status", then in the "notify" callback, we c= hange > >>>>> the brightness value which pwm-bl provides by considering the PRISM > >>>>> compensations. > >>>> > >>>> If you automatically call backlight_update_status() everytime PRISM > >>>> gives you new data, can't you just pass the correct value in in the > >>>> first place so that you don't have to tweak it in the .notify() > >>>> callback? > >>> > >>> OK, how to do that? -- "pass the correct value in in the first place"? > >> > >> Well, if you call backlight_update_status(), then you can pass in a > >> brightness value, right? You usually do that by setting the backlight's > >> props.brightness field. > >> > >> So when PRISM gives you new data, you could just read out the current > >> brightness, compute the new one based on the current one and the PRISM > >> data, set the props.brightness field to that value and then call > >> backlight_update_status(). > >> > >=20 > > Okay, anyway, I got the idea. Actually it's simpler. :) > > I'm just curious that if we can do that in this way, why we need > > "notify" anymore? >=20 > Oh, by the way, how about "check_fb" fops? Is there some kind of > substitution as well? I mean, if I wanna set "check_fb" and also want to > define the backlight device via DT, is there a way to do that? No, there's no substitution for that. .check_fb() is used to verify that a backlight device is associated with a framebuffer device. There are better ways to check for that with DT, although nothing has been merged into mainline yet. Thierry --gr/z0/N6AeWAPJVB Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) iQIcBAEBAgAGBQJSZ6vNAAoJEN0jrNd/PrOheogQAKfa4VWTqzXxAE2s8g5+gh8U Bb3L0ijlG0dedBXW5awc7uhvJzdebw4SrV5tgEyt4+bXPajBQx3GPZmGj1viMx9h mc5Mgx9czPH/vwdKBqRRVqF5URP8xgJ7QrXClf2cim2g5dl/A4G+hBJuOLpiU4jG YGDaFIdSNWnbAMtPno/VPPGdgHYm4qIC0qWrXlMA+7xmY7GpH5TK4f36HLxcIGVL Oud1b4vGZ6PLoVLXt46l8oJKMoUNdi9E+FuVzYLkNWa2H9fm6Q286P0NG20uDC8Z wQjIxzC1yg0biCXlLUYPhWtDJQ9+e78KEHwb0mi+CmxxgT0WbMVYELDGrOXYSOat vK64qMvZk7JqsWbDMLUZVkPxx/q9hSct9vq2vbJWHMgiBcINvd4WLMsnevX1yzHl /HRGyBVv+sgJjE/GbyzXQCm7eY4NJnGGqluWefvNvbhPFFTmUJB1p6Uk7bNCnKGn +BGAAt8hUezFM6iFXL36/SbRyUE0UMgX8qkZZO3/YyVLMw3tCeYb/aKJ4Zomgxa9 728hT8y7TCUUIDsKVF4T/csGROa9YfsJSHcc4XzekEYHitXHJzhwyvH9weRusGDe leZduW0c4Gr08HaiJxF/phU1tcqqEDjhfWlzYrAUC1n3dc4WUjs7azd72EghBwEJ 6ydP9PiwdoTto3Uad9Ih =8ADE -----END PGP SIGNATURE----- --gr/z0/N6AeWAPJVB--