Re: [PATCH 3/6] backlight/pandora: Stop using BL_CORE_DRIVER1

[Daniel Thompson]

On 17/01/18 21:38, Daniel Vetter wrote:
> Thanks a lot for your comments.
>
> On Wed, Jan 17, 2018 at 04:47:41PM +0000, Daniel Thompson wrote:
> > On 17/01/18 14:01, Daniel Vetter wrote:
> > > Leaking driver internal tracking into the already massively confusing
> > > backlight power tracking is really confusing.
> > >
> > > Stop that by allocating a tiny driver private data structure instead.
> > >
> > > Cc: Lee Jones <lee.jones@xxxxxxxxxx>
> > > Cc: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
> > > Cc: Jingoo Han <jingoohan1@xxxxxxxxx>
> > > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
> > > ---
> > >    drivers/video/backlight/pandora_bl.c | 26 +++++++++++++++++++-------
> > >    1 file changed, 19 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/drivers/video/backlight/pandora_bl.c b/drivers/video/backlight/pandora_bl.c
> > > index a186bc677c7d..6bd159946a47 100644
> > > --- a/drivers/video/backlight/pandora_bl.c
> > > +++ b/drivers/video/backlight/pandora_bl.c
> > > @@ -35,11 +35,15 @@
> > >    #define MAX_VALUE 63
> > >    #define MAX_USER_VALUE (MAX_VALUE - MIN_VALUE)
> > > -#define PANDORABL_WAS_OFF BL_CORE_DRIVER1
> > > +struct pandora_private {
> > > +	unsigned old_state;
> > > +#define PANDORABL_WAS_OFF 1
> >
> > Nit, but we using old_state like a bitfield so, BIT(0)?
> >
> >
> > > +};
> > >    static int pandora_backlight_update_status(struct backlight_device *bl)
> > >    {
> > >    	int brightness = bl->props.brightness;
> > > +	struct pandora_private *priv = bl_get_data(bl);
> > >    	u8 r;
> > >    	if (bl->props.power != FB_BLANK_UNBLANK)
> > > @@ -53,7 +57,7 @@ static int pandora_backlight_update_status(struct backlight_device *bl)
> > >    		brightness = MAX_USER_VALUE;
> > >    	if (brightness == 0) {
> > > -		if (bl->props.state & PANDORABL_WAS_OFF)
> > > +		if (priv->old_state & PANDORABL_WAS_OFF)
> > >    			goto done;
> > >    		/* first disable PWM0 output, then clock */
> > > @@ -66,7 +70,7 @@ static int pandora_backlight_update_status(struct backlight_device *bl)
> > >    		goto done;
> > >    	}
> > > -	if (bl->props.state & PANDORABL_WAS_OFF) {
> > > +	if (priv->old_state & PANDORABL_WAS_OFF) {
> > >    		/*
> > >    		 * set PWM duty cycle to max. TPS61161 seems to use this
> > >    		 * to calibrate it's PWM sensitivity when it starts.
> > > @@ -93,9 +97,9 @@ static int pandora_backlight_update_status(struct backlight_device *bl)
> > >    done:
> > >    	if (brightness != 0)
> > > -		bl->props.state &= ~PANDORABL_WAS_OFF;
> > > +		priv->old_state 0;
> > >    	else
> > > -		bl->props.state |= PANDORABL_WAS_OFF;
> > > +		priv->old_state = PANDORABL_WAS_OFF;
> >
> > Well, we were using it like a bitfield until this bit...
>
> I had a simple boolean first (because that's all we neeed), but that made
> the code less readable. Should I s/1/true/ in the #define? The entire C99
> bool tends to be a bit a bikeshed sometimes :-)

I'd prefer a simple boolean or just storing old_brightness directly in 
priv... it is only ever consumed as a boolean anyway. I'd have to say 
I'm not keen on #define true alongside the existing bitmask checks.

However... I'm happy to leave that with you. Providing the spurious 
kfree() is removed then please feel free to repost with:

Acked-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>


Daniel.





> > >    	return 0;
> > >    }
> > > @@ -109,15 +113,23 @@ static int pandora_backlight_probe(struct platform_device *pdev)
> > >    {
> > >    	struct backlight_properties props;
> > >    	struct backlight_device *bl;
> > > +	struct pandora_private *priv;
> > >    	u8 r;
> > > +	priv = devm_kmalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
> > > +	if (!priv) {
> > > +		dev_err(&pdev->dev, "failed to allocate driver private data\n");
> > > +		return -ENOMEM;
> > > +	}
> > > +
> > >    	memset(&props, 0, sizeof(props));
> > >    	props.max_brightness = MAX_USER_VALUE;
> > >    	props.type = BACKLIGHT_RAW;
> > >    	bl = devm_backlight_device_register(&pdev->dev, pdev->name, &pdev->dev,
> > > -					NULL, &pandora_backlight_ops, &props);
> > > +					priv, &pandora_backlight_ops, &props);
> > >    	if (IS_ERR(bl)) {
> > >    		dev_err(&pdev->dev, "failed to register backlight\n");
> > > +		kfree(priv);
> >
> > Why can't we rely on devres for cleanup?
>
> Argh, I had kmalloc first and then changed to devm_kmalloc. The kfree here
> needs to go indeed.
>
> Cheers, Daniel
>
> > >    		return PTR_ERR(bl);
> > >    	}
> > > @@ -126,7 +138,7 @@ static int pandora_backlight_probe(struct platform_device *pdev)
> > >    	/* 64 cycle period, ON position 0 */
> > >    	twl_i2c_write_u8(TWL_MODULE_PWM, 0x80, TWL_PWM0_ON);
> > > -	bl->props.state |= PANDORABL_WAS_OFF;
> > > +	priv->old_state = PANDORABL_WAS_OFF;
> > >    	bl->props.brightness = MAX_USER_VALUE;
> > >    	backlight_update_status(bl);