This is a note to let you know that I've just added the patch titled spi: stm32: properly handle 0 byte transfer to the 5.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: spi-stm32-properly-handle-0-byte-transfer.patch and it can be found in the queue-5.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 96edd8702a6e9a649aeffcf6c35b4262f1390292 Author: Alain Volmat <alain.volmat@xxxxxxxxxxx> Date: Fri Feb 5 19:59:25 2021 +0100 spi: stm32: properly handle 0 byte transfer [ Upstream commit 2269f5a8b1a7b38651d62676b98182828f29d11a ] On 0 byte transfer request, return straight from the xfer function after finalizing the transfer. Fixes: dcbe0d84dfa5 ("spi: add driver for STM32 SPI controller") Signed-off-by: Alain Volmat <alain.volmat@xxxxxxxxxxx> Link: https://lore.kernel.org/r/1612551572-495-2-git-send-email-alain.volmat@xxxxxxxxxxx Signed-off-by: Mark Brown <broonie@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/drivers/spi/spi-stm32.c b/drivers/spi/spi-stm32.c index 6017209c6d2f7..6eeb39669a866 100644 --- a/drivers/spi/spi-stm32.c +++ b/drivers/spi/spi-stm32.c @@ -1677,6 +1677,10 @@ static int stm32_spi_transfer_one(struct spi_master *master, struct stm32_spi *spi = spi_master_get_devdata(master); int ret; + /* Don't do anything on 0 bytes transfers */ + if (transfer->len == 0) + return 0; + spi->tx_buf = transfer->tx_buf; spi->rx_buf = transfer->rx_buf; spi->tx_len = spi->tx_buf ? transfer->len : 0;