linux-kernel - Re: [PATCH v2] fbdev: fix fillrect for 24bpp modes

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Date:	Mon, 20 Apr 2009 16:07:33 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	spock@...too.org
Cc:	krzysztof.h1@...zta.fm, linux-fbdev-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] fbdev: fix fillrect for 24bpp modes

On Sat, 18 Apr 2009 20:52:34 +0200
Michal Januszewski <spock@...too.org> wrote:

>  		while (height--) {
> -			dst += dst_idx >> (ffs(bits) - 1);
> +			dst += dst_idx / bits;
>  			dst_idx &= (bits - 1);
> -			fill_op(p, dst, dst_idx, pat, left, right,
> +			r = dst_idx % bpp;
> +			/* rotate pattern to the correct start position */
> +#ifdef __LITTLE_ENDIAN
> +			pat2 = pat << r | pat >> (bpp-r);
> +#else
> +			pat2 = pat << (bpp-r) | pat >> r;
> +#endif
> +			fill_op(p, dst, dst_idx, pat2, left, right,
>  				width*bpp, bits);
> -			r = (p->fix.line_length*8) % bpp;
> -			pat = pat << (bpp-r) | pat >> r;
>  			dst_idx += p->fix.line_length*8;

hm, that's fairly eye-popping.

Could we do something like

	pat2 = le32_to_cpu(rol32(cpu_to_le32(pat), r));

(might be wrong, but you see what I mean...)
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