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    SubjectRe: [v1,1/3] drm/panel: ili9341: Correct use of device property APIs
    On Fri, Apr 26, 2024 at 02:08:16AM +0800, Sui Jingfeng wrote:
    > On 2024/4/25 22:26, Andy Shevchenko wrote:
    > > It seems driver missed the point of proper use of device property APIs.
    > > Correct this by updating headers and calls respectively.
    >
    > You are using the 'seems' here exactly saying that you are not 100% sure.
    >
    > Please allow me to tell you the truth: This patch again has ZERO effect.
    > It fix nothing. And this patch is has the risks to be wrong.

    Huh?! Really, stop commenting the stuff you do not understand.

    > Simple because the "ili9341_probe() ---> ili9341_dbi_prob()" code path
    > is DT dependent.
    >
    > First of all, the devm_of_find_backlight() is called in ili9341_dbi_probe()
    > under *non-DT* environment, devm_of_find_backlight() is just a just a
    > no-op and will return NULL. NULL is not an error code, so ili9341_dbi_probe()
    > won't rage quit. But the several side effect is that the backlight will
    > NOT works at all.

    Is it a problem?

    > It is actually considered as fatal bug for *panels* if the backlight of
    > it is not light up, at least the brightness of *won't* be able to adjust.
    > What's worse, if there is no sane platform setup code at the firmware
    > or boot loader stage to set a proper initial state. The screen is complete
    > dark. Even though the itself panel is refreshing framebuffers, it can not
    > be seen by human's eye. Simple because of no backlight.

    Can you imagine that I may have different hardware that considered
    this is non-fatal error?

    > Second, the ili9341_dbi_probe() requires additional device properties to
    > be able to works very well on the rotation screen case. See the calling
    > of "device_property_read_u32(dev, "rotation", &rotation)" in
    > ili9341_dbi_probe() function.

    Yes, exactly, and how does it object the purpose of this patch?

    > Combine with those two factors, it is actually can conclude that the
    > panel-ilitek-ili9394 driver has the *implicit* dependency on 'OF'.
    > Removing the 'OF' dependency from its Kconfig just trigger the
    > leakage of such risks.

    What?!

    > My software node related patches can help to reduce part of the potential
    > risks, but it still need some extra work. And it is not landed yet.

    Your patch has nothing to do with this series.

    --
    With Best Regards,
    Andy Shevchenko



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