Re: [PATCH v4 1/6] drm/format-helper: Add drm_fb_xrgb8888_to_gray8_line()

[Thomas Zimmermann]

Hi

Am 11.02.22 um 12:12 schrieb Andy Shevchenko:
> On Fri, Feb 11, 2022 at 11:40:13AM +0100, Javier Martinez Canillas wrote:
> > On 2/11/22 11:28, Andy Shevchenko wrote:
> > > On Fri, Feb 11, 2022 at 10:19:22AM +0100, Javier Martinez Canillas wrote:
>
> ...
>
> > > > +static void drm_fb_xrgb8888_to_gray8_line(u8 *dst, const u32 *src, unsigned int pixels)
> > > > +{
> > > > +	unsigned int x;
> > > > +
> > > > +	for (x = 0; x < pixels; x++) {
> > > > +		u8 r = (*src & 0x00ff0000) >> 16;
> > > > +		u8 g = (*src & 0x0000ff00) >> 8;
> > > > +		u8 b =  *src & 0x000000ff;
> > > > +
> > > > +		/* ITU BT.601: Y = 0.299 R + 0.587 G + 0.114 B */
> > > > +		*dst++ = (3 * r + 6 * g + b) / 10;
> > > > +		src++;
> > > > +	}
> > >
> > > Can be done as
> > >
> > > 	while (pixels--) {
> > > 		...
> > > 	}
> > >
> > > or
> > >
> > > 	do {
> > > 		...
> > > 	} while (--pixels);
> >
> > I don't see why a while loop would be an improvement here TBH.
>
> Less letters to parse when reading the code.

It's a simple refactoring of code that has worked well so far. Let's 
leave it as-is for now.

Best regards
Thomas

> > In any case, I just pulled the line conversion logic as a separate
> > function with minimal code changes since doing that should be in a
> > separate patch.
>
>
> > Feel free to post a patch if you want to change that while loop.
>
> Perhaps some day :-)

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

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