Re: [PATCH 7/8] fbdev: ssd1307fb: Add sysfs handles to expose contrast and dim setting to userspace.

["Thomas Niederprüm" <niederp@physik.uni-kl.de>]

Am Sat, 7 Feb 2015 12:43:29 +0100
schrieb Maxime Ripard <maxime.ripard@free-electrons.com>:

> On Fri, Feb 06, 2015 at 11:28:13PM +0100, niederp@physik.uni-kl.de
> wrote:
> > From: Thomas Niederprüm <niederp@physik.uni-kl.de>
> > 
> > This patch adds sysfs handles to enable userspace control over the
> > display contrast as well as the dim mode. The handles are available
> > as "contrast" and "dim" in the framebuffers sysfs domain.
> > 
> > Signed-off-by: Thomas Niederprüm <niederp@physik.uni-kl.de>
> > ---
> >  drivers/video/fbdev/ssd1307fb.c | 88
> > ++++++++++++++++++++++++++++++++++++++++- 1 file changed, 87
> > insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/video/fbdev/ssd1307fb.c
> > b/drivers/video/fbdev/ssd1307fb.c index b38315d..02931c7 100644
> > --- a/drivers/video/fbdev/ssd1307fb.c
> > +++ b/drivers/video/fbdev/ssd1307fb.c
> > @@ -33,6 +33,7 @@
> >  #define SSD1307FB_CONTRAST		0x81
> >  #define	SSD1307FB_CHARGE_PUMP		0x8d
> >  #define SSD1307FB_SEG_REMAP_ON		0xa1
> > +#define SSD1307FB_DISPLAY_DIM		0xac
> >  #define SSD1307FB_DISPLAY_OFF		0xae
> >  #define SSD1307FB_SET_MULTIPLEX_RATIO	0xa8
> >  #define SSD1307FB_DISPLAY_ON		0xaf
> > @@ -43,6 +44,9 @@
> >  #define	SSD1307FB_SET_COM_PINS_CONFIG	0xda
> >  #define	SSD1307FB_SET_VCOMH		0xdb
> >  
> > +#define MIN_CONTRAST 0
> > +#define MAX_CONTRAST 255
> > +
> >  #define BITSPERPIXEL 1
> >  #define DELAYDIVIDER 20
> >  
> > @@ -69,6 +73,7 @@ struct ssd1307fb_par {
> >  	u32 dclk_div;
> >  	u32 dclk_frq;
> >  	struct ssd1307fb_deviceinfo *device_info;
> > +	u32 dim;
> >  	struct i2c_client *client;
> >  	u32 height;
> >  	struct fb_info *info;
> > @@ -515,6 +520,79 @@ static const struct of_device_id
> > ssd1307fb_of_match[] = { };
> >  MODULE_DEVICE_TABLE(of, ssd1307fb_of_match);
> >  
> > +static ssize_t show_contrast(struct device *device,
> > +			   struct device_attribute *attr, char
> > *buf) +{
> > +	struct fb_info *info = dev_get_drvdata(device);
> > +	struct ssd1307fb_par *par = info->par;
> > +
> > +	return snprintf(buf, PAGE_SIZE, "%d\n", par->contrast);
> > +}
> > +
> > +static ssize_t store_contrast(struct device *device,
> > +			    struct device_attribute *attr,
> > +			    const char *buf, size_t count)
> > +{
> > +	struct fb_info *info = dev_get_drvdata(device);
> > +	struct ssd1307fb_par *par = info->par;
> > +	unsigned long contrastval;
> > +	int ret;
> > +
> > +	ret = kstrtoul(buf, 0, &contrastval);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	par->contrast = max(min(contrastval,
> > +		(ulong)MAX_CONTRAST), (ulong)MIN_CONTRAST);
> > +
> > +	ret = ssd1307fb_write_cmd(par->client, SSD1307FB_CONTRAST);
> > +	ret = ret & ssd1307fb_write_cmd(par->client,
> > par->contrast);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	return count;
> > +}
> > +
> > +
> > +static ssize_t show_dim(struct device *device,
> > +			   struct device_attribute *attr, char
> > *buf) +{
> > +	struct fb_info *info = dev_get_drvdata(device);
> > +	struct ssd1307fb_par *par = info->par;
> > +
> > +	return snprintf(buf, PAGE_SIZE, "%d\n", par->dim);
> > +}
> > +
> > +static ssize_t store_dim(struct device *device,
> > +			    struct device_attribute *attr,
> > +			    const char *buf, size_t count)
> > +{
> > +	struct fb_info *info = dev_get_drvdata(device);
> > +	struct ssd1307fb_par *par = info->par;
> > +	unsigned long dimval;
> > +	int ret;
> > +
> > +	ret = kstrtoul(buf, 0, &dimval);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	par->dim = max(min(dimval, (ulong)1), (ulong)0);
> > +	if (par->dim)
> > +		ret = ssd1307fb_write_cmd(par->client,
> > SSD1307FB_DISPLAY_DIM);
> > +	else
> > +		ret = ssd1307fb_write_cmd(par->client,
> > SSD1307FB_DISPLAY_ON);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	return count;
> > +}
> > +
> > +static struct device_attribute device_attrs[] = {
> > +	__ATTR(contrast, S_IRUGO|S_IWUSR, show_contrast,
> > store_contrast),
> > +	__ATTR(dim, S_IRUGO|S_IWUSR, show_dim, store_dim),
> > +
> > +};
> > +
> 
> I would have thought this was something accessible through the
> framebuffer ioctl.
> 
> Apparently it's not, at least for the contrast, so maybe it should be
> added there, instead of doing it for a single driver?

I think the contrast setting for an OLED display is much like the
backlight setting for LCD panel. Since there is also no ioctl to set
the backlight of an LCD I wonder if the contrast of an OLED should have
one.

> 
> (oh, and btw, every sysfs file should be documented in
> Documentation/ABI)
> 
> >  static int ssd1307fb_probe(struct i2c_client *client,
> >  			   const struct i2c_device_id *id)
> >  {
> > @@ -523,7 +601,7 @@ static int ssd1307fb_probe(struct i2c_client
> > *client, u32 vmem_size;
> >  	struct ssd1307fb_par *par;
> >  	u8 *vmem;
> > -	int ret;
> > +	int ret, i;
> >  
> >  	if (!node) {
> >  		dev_err(&client->dev, "No device tree data
> > found!\n"); @@ -650,6 +728,14 @@ static int ssd1307fb_probe(struct
> > i2c_client *client, goto reset_oled_error;
> >  
> >  	ret = register_framebuffer(info);
> > +
> > +	for (i = 0; i < ARRAY_SIZE(device_attrs); i++)
> > +		ret = device_create_file(info->dev,
> > &device_attrs[i]); +
> > +	if (ret) {
> > +		dev_err(&client->dev, "Couldn't register sysfs
> > nodes\n");
> > +	}
> > +
> 
> sysfs_create_groups does pretty much that already.

I'll have a look at it.

> 
> And don't forget to remove these files in the .remove()

Good point! :)

> 
> >  	if (ret) {
> >  		dev_err(&client->dev, "Couldn't register the
> > framebuffer\n"); goto panel_init_error;
> > -- 
> > 2.1.1
> > 
> 
> Maxime
>