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    SubjectRe: [PATCH 5/8] fbdev: ssd1307fb: Add module parameter bitsperpixel.
    Am Tue, 10 Mar 2015 12:45:49 +0200
    schrieb Tomi Valkeinen <tomi.valkeinen@ti.com>:

    > On 14/02/15 17:54, Maxime Ripard wrote:
    > > On Sat, Feb 07, 2015 at 05:05:03PM +0100, Thomas Niederprüm wrote:
    > >> Am Sat, 7 Feb 2015 12:20:43 +0100
    > >> schrieb Maxime Ripard <maxime.ripard@free-electrons.com>:
    > >>
    > >>> On Fri, Feb 06, 2015 at 11:28:11PM +0100, niederp@physik.uni-kl.de
    > >>> wrote:
    > >>>> From: Thomas Niederprüm <niederp@physik.uni-kl.de>
    > >>>>
    > >>>> This patch adds a module parameter 'bitsperpixel' to adjust the
    > >>>> colordepth of the framebuffer. All values >1 will result in
    > >>>> memory map of the requested color depth. However only the MSB of
    > >>>> each pixel will be sent to the device. The framebuffer
    > >>>> identifies itself as a grayscale display with the specified
    > >>>> depth.
    > >>>
    > >>> I'm not sure this is the right thing to do.
    > >>>
    > >>> The bits per pixel for this display is rightfully defined, used
    > >>> and reported to the userspace, why would you want to change that?
    > >>
    > >> You are right of course. The display is 1bpp and it reports to be 1
    > >> bpp. The problem is that there is almost no userspace library that
    > >> can handle 1 bit framebuffers correctly. So it is nice if the
    > >> framebuffer (optionally) can expose itself as 8 bits per pixel
    > >> grayscale to the userspace program. As an example this allows to
    > >> run DirectFB on the framebuffer, which is not possible out of the
    > >> box for 1bpp.
    > >>
    > >> Also note that if do not set the module parameter at load time
    > >> the framebuffer will be 1bpp. So you have to actively set that
    > >> module parameter to make the framebuffer pretend to be more than
    > >> 1bpp.
    > >>
    > >> In any case I don't cling to that patch, I just thought it was a
    > >> nice feature.
    > >
    > > I'd say that the right fix would be to patch DirectFB, instead of
    > > faking that in the kernel.
    > >
    > > But again, that's probably Tomi's call, not mine.
    >
    > Right, I'm not thrilled =). I don't think it's a good idea to lie to
    > the userspace (except when fixing regressions).

    Ok, since Maxime and you agree that this is not desirable I will drop
    that patch in v4.

    Thomas


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