atmel_lcdfb: avoid division by zero

Avoid division by zero in atmel_lcdfb_check_var() function.

If pixclock is not specified while passing a var structure in the check_var() funtion, a division by zero occurs (when translating pixclock to KHz).

This patch adds a checking of this value and try to choose a video mode in the modelist.

The mode found in the probe function in added to the modelist.

---
Please tell me if it is a proper way to implement a mean of having a good var in check_var() function.
Is an -EINVAL error is legitimate in the case of a zero value for pixclock or bits_per_pixel (if I cannot find a good modeline) ?

drivers/video/atmel_lcdfb.c | 36 ++++++++++++++++++++++++++++++++++

1 file changed, 36 insertions(+)

index b004036..f2e8d1b 100644
@@ -256,6 +256,21 @@ static int atmel_lcdfb_alloc_video_memory(struct atmel_lcdfb_info *sinfo)

	return 0;
}

+static const struct fb_videomode *atmel_lcdfb_choose_mode(struct fb_var_screeninfo *var,
+ struct fb_info *info)
+{
+ struct fb_videomode varfbmode;
+ const struct fb_videomode *fbmode = NULL;
+
+ fb_var_to_videomode(&varfbmode, var);
+ fbmode = fb_find_nearest_mode(&varfbmode, &info->modelist);
+ if (fbmode) {
+ fb_videomode_to_var(var, fbmode);
+ }
+ return fbmode;
+}
+
+
/**
* atmel_lcdfb_check_var - Validates a var passed in.
* @var: frame buffer variable screen structure
@@ -289,6 +304,15 @@ static int atmel_lcdfb_check_var(struct fb_var_screeninfo *var,

	clk_value_khz = clk_get_rate(sinfo->lcdc_clk) / 1000;

	dev_dbg(dev, "%s:\n", __func__);

+
+ if (!(var->pixclock && var->bits_per_pixel)) {
+ /* choose a suitable mode if possible */
+ if (!atmel_lcdfb_choose_mode(var, info)) {
+ dev_err(dev, "needed value not specified\n");
+ return -EINVAL;
+ }
+ }
+

	dev_dbg(dev, "  resolution: %ux%u\n", var->xres, var->yres);
	dev_dbg(dev, "  pixclk:     %lu KHz\n", PICOS2KHZ(var->pixclock));
	dev_dbg(dev, "  bpp:        %u\n", var->bits_per_pixel);
@@ -299,6 +323,13 @@ static int atmel_lcdfb_check_var(struct fb_var_screeninfo *var,
		return -EINVAL;
	}

+ /* Do not allow to have real resoulution larger than virtual */
+ if (var->xres > var->xres_virtual)
+ var->xres_virtual = var->xres;
+
+ if (var->yres > var->yres_virtual)
+ var->yres_virtual = var->yres;
+

	/* Force same alignment for each line */
	var->xres = (var->xres + 3) & ~3UL;
	var->xres_virtual = (var->xres_virtual + 3) & ~3UL;
@@ -691,6 +722,7 @@ static int __init atmel_lcdfb_probe(struct platform_device *pdev)
	struct fb_info *info;
	struct atmel_lcdfb_info *sinfo;
	struct atmel_lcdfb_info *pdata_sinfo;
+	struct fb_videomode fbmode;
	struct resource *regs = NULL;
	struct resource *map = NULL;
	int ret;
@@ -853,6 +885,10 @@ static int __init atmel_lcdfb_probe(struct platform_device *pdev)
		goto free_cmap;
	}

+ /* add selected videomode to modelist */
+ fb_var_to_videomode(&fbmode, &info->var);
+ fb_add_videomode(&fbmode, &info->modelist);
+

	/* Power up the LCDC screen */
	if (sinfo->atmel_lcdfb_power_control)
		sinfo->atmel_lcdfb_power_control(1);