Re: [PATCH 1/2] OMAPDSS: panel-dvi: Add Kconfig dependency on I2C

[Tomi Valkeinen <tomi.valkeinen@ti.com>]

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On Wed, 2012-02-29 at 10:03 +0000, Florian Tobias Schandinat wrote:
> On 02/29/2012 08:48 AM, Tomi Valkeinen wrote:
> > panel-dvi uses i2c, but the Kconfig didn't have dependency on I2C. Add
> > it.
> > 
> > Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
> > ---
> >  drivers/video/omap2/displays/Kconfig |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> > 
> > diff --git a/drivers/video/omap2/displays/Kconfig b/drivers/video/omap2/displays/Kconfig
> > index 74d29b5..408a992 100644
> > --- a/drivers/video/omap2/displays/Kconfig
> > +++ b/drivers/video/omap2/displays/Kconfig
> > @@ -12,7 +12,7 @@ config PANEL_GENERIC_DPI
> >  
> >  config PANEL_DVI
> >  	tristate "DVI output"
> > -	depends on OMAP2_DSS_DPI
> > +	depends on OMAP2_DSS_DPI && I2C
> 
> It's just a matter of taste, but are you sure you want to "depend" on it and not
> "select" it? Other drivers tend to use select for I2C, for me it doesn't really
> matter.

Well, I'd like to "select", but I don't think that's correct. From
Documentation/kbuild/kconfig-language.txt:

        In general use select only for non-visible symbols
        (no prompts anywhere) and for symbols with no dependencies.

But I do see quite many selects for I2C, so I'm not sure if all those
are wrong, or has it just been decided that I2C is a valid target for
select.

Using depend is in line with the other panel drivers in the same
directory. I've been thinking about the same thing from time to time,
and I'd rather select I2C, SPI and BACKLIGHT_CLASS_DEVICE than use
depend.

But, for example, using select to BACKLIGHT_CLASS_DEVICE is broken: if I
change a panel driver to select BACKLIGHT_CLASS_DEVICE, but then I
manually disable CONFIG_BACKLIGHT_LCD_SUPPORT (which the
BACKLIGHT_CLASS_DEVICE depends on) from the kernel config, this leads to
BACKLIGHT_CLASS_DEVICE being enabled, but CONFIG_BACKLIGHT_LCD_SUPPORT
being disabled, which is clearly broken.

So... As I see it, depending is a bit awkward, but it's correct.

 Tomi


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