Re: [PATCH] [media] ov2640: make GPIOLIB an optional dependency

[Mauro Carvalho Chehab <mchehab@s-opensource.com>]

Em Mon, 24 Apr 2017 17:44:02 +0300
Sakari Ailus <sakari.ailus@iki.fi> escreveu:

> Hi Mauro and others,
> 
> On Fri, Apr 21, 2017 at 11:39:42AM -0300, Mauro Carvalho Chehab wrote:
> > Em Fri, 21 Apr 2017 08:33:12 +0200
> > Pavel Machek <pavel@ucw.cz> escreveu:
> >   
> > > Hi!
> > >   
> > > > > Better solution would be for VIDEO_EM28XX_V4L2 to depend on GPIOLIB,
> > > > > too, no? If not, should there be BUG_ON(priv->pwdn_gpio);
> > > > > BUG_ON(priv->resetb_gpio);?    
> > > > 
> > > > Pavel,
> > > > 
> > > > The em28xx driver was added upstream several years the gpio driver. 
> > > > It controls GPIO using a different logic. It makes no sense to make
> > > > it dependent on GPIOLIB, except if someone converts it to use it.    
> > > 
> > > At least comment in the sourcecode...? Remove pwdn_gpio fields from
> > > structure in !GPIOLIB case, because otherwise they are trap for the
> > > programmer trying to understand what is going on?  
> > 
> > 
> > Sorry, I answered to another e-mail thread related to it. I assumed
> > that it was c/c to linux-media, but it is, in fact a private e-mail.  
> 
> I thought so, too! X-)
> 
> > 
> > I can see two alternatives:
> > 
> > 1) Restore old behavior, assuming that all drivers that use OV2640 will
> > have GPIOLIB enabled, with a patch like:
> > 
> > diff --git a/drivers/media/i2c/Kconfig b/drivers/media/i2c/Kconfig
> > index fd181c99ce11..4e834c36f7da 100644
> > --- a/drivers/media/i2c/Kconfig
> > +++ b/drivers/media/i2c/Kconfig
> > @@ -521,6 +521,7 @@ config VIDEO_OV2640
> >         tristate "OmniVision OV2640 sensor support"
> >         depends on VIDEO_V4L2 && I2C
> >         depends on MEDIA_CAMERA_SUPPORT
> > +       depends on GPIOLIB if OF
> >         help
> >           This is a Video4Linux2 sensor-level driver for the OmniVision
> >           OV2640 camera.
> > 
> > However, I was told that some OF drivers don't actually define the GPIO
> > pins.
> > 
> > So, the other option is:
> > 
> > 2) Make the logic smarter for OF, with this change:
> > 
> > 
> > diff --git a/drivers/media/i2c/ov2640.c b/drivers/media/i2c/ov2640.c
> > index 4a2ae24f8722..8855c81a9e1f 100644
> > --- a/drivers/media/i2c/ov2640.c
> > +++ b/drivers/media/i2c/ov2640.c
> > @@ -1048,21 +1048,39 @@ static const struct v4l2_subdev_ops ov2640_subdev_ops = {
> >  static int ov2640_probe_dt(struct i2c_client *client,
> >  		struct ov2640_priv *priv)
> >  {
> > +	int ret;
> > +
> >  	/* Request the reset GPIO deasserted */
> >  	priv->resetb_gpio = devm_gpiod_get_optional(&client->dev, "resetb",
> >  			GPIOD_OUT_LOW);
> > -	if (!priv->resetb_gpio)
> > +	if (!priv->resetb_gpio) {
> >  		dev_dbg(&client->dev, "resetb gpio is not assigned!\n");
> > -	else if (IS_ERR(priv->resetb_gpio))
> > -		return PTR_ERR(priv->resetb_gpio);
> > +	} else {
> > +		ret = PTR_ERR(priv->resetb_gpio);
> > +
> > +		if (ret && ret != -ENOSYS) {
> > +			dev_dbg(&client->dev,
> > +				"Error %d while getting resetb gpio\n",
> > +				ret);
> > +			return ret;
> > +		}
> > +	}  
> 
> This would work. I just wish it'd look nicer. :-)
> 
> How about something like:
> 
> ret = PTR_ERR(priv->reset_gpio);
> if (!priv->reset_gpio) {
> 	dev_dbg("reset gpio is not assigned");
> } else if (ret != -ENOSYS) {
> 	dev_dbg("error %d while getting reset gpio, ret);

It still need to test if ret == 0, as otherwise it will do the wrong thing
here. 


I guess the patch below does the trick and it is not ugly :-)


> 	return ret;
> }
> 
> I prefer this option as it's not dependent on the system firmware type.

Thanks,
Mauro

[PATCH] ov2640: print error if devm_*_optional*() fails

devm_gpiod_get_optional() can return -ENOSYS if GPIOLIB is
disabled, causing probe to fail. Warn the user if this
happens.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

diff --git a/drivers/media/i2c/ov2640.c b/drivers/media/i2c/ov2640.c
index 4a2ae24f8722..8c87ed8306ea 100644
--- a/drivers/media/i2c/ov2640.c
+++ b/drivers/media/i2c/ov2640.c
@@ -765,17 +765,17 @@ static int ov2640_s_register(struct v4l2_subdev *sd,
 
 static int ov2640_s_power(struct v4l2_subdev *sd, int on)
 {
+#ifdef CONFIG_GPIOLIB
 	struct i2c_client *client = v4l2_get_subdevdata(sd);
 	struct ov2640_priv *priv = to_ov2640(client);
 
-#ifdef CONFIG_GPIOLIB
 	if (priv->pwdn_gpio)
 		gpiod_direction_output(priv->pwdn_gpio, !on);
 	if (on && priv->resetb_gpio) {
 		/* Active the resetb pin to perform a reset pulse */
 		gpiod_direction_output(priv->resetb_gpio, 1);
 		usleep_range(3000, 5000);
-		gpiod_direction_output(priv->resetb_gpio, 0);
+		gpiod_set_value(priv->resetb_gpio, 0);
 	}
 #endif
 	return 0;
@@ -1048,21 +1048,35 @@ static const struct v4l2_subdev_ops ov2640_subdev_ops = {
 static int ov2640_probe_dt(struct i2c_client *client,
 		struct ov2640_priv *priv)
 {
+	int ret;
+
 	/* Request the reset GPIO deasserted */
 	priv->resetb_gpio = devm_gpiod_get_optional(&client->dev, "resetb",
 			GPIOD_OUT_LOW);
+
 	if (!priv->resetb_gpio)
 		dev_dbg(&client->dev, "resetb gpio is not assigned!\n");
-	else if (IS_ERR(priv->resetb_gpio))
-		return PTR_ERR(priv->resetb_gpio);
+
+	ret = PTR_ERR_OR_ZERO(priv->pwdn_gpio);
+	if (ret && ret != -ENOSYS) {
+		dev_dbg(&client->dev,
+			"Error %d while getting resetb gpio\n", ret);
+		return ret;
+	}
 
 	/* Request the power down GPIO asserted */
 	priv->pwdn_gpio = devm_gpiod_get_optional(&client->dev, "pwdn",
 			GPIOD_OUT_HIGH);
+
 	if (!priv->pwdn_gpio)
 		dev_dbg(&client->dev, "pwdn gpio is not assigned!\n");
-	else if (IS_ERR(priv->pwdn_gpio))
-		return PTR_ERR(priv->pwdn_gpio);
+
+	ret = PTR_ERR_OR_ZERO(priv->pwdn_gpio);
+	if (ret && ret != -ENOSYS) {
+		dev_dbg(&client->dev,
+			"Error %d while getting pwdn gpio\n", ret);
+		return ret;
+	}
 
 	return 0;
 }