> On 25 Feb 2025, at 4:03 PM, andriy.shevchenko@xxxxxxxxxxxxxxx wrote:
>
> On Tue, Feb 25, 2025 at 10:09:42AM +0000, Aditya Garg wrote:
>> From: Kerem Karabay <kekrby@xxxxxxxxx>
>>
>> The Touch Bars found on x86 Macs support two USB configurations: one
>> where the device presents itself as a HID keyboard and can display
>> predefined sets of keys, and one where the operating system has full
>> control over what is displayed.
>>
>> This commit adds support for the display functionality of the second
>> configuration. Functionality for the first configuration has been
>> merged in the HID tree.
>>
>> Note that this driver has only been tested on T2 Macs, and only includes
>> the USB device ID for these devices. Testing on T1 Macs would be
>> appreciated.
>>
>> Credit goes to Ben (Bingxing) Wang on GitHub for reverse engineering
>> most of the protocol.
>>
>> Also, as requested by Andy, I would like to clarify the use of __packed
>> structs in this driver:
>>
>> - All the packed structs are aligned except for appletbdrm_msg_information.
>> - We have to pack appletbdrm_msg_information since it is requirement of
>> the protocol.
>> - We compared binaries compiled by keeping the rest structs __packed and
>> not __packed using bloat-o-meter, and __packed was not affecting code
>> generation.
>> - To maintain consistency, rest structs have been kept __packed.
>>
>> I would also like to point out that since the driver was reverse-engineered
>> the actual data types of the protocol might be different, including, but
>> not limited to, endianness.
>
> ...
>
>> +static int appletbdrm_probe(struct usb_interface *intf,
>> + const struct usb_device_id *id)
>> +{
>> + struct usb_endpoint_descriptor *bulk_in, *bulk_out;
>> + struct device *dev = &intf->dev;
>> + struct appletbdrm_device *adev;
>> + struct drm_device *drm;
>> + int ret;
>> +
>> + ret = usb_find_common_endpoints(intf->cur_altsetting, &bulk_in, &bulk_out, NULL, NULL);
>> + if (ret) {
>> + drm_err(drm, "Failed to find bulk endpoints\n");
>
> This is simply wrong (and in this case even lead to crash in some circumstances).
> drm_err() may not be used here. That's my point in previous discussions.
> Independently on the subsystem the ->probe() for the sake of consistency and
> being informative should only rely on struct device *dev,
>
I'm not sure how drm_err works, but struct drm_device does have a struct device *dev as well. Anyways, this is something I'll leave for Thomas to reply.
