> On 25 Feb 2025, at 8:24 PM, Aditya Garg <gargaditya08@xxxxxxxx> wrote:
>
>
>
>> On 25 Feb 2025, at 5:28 PM, Thomas Zimmermann <tzimmermann@xxxxxxx> wrote:
>>
>> Hi
>>
>>> Am 25.02.25 um 11:33 schrieb andriy.shevchenko@xxxxxxxxxxxxxxx:
>>>>> 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,
>>
>> That's never going to work with DRM. There's so much code in a DRM probe function that uses the DRM error functions.
>>
>> This specific instance here is wrong, as the drm pointer hasn't been initialized. But as soon as it is, it's much better to use drm_err() and friends. It will do the right thing and give consistent output across drivers.
>>
> Ok so this is actually an interesting case, since I am trying to fix it. To initialise the drm pointer, we need to initialise adev, and to initialise adev, we need to run usb_find_common_endpoints first. So IMO, we cannot use drm_err here, but rather dev_err_probe can be used.
Infact dev is also not initialised......
>>
>>
>>>
>>>> + return ret;
>>>> + }
>>>> +
>>>> + adev = devm_drm_dev_alloc(dev, &appletbdrm_drm_driver, struct appletbdrm_device, drm);
>>>> + if (IS_ERR(adev))
>>>> + return PTR_ERR(adev);
>>>> +
>>>> + adev->in_ep = bulk_in->bEndpointAddress;
>>>> + adev->out_ep = bulk_out->bEndpointAddress;
>>>> + adev->dmadev = dev;
>>>> +
>>>> + drm = &adev->drm;
>>>> +
>>>> + usb_set_intfdata(intf, adev);
>>>> +
>>>> + ret = appletbdrm_get_information(adev);
>>>> + if (ret) {
>>>> + drm_err(drm, "Failed to get display information\n");
>>>> + return ret;
>>>> + }
>>>> +
>>>> + ret = appletbdrm_signal_readiness(adev);
>>>> + if (ret) {
>>>> + drm_err(drm, "Failed to signal readiness\n");
>>>> + return ret;
>>>> + }
>>>> +
>>>> + ret = appletbdrm_setup_mode_config(adev);
>>>> + if (ret) {
>>>> + drm_err(drm, "Failed to setup mode config\n");
>>>> + return ret;
>>>> + }
>>>> +
>>>> + ret = drm_dev_register(drm, 0);
>>>> + if (ret) {
>>>> + drm_err(drm, "Failed to register DRM device\n");
>>>> + return ret;
>>>> + }
>>>> +
>>>> + ret = appletbdrm_clear_display(adev);
>>>> + if (ret) {
>>>> + drm_err(drm, "Failed to clear display\n");
>>>> + return ret;
>>>> + }
>>>> +
>>>> + return 0;
>>>> +}
>>
>> --
>> --
>> Thomas Zimmermann
>> Graphics Driver Developer
>> SUSE Software Solutions Germany GmbH
>> Frankenstrasse 146, 90461 Nuernberg, Germany
>> GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
>> HRB 36809 (AG Nuernberg)
>>
