spi: ch341: handle transfers without a TX or RX buffer

ch341_transfer_one() unconditionally copies from trans->tx_buf into the
TX packet and hands trans->rx_buf to usb_bulk_msg() for the readback.

The SPI core allows half-duplex transfers where either of the buffers
is NULL, so a transfer without TX data crashes the kernel on the memcpy
and a transfer without RX data makes usb_bulk_msg() store the received
data at address 0.

The CH341A clocks data in both directions on every transfer; there is
no mode to disable a direction. Set SPI_CONTROLLER_MUST_TX and
SPI_CONTROLLER_MUST_RX so the SPI core fills in dummy buffers for
half-duplex transfers.

Fixes: 8846739f52af ("spi: add ch341a usb2spi driver")
Cc: stable@vger.kernel.org # 6.11+
Signed-off-by: Weibin Liu <liuwb@xiaopeng.com>
Link: https://patch.msgid.link/20261013054339.77477-1-liuwb@xiaopeng.com
Signed-off-by: Mark Brown <broonie@kernel.org>

0 files changed, 0 insertions, 0 deletions