On Fri, Feb 11, 2022 at 02:05:56PM +0200, Jani Nikula wrote:
On Fri, 11 Feb 2022, Thomas Zimmermann tzimmermann@suse.de wrote:
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.
IMO *always* prefer a for loop over while or do-while.
The for (i = 0; i < N; i++) is such a strong paradigm in C. You instantly know how many times you're going to loop, at a glance. Not so with with the alternatives, which should be used sparingly.
while () {} _is_ a paradigm, for-loop is syntax sugar on top of it.
And yes, the do-while suggested above is buggy, and you actually need to stop and think to see why.
It depends if pixels can be 0 or not and if it's not, then does it contain last or number.
The do {} while (--pixels); might be buggy iff pixels may be 0.