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Document composite driver workaround

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This commit is contained in:
Larry Snizek
2019-08-07 10:48:25 +01:00
parent ee5e1095c2
commit e56af33aa3
1 changed files with 16 additions and 1 deletions
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17
lib_xua/src/core/endpoint0/xua_ep0_descriptors.h
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@@ -414,7 +414,22 @@ USB_Descriptor_Device_t devDesc_Audio1 =
#endif
#if (AUDIO_CLASS == 2)
/* Device Descriptor for Audio Class 2.0 (Assumes High-Speed ) */
/* Device Descriptor for Audio Class 2.0 (Assumes High-Speed )
*
* The use of two configurations dates back to Windows XP (could be SP2). This
* lacked some standards support and incorrectly parsed the full audio class 2.0
* descriptor with its IADs (Interface Association Descriptors). The observed
* behaviour included loading the built-in audio class 1.0 driver on some
* interfaces (possibly the wrong ones, too), and hanging.
*
* Presenting a blank configuration first prevented loading the composite driver
* and issues arising from it, while still allowing to load a vendor driver on
* the actual configuration.
*
* Recent Windows subsystem can parse our class 2.0 descriptor correctly
* (certainly Windows 7 and onwards). It may be possible to remove this
* workaround.
*/
USB_Descriptor_Device_t devDesc_Audio2 =
{
.bLength = sizeof(USB_Descriptor_Device_t),