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Commit 38ec10f6 authored by Mark Brown's avatar Mark Brown
Browse files

spi: Only call transfer_one() if we have buffers to transfer 



Client drivers such as the ChomeOS EC driver sometimes use transfers with
no buffers and only a delay specified in order to allow a delay after the
assertion of /CS. Rather than require controller drivers handle this noop
case gracefully put checks in the core to ensure that we don't call into
the controller for such transfers.

Reported-by: default avatarAddy Ke <addy.ke@rock-chips.com>
Tested-by: default avatarDoug Anderson <dianders@chromium.org>
Reviewed-by: default avatarDoug Anderson <dianders@chromium.org>
Signed-off-by: default avatarMark Brown <broonie@linaro.org>
parent 7d1311b9

drivers/spi/spi.c

+26 −18
Original line number Diff line number Diff line
@@ -789,6 +789,7 @@ static int spi_transfer_one_message(struct spi_master *master, 
	list_for_each_entry(xfer, &msg->transfers, transfer_list) {

		trace_spi_transfer_start(msg, xfer);



		if (xfer->tx_buf || xfer->rx_buf) {

			reinit_completion(&master->xfer_completion);



			ret = master->transfer_one(master, msg->spi, xfer);
@@ -808,9 +809,16 @@ static int spi_transfer_one_message(struct spi_master *master, 
			}



			if (ms == 0) {

			dev_err(&msg->spi->dev, "SPI transfer timed out\n");

				dev_err(&msg->spi->dev,

					"SPI transfer timed out\n");

				msg->status = -ETIMEDOUT;

			}

		} else {

			if (xfer->len)

				dev_err(&msg->spi->dev,

					"Bufferless transfer has length %u\n",

					xfer->len);

		}



		trace_spi_transfer_stop(msg, xfer);