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Based on the reality[1][2] that vb2_dma_sg_alloc() can't alloc buffer with device DMA limits, those device will always get below error: "swiotlb buffer is full (sz: 393216 bytes), total 65536 (slots), used 2358 (slots)" and the uvc gadget function can't work at all. The videobuf2-dma-sg.c driver doesn't has a formal improve about this issue till now. For UVC gadget, the videobuf2 subsystem doesn't do dma_map() on vmalloc returned big buffer when allocate the video buffers, however, it do it for dma_sg returned buffer. So the issue happens for vb2_dma_sg_alloc(). To workaround the issue, lets retry vb2_reqbufs() with vb_vmalloc_memops if it fails to allocate buffer with vb2_dma_sg_memops. If use vmalloced buffer, UVC gadget will allocate some small buffers for each usb_request to do dma transfer, then uvc driver will memcopy data from big buffer to small buffer. Link[1]: https://lore.kernel.org/linux-media/20230828075420.2009568-1-anle.pan@nxp.com/ Link[2]: https://lore.kernel.org/linux-media/20230914145812.12851-1-hui.fang@nxp.com/ Signed-off-by: Xu Yang <xu.yang_2@nxp.com> Reviewed-by: Frank Li <Frank.Li@nxp.com> Link: https://patch.msgid.link/20260113-uvc-gadget-fix-patch-v2-4-62950ef5bcb5@nxp.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>