Thanks again:
On 8/25/21 4:05 AM, Andy Shevchenko wrote:
On Wed, Aug 25, 2021 at 1:09 AM Daniel Dadap <ddadap@xxxxxxxxxx> wrote:
A number of upcoming notebook computer designs drive the internal
display panel's backlight PWM through the Embedded Controller (EC).
This EC-based backlight control can be plumbed through to an ACPI
"WMAA" method interface, which in turn can be wrapped by WMI with
the GUID handle 603E9613-EF25-4338-A3D0-C46177516DB7.
Add a new driver, aliased to the WMAA WMI GUID, to expose a sysfs
backlight class driver to control backlight levels on systems with
EC-driven backlights.
I tried to avoid repetition of the comments given by others.
So, mine below.
...
+config WMAA_BACKLIGHT_WMI
+ tristate "ACPI WMAA Backlight Driver"
+ depends on ACPI_WMI
+ depends on BACKLIGHT_CLASS_DEVICE
+ help
+ This driver provides a sysfs backlight interface for notebook
+ systems which expose the WMAA ACPI method and an associated WMI
+ wrapper to drive LCD backlight levels through the system's
+ Embedded Controller.
Please, add a sentence to tell how the module will be called. There
are plenty of examples in the kernel.
...
+struct wmaa_args {
+ u32 set;
+ u32 val;
+ u32 ret;
+ u32 ignored[3];
+};
I guess this structure deserves a kernel doc.
Do you have a recommended location? From a quick skim I didn't see any
document in Documentation/ that seemed most appropriate to add this to.
...
+static const struct wmi_device_id wmaa_backlight_wmi_id_table[] = {
+ { .guid_string = WMAA_WMI_GUID },
+ { },
No comma for termination.
+};
...
+static int wmaa_backlight_get_brightness(struct backlight_device *bd)
+{
+ u32 level;
+ int ret;
+
+ ret = wmaa_get_brightness(&level);
+ WARN_ON(ret != 0);
Why?
To differentiate a 0 because the level is actually 0 versus a 0 because
there was an error. The backlight device API doesn't seem to have a way
to report errors.
+ return ret == 0 ? level : 0;
+}
...
+static int wmaa_backlight_wmi_probe(struct wmi_device *w, const void *ctx)
+{
+ struct backlight_properties props = {0};
{} is slightly better.
+ struct wmi_wmaa_priv *priv;
+ u32 source;
+ int ret;
+
+ priv = devm_kmalloc(&w->dev, sizeof(*priv), GFP_KERNEL);
+ if(!priv)
+ return -ENOMEM;
+ wdev = w;
I'm wondering if it's possible to avoid having a global variable.
It is; this can be stored in the struct backlight_device.
+ ret = wmaa_get_brightness_source(&source);
+ if (ret)
+ goto done;
+
+ if (source != WMAA_SOURCE_EC) {
+ ret = -ENODEV;
+ goto done;
+ }
+
+ // Register a backlight handler
+ props.type = BACKLIGHT_PLATFORM;
+ ret = wmaa_get_max_brightness(&props.max_brightness);
+ if (ret)
+ goto done;
+
+ ret = wmaa_get_brightness(&props.brightness);
+ if (ret)
+ goto done;
+
+ priv->backlight = backlight_device_register("wmaa_backlight",
+ NULL, NULL, &wmaa_backlight_ops, &props);
+ if (IS_ERR(priv->backlight))
+ return PTR_ERR(priv->backlight);
+
+ dev_set_drvdata(&w->dev, priv);
+done:
Useless. Return directly.
Yeah, most likely there used to be some other cleanup here. Thanks.
+ return ret;
+}
...
+static struct wmi_driver wmaa_backlight_wmi_driver = {
+ .driver = {
+ .name = "wmaa-backlight",
+ },
+ .probe = wmaa_backlight_wmi_probe,
+ .remove = wmaa_backlight_wmi_remove,
+ .id_table = wmaa_backlight_wmi_id_table,
+};
+
Redundant blank line.
+module_wmi_driver(wmaa_backlight_wmi_driver);
...
+
+MODULE_ALIAS("wmi:"WMAA_WMI_GUID);
Can you move this closer to GUID? But I'm not sure what is the
preferred style. Hans?
I'll do whatever is most stylistically preferred.
