Re: [PATCH 4/5] HID: apple-ibridge: Add Apple iBridge HID driver for T1 chip.
From: Jonathan Cameron
Date: Sun Feb 28 2021 - 10:05:13 EST
On 2021年2月27日 17:26:42 -0800
Ronald Tschalär <ronald@xxxxxxxxxxxxx> wrote:
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The iBridge device provides access to several devices, including:
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- the Touch Bar
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- the iSight webcam
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- the light sensor
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- the fingerprint sensor
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This driver provides the core support for managing the iBridge device
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and the access to the underlying devices. In particular, the
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functionality for the touch bar and light sensor is exposed via USB HID
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interfaces, and on devices with the T1 chip one of the HID devices is
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used for both functions. So this driver creates virtual HID devices, one
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per top-level report collection on each HID device (for a total of 3
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virtual HID devices). The sub-drivers then bind to these virtual HID
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devices.
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This way the Touch Bar and ALS drivers can be kept in their own modules,
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while at the same time making them look very much like as if they were
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connected to the real HID devices. And those drivers then work (mostly)
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without further changes on MacBooks with the T2 chip that don't need
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this driver.
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Signed-off-by: Ronald Tschalär <ronald@xxxxxxxxxxxxx>
Hi Ronald.
This is far from my specialty but mostly looks sensible to me.
Just one thing stood out that I couldn't understand. See below.
Jonathan
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new file mode 100644
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index 0000000000000..5f2b71c199746
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--- /dev/null
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+++ b/drivers/hid/apple-ibridge.c
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@@ -0,0 +1,682 @@
...
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+
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+#ifdef CONFIG_PM
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+/**
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+ * appleib_forward_int_op() - Forward a hid-driver callback to all drivers on
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+ * all virtual HID devices attached to the given real HID device.
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+ * @hdev the real hid-device
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+ * @forward a function that calls the callback on the given driver
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+ * @args arguments for the forward function
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+ *
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+ * This is for callbacks that return a status as an int.
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+ *
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+ * Returns: 0 on success, or the first error returned by the @forward function.
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+ */
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+static int appleib_forward_int_op(struct hid_device *hdev,
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+ int (*forward)(struct hid_driver *,
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+ struct hid_device *, void *),
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+ void *args)
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+{
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+ struct appleib_hid_dev_info *hdev_info = hid_get_drvdata(hdev);
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+ struct hid_device *sub_hdev;
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+ int rc = 0;
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+ int i;
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+
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+ for (i = 0; i < ARRAY_SIZE(hdev_info->sub_hdevs); i++) {
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+ sub_hdev = hdev_info->sub_hdevs[i];
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+ if (sub_hdev->driver) {
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+ rc = forward(sub_hdev->driver, sub_hdev, args);
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+ if (rc)
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+ break;
return rc; here would be cleaner.
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+ }
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+
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+ break;
This is unusual. It's a for loop but as far as I can see only first iteration
can ever run as we exit the loop at this break if we haven't done so earlier.
What is the intent here?
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+ }
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+
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+ return rc;
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+}