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spi: virtio: Use the per-transfer bits per word

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virtio_spi_transfer_one() puts spi->bits_per_word into the request
header, so a transfer that sets its own word size reaches the backend
with the device default instead. The SPI core has already copied that
default into xfer->bits_per_word when the transfer leaves it at zero,
the same way it does for xfer->speed_hz, which this function already
uses.

Per-transfer word sizes are ordinary SPI usage. mipi_dbi, for one, sends
a 9-bit command and reads the reply as 8-bit data in the same message.
With a 16-bit device default, a one-byte transfer asking for 8 bits goes
out as a partial 16-bit word, which the backend may reject.

Fixes: f98cabe3f6 ("SPI: Add virtio SPI driver")
Cc: stable@vger.kernel.org
Assisted-by: LLM
Signed-off-by: Hao-Qun Huang <alvinhuang0603@gmail.com>
Link: https://patch.msgid.link/20260913032049.11209.alvinhuang0603@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Hao-Qun Huang 2026-09-13 03:20:49 +08:00 committed by Mark Brown
parent 930a7312c9
commit 095858324f
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1 changed files with 1 additions and 1 deletions
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2
drivers/spi/spi-virtio.c
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@ -168,7 +168,7 @@ static int virtio_spi_transfer_one(struct spi_controller *ctrl,
/* Fill struct spi_transfer_head */
th->chip_select_id = spi_get_chipselect(spi, 0);
th->bits_per_word = spi->bits_per_word;
th->bits_per_word = xfer->bits_per_word;
th->cs_change = xfer->cs_change;
th->tx_nbits = xfer->tx_nbits;
th->rx_nbits = xfer->rx_nbits;