[Freedreno] [DPU PATCH v2 2/2] drm/panel: add backlight control support for truly panel

[abhinavk at codeaurora.org]

Hi Bjorn

Apologies if the prev reply wasnt clear.

Hope this one is.

reply inline.

On 2018-04-17 14:29, Bjorn Andersson wrote:
> On Tue 17 Apr 11:21 PDT 2018, abhinavk at codeaurora.org wrote:
>> On 2018-04-16 23:13, Bjorn Andersson wrote:
> [..]
>> > If the panel isn't actually a piece of backlight hardware then it should
>> > not register a backlight device. Why do you need your own sysfs?
>> >
>> > Regards,
>> > Bjorn
>> [Abhinav] This particular panel isnt a piece of backlight hardware.
>> But, we want to have our own sysfs to give flexibility to our 
>> userspace
>> to write and read stuff for its proprietary uses.
> 
> Please be more specific in your replies, no one will accept code that
> "does stuff" and expecting a reviewer to spend time guessing or pulling
> the information out of you is a sure way to get your patches ignored.
> 
> Exactly what kind of stuff are you talking about here and exactly which
> problem are you solving.
> 
>> Thats how our downstream has been working so far and hence to maintain
>> the compatibility would like to have it.
> 
> Make your proprietary code work with the upstream kernel and you
> shouldn't ever have to modify it.
> 
> Regards,
> Bjorn

[Abhinav] We have a few userspace clients today for the backlight sysfs 
node
which read/write directly to 
"/sys/class/backlight/panel0-backlight/brightness"
When I said "stuff" I was only referring to the brightness value.
This separate sysfs node allows us to validate those userspace features 
of ours
which directly edit the backlight value on our reference platform.
Since our reference platform uses this panel,hence having our own sysfs 
alias helps.
Otherwise, whenever we try to use this panel with upstream code we will 
have to end up
changing all those places in our userspace/framework to change the sysfs 
path.
Hence we wanted to preserve that sysfs node name.
The wled device is not created under /sys/class/backlight but under
/sys/class/leds/wled.
So we will have to change the name of this node across all our 
userspace.

If this isnt a convincing reason enough to have its own sysfs node path, 
I will use
your approach.

Let me know your comments or if this is still not clear.

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