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Subject[RFC PATCH] 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.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
---
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(+)

diff --git a/drivers/video/atmel_lcdfb.c b/drivers/video/atmel_lcdfb.c
index b004036..f2e8d1b 100644
--- a/drivers/video/atmel_lcdfb.c
+++ b/drivers/video/atmel_lcdfb.c
@@ -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);




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