On 03/14/2012 09:56 AM, Thierry Reding wrote:
> This commit adds very basic support for device tree probing. Currently,
> only a PWM and a list of distinct brightness levels can be specified.
> Enabling or disabling backlight power via GPIOs is not yet supported.
>
> A pointer to the exit() callback is stored in the driver data to keep it
> around until the driver is unloaded.
> +++ b/Documentation/devicetree/bindings/video/backlight/pwm-backlight
> +pwm-backlight bindings
> +
> +Required properties:
> + - compatible: "pwm-backlight"
> + - pwm: OF device-tree PWM specification
> + - num-brightness-levels: number of distinct brightness levels
> + - brightness-levels: array of distinct brightness levels
I assume the values in this array are 0 (darkest/off) to 255 (max
brightness)? The doc should probably specify this.
> + - default-brightness-level: the default brightness level
Likewise, this is an index into the default-brightness-level? Again,
it'd be best to explicitly state this.
...
> + brightness-levels = <0 4 8 16 32 64 128 255>;
> + default-brightness-level = <6>;
> +static int pwm_backlight_parse_dt(struct device *dev,
> + struct platform_pwm_backlight_data *data)
...
> + ret = of_property_read_u32(node, "default-brightness-level",
> + &value);
> + if (ret < 0)
> + goto free;
Range-check that against max_brightness?
> static int pwm_backlight_probe(struct platform_device *pdev)
...
> - pb->pwm = pwm_request(data->pwm_id, "backlight");
> - if (IS_ERR(pb->pwm)) {
> - dev_err(&pdev->dev, "unable to request PWM for backlight\n");
> - ret = PTR_ERR(pb->pwm);
> - goto err_alloc;
> - } else
> - dev_dbg(&pdev->dev, "got pwm for backlight\n");
> + if (!pb->pwm) {
> + pb->pwm = pwm_request(data->pwm_id, "backlight");
> + if (IS_ERR(pb->pwm)) {
> + dev_err(&pdev->dev, "unable to request PWM for backlight\n");
> + ret = PTR_ERR(pb->pwm);
> + goto err_alloc;
> + } else
> + dev_dbg(&pdev->dev, "got pwm for backlight\n");
> + }
Hmmm. It'd be more consistent if pwm_backlight_parse_dt() called
something like of_pwm_get() instead of of_pwm_request(), so that this
code could always call pwm_request() on the PWM and hence operate the
same irrespective of DT vs non-DT. GPIOs work that way at least.
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