On Tuesday, April 16, 2013 8:07 AM, Andrew Morton wrote:

On Thu, 11 Apr 2013 13:24:50 -0700 Andrew Bresticker [off-list ref] wrote:

quoted

Platform LCD devices may need to do some device-specific
initialization before they can be used (regulator or GPIO setup,
for example), but currently the driver does not support any way of
doing this.  This patch adds a probe() callback to plat_lcd_data
which platform LCD devices can set to indicate that device-specific
initialization is needed.

index 17a6b83..f46180e 100644

--- a/drivers/video/backlight/platform_lcd.c
+++ b/drivers/video/backlight/platform_lcd.c

@@ -86,6 +86,12 @@ static int platform_lcd_probe(struct platform_device *pdev)
 		return -EINVAL;
 	}

+	if (pdata->probe) {
+		err = pdata->probe(pdata);
+		if (err)
+			return err;
+	}
+
 	plcd = devm_kzalloc(&pdev->dev, sizeof(struct platform_lcd),
 			    GFP_KERNEL);
 	if (!plcd) {

diff --git a/include/video/platform_lcd.h b/include/video/platform_lcd.h
index ad3bdfe..23864b2 100644
--- a/include/video/platform_lcd.h
+++ b/include/video/platform_lcd.h

@@ -15,6 +15,7 @@ struct plat_lcd_data;
 struct fb_info;

 struct plat_lcd_data {
+	int	(*probe)(struct plat_lcd_data *);
 	void	(*set_power)(struct plat_lcd_data *, unsigned int power);
 	int	(*match_fb)(struct plat_lcd_data *, struct fb_info *);
 };

Sigh.  I see that this entire interface has been lovingly undocumented.
It's an invitation for us to grow bugs, incompatibilities, leaks, etc.

Possible example: what happens if pdata->probe does some resource
allocation or device initialisation which should be backed out if, say,
platform_lcd_probe() later fails?

Hi Andrew,

I agree with you.
Indeed, the documentation is necessary.

Andrew Bresticker,
Would you make the document?
It would be very helpful.

Best regards,
Jingoo Han