Re: [PATCH 2/3] tegra: pwm-backlight: add tegra pwm-bl driver

On 01/19/2013 03:30 AM, Alexandre Courbot wrote:

Add a PWM-backlight subdriver for Tegra boards, with support for
Ventana.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
---
 arch/arm/boot/dts/tegra20-ventana.dts  |  18 +++-
 arch/arm/configs/tegra_defconfig       |   1 +
 drivers/video/backlight/Kconfig        |   7 ++
 drivers/video/backlight/pwm_bl.c       |   3 +
 drivers/video/backlight/pwm_bl_tegra.c | 159 +++++++++++++++++++++++++++++++++

This should be at least 3 separate patches: (1) Driver code (2) Ventana
.dts file (3) Tegra defconfig.

+	backlight {
+		compatible = "pwm-backlight-ventana";

If this is Ventana-specific, this should have a vendor prefix; "nvidia,"
would be appropriate.

But, why is this Ventana-specific; surely it's at most panel-specific,
or perhaps even generic across any/most LCD panels?

There needs to be binding documentation.

+		brightness-levels = <0 16 32 48 64 80 96 112 128 144 160 176 192 208 224 240 255>;
+		default-brightness-level = <12>;
+
+		pwms = <&pwm 2 5000000>;
+		pwm-names = "backlight";
+
+		power-supply = <&vdd_bl_reg>;

"power" doesn't seem like a good regulator name; power to what? Is this
for the backlight, since I see there's a panel-supply below?

+		panel-supply = <&vdd_pnl_reg>;

+		bl-gpio = <&gpio 28 0>;
+		bl-panel = <&gpio 10 0>;

GPIO names usually have "gpios" in their name, so I assume those should
be bl-enable-gpios, panel-enable-gpios?

+static void exit_ventana(struct device *dev)
+{
+	struct ventana_bl_data *data = pwm_backlight_get_subdriver_data(dev);
+
+	devm_gpio_free(dev, data->panel_gpio);
+	devm_gpio_free(dev, data->bl_gpio);
+	devm_regulator_put(data->vdd_panel);
+	devm_regulator_put(data->vdd_power);
+	devm_kfree(dev, data);
+}

There shouldn't be a need to explicitly free devm-allocated objects in
almost all cases; that's the whole point of the devm APIs.

+static struct pwm_backlight_subdriver pwm_backlight_ventana_subdriver = {
+	.name = "pwm-backlight-ventana",
+	.init = init_ventana,
+	.exit = exit_ventana,
+	.notify = notify_ventana,
+	.notify_after = notify_after_ventana,
+};

It seems like all of that code should be completely generic.

+static int __init pwm_backlight_tegra_init(void)
+{
+	pwm_backlight_add_subdriver(&pwm_backlight_ventana_subdriver);
+	return 0;
+}
+
+static void __exit pwm_backlight_tegra_exit(void)
+{
+	pwm_backlight_remove_subdriver(&pwm_backlight_ventana_subdriver);
+}
+
+module_init(pwm_backlight_tegra_init);
+module_exit(pwm_backlight_tegra_exit);

Rather than invent some new registration mechanism, if we need
board-/panel-/...-specific drivers, it'd be better to make each of those
specific drivers a full platform device in an of itself (i.e. regular
Linux platform device/driver, have its own probe(), etc.), and have
those specific drivers call into the base PWM backlight code, treating
it like a utility API.

+MODULE_DESCRIPTION("Backlight Driver for Tegra boards");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:pwm-tegra-backlight");
+
+

Some extra blank lines there.