4afd728769
Implement a local bounce buffer for private I3C SDR and I2C transfers
when using DMA and the buffer attached to the transfer is not DMA safe.
Otherwise the DMA transfer will fail and with following warning:
[ 11.411059] i3c mipi-i3c-hci.0: rejecting DMA map of vmalloc memory
[ 11.417313] WARNING: CPU: 3 PID: 357 at include/linux/dma-mapping.h:332 hci_dma_queue_xfer+0x2e2/0x300 [mipi_i3c_hci]
Strictly speaking private I3C SDR transfers are expected to pass a
DMA-able buffer. However I fear this requirement may easily be slipped
or go unnoticed when I3C interface support is added into a existing
device driver that use regmap API to read/write stack variables.
For example this is the case with the commit
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Linux kernel
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