On Mon, Feb 24, 2025 at 01:38:32PM +0000, Aditya Garg wrote:
> From: Kerem Karabay <kekrby@xxxxxxxxx>
>
> Add XRGB8888 emulation helper for devices that only support BGR888.
...
> +static void drm_fb_xrgb8888_to_bgr888_line(void *dbuf, const void *sbuf, unsigned int pixels)
Okay the xrgb8888 is the actual pixel format independently on
the CPU endianess.
> +{
> + u8 *dbuf8 = dbuf;
> + const __le32 *sbuf32 = sbuf;
But here we assume that sbuf is __le32.
And I think we may benefit from the __be32 there.
> + unsigned int x;
> + u32 pix;
> +
> + for (x = 0; x < pixels; x++) {
> + pix = le32_to_cpu(sbuf32[x]);
> + /* write red-green-blue to output in little endianness */
> + *dbuf8++ = (pix & 0x00ff0000) >> 16;
> + *dbuf8++ = (pix & 0x0000ff00) >> 8;
> + *dbuf8++ = (pix & 0x000000ff) >> 0;
pix = be32_to_cpu(sbuf[4 * x]) >> 8;
put_unaligned_le24(pix, &dbuf[3 * x]);
> + }
Or, after all, this __le32 magic might be not needed at all. Wouldn't the below
be the equivalent
static void drm_fb_xrgb8888_to_bgr888_line(void *dbuf, const void *sbuf, unsigned int pixels)
{
unsigned int x;
u32 pix;
for (x = 0; x < pixels; x++) {
/* Read red-green-blue from input in big endianess and... */
pix = get_unaligned_be24(sbuf + x * 4 + 1);
/* ...write it to output in little endianness. */
put_unaligned_le24(pix, dbuf + x * 3);
}
}
The comments can even be dropped as the code quite clear about what's going on.
> +}
But it's up to you. I don't know which solution gives better code generation
either.
--
With Best Regards,
Andy Shevchenko
