[PATCH] backlight: platform_lcd: introduce probe callback

[PATCH] backlight: platform_lcd: introduce probe callback

[Andrew Bresticker]

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.

Signed-off-by: Andrew Bresticker <abrestic@chromium.org>
---
 drivers/video/backlight/platform_lcd.c | 8 ++++++++
 include/video/platform_lcd.h           | 1 +
 2 files changed, 9 insertions(+)

diff --git a/drivers/video/backlight/platform_lcd.c b/drivers/video/backlight/platform_lcd.c
index 54d94de..2fb24a1 100644
--- a/drivers/video/backlight/platform_lcd.c
+++ b/drivers/video/backlight/platform_lcd.c
@@ -86,6 +86,14 @@ static int platform_lcd_probe(struct platform_device *pdev)
 		return -EINVAL;
 	}
 
+	if (pdata->probe) {
+		err = pdata->probe(pdata);
+		if (err) {
+			dev_err(dev, "platform probe failed: %d\n", 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 *);
 };
-- 
1.8.1.3

Re: [PATCH] backlight: platform_lcd: introduce probe callback

[Doug Anderson]

Andrew,

On Thu, Apr 11, 2013 at 11:36 AM, Andrew Bresticker
<abrestic@chromium.org> wrote:
> +       if (pdata->probe) {
> +               err = pdata->probe(pdata);
> +               if (err) {
> +                       dev_err(dev, "platform probe failed: %d\n", err);

It would probably be good not to print in the case of -EPROBE_DEFER?

Otherwise this looks good to me.

-Doug

Re: [PATCH] backlight: platform_lcd: introduce probe callback

[Andrew Bresticker]

> It would probably be good not to print in the case of -EPROBE_DEFER?

Actually, I think I'll just kill the print all together since the
caller will print something anyways.

-Andrew

[PATCH v2] backlight: platform_lcd: introduce probe callback

[Andrew Bresticker]

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.

Signed-off-by: Andrew Bresticker <abrestic@chromium.org>
---
 drivers/video/backlight/platform_lcd.c | 6 ++++++
 include/video/platform_lcd.h           | 1 +
 2 files changed, 7 insertions(+)

diff --git a/drivers/video/backlight/platform_lcd.c b/drivers/video/backlight/platform_lcd.c
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 *);
 };
-- 
1.8.1.3

Re: [PATCH v2] backlight: platform_lcd: introduce probe callback

[Doug Anderson]

Andrew,

On Thu, Apr 11, 2013 at 1:24 PM, Andrew Bresticker
<abrestic@chromium.org> wrote:
> 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.
>
> Signed-off-by: Andrew Bresticker <abrestic@chromium.org>
> ---
>  drivers/video/backlight/platform_lcd.c | 6 ++++++
>  include/video/platform_lcd.h           | 1 +
>  2 files changed, 7 insertions(+)

Reviewed-by: Doug Anderson <dianders@chromium.org>

Re: [PATCH v2] backlight: platform_lcd: introduce probe callback

[Jingoo Han]

On Friday, April 12, 2013 5:25 AM, Andrew Bresticker wrote:
> 
> 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.
> 
> Signed-off-by: Andrew Bresticker <abrestic@chromium.org>

CC'ed Andrew Morton,

It looks good.
Acked-by: Jingoo Han <jg1.han@samsung.com>

Best regards,
Jingoo Han


> ---
>  drivers/video/backlight/platform_lcd.c | 6 ++++++
>  include/video/platform_lcd.h           | 1 +
>  2 files changed, 7 insertions(+)
> 
> diff --git a/drivers/video/backlight/platform_lcd.c b/drivers/video/backlight/platform_lcd.c
> 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 *);
>  };
> --
> 1.8.1.3
> 

Re: [PATCH v2] backlight: platform_lcd: introduce probe callback

[Andrew Morton]

On Thu, 11 Apr 2013 13:24:50 -0700 Andrew Bresticker <abrestic@chromium.org> wrote:

> 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?

Re: [PATCH v2] backlight: platform_lcd: introduce probe callback

[Jingoo Han]

On Tuesday, April 16, 2013 8:07 AM, Andrew Morton wrote:
> 
> On Thu, 11 Apr 2013 13:24:50 -0700 Andrew Bresticker <abrestic@chromium.org> wrote:
> 
> > 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