Re: [Linux-fbdev-devel] [PATCH 3/4] [ARM] s3c-fb: Add support for display panning

[Krzysztof H. <krz...@po...>]

On Thu, 09 Jul 2009 17:09:00 +0200
Pawel Osciak <p.o...@sa...> wrote:

> Added support for panning the display in all directions.
> 
> 
> Reviewed-by: Marek Szyprowski <m.s...@sa...>
> Reviewed-by: Kyungmin Park <kyu...@sa...>
> Signed-off-by: Pawel Osciak <p.o...@sa...>
> 
> 
> 
> diff --git a/drivers/video/s3c-fb.c b/drivers/video/s3c-fb.c
> index ff0b1a3..77b77a2 100644
> --- a/drivers/video/s3c-fb.c
> +++ b/drivers/video/s3c-fb.c
> @@ -294,6 +294,8 @@ static int s3c_fb_set_par(struct fb_info *info)
>  	}
>  
>  	info->fix.line_length = (var->xres_virtual * var->bits_per_pixel) / 8;
> +	info->fix.xpanstep = info->var.xres_virtual > info->var.xres ? 1 : 0;
> +	info->fix.ypanstep = info->var.yres_virtual > info->var.yres ? 1 : 0;
>  

These two lines are not need. If the xres_virtual > xres  there is no 
panning possible (the same is true for yres and yres_virtual).

>  	/* disable the window whilst we update it */
>  	writel(0, regs + WINCON(win_no));
> @@ -640,6 +642,38 @@ static int s3c_fb_blank(int blank_mode, struct fb_info *info)
>  	return 0;
>  }
>  
> +/**
> + * s3c_fb_pan_display() - Pan the display.
> + *
> + * Note, that the offsets can be written to the device at any time, as their
> + * values are latched at each vsync automatically. This also means that only
> + * the last call to this function will have any effect on next vsync, but
> + * there is no need to sleep waiting for it to prevent tearing.
> + *
> + * @var: The screen information to verify.
> + * @info: The framebuffer device.
> + */
> +static int s3c_fb_pan_display(struct fb_var_screeninfo *var,
> +			      struct fb_info *info)
> +{
> +	struct s3c_fb_win *win	= info->par;
> +	struct s3c_fb *sfb	= win->parent;
> +	unsigned int start_byte_offset, end_byte_offset;
> +
> +	/* Offset in bytes to the start of the displayed area */
> +	start_byte_offset = var->yoffset * info->fix.line_length
> +			    + var->xoffset * (info->var.bits_per_pixel) / 8;
> +	writel(info->fix.smem_start + start_byte_offset,
> +	       sfb->regs + VIDW_BUF_START(win->index));
> +

Check out carefully what units are used for VIDW_BUF_START (pixels, bytes, words, 
dwords). This x panning may not work on all depths supported by the driver
(18-bit, 19-bit, 1-bit, etc). Do you really want panning in the x direction?
Please test it in all depths.

Regards,
Krzysztof
 


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