spi: Only call transfer_one() if we have buffers to transfer (38ec10f6) · Commits · 戴 / test

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:

Addy Ke <addy.ke@rock-chips.com> Tested-by:

Doug Anderson <dianders@chromium.org> Reviewed-by:

Doug Anderson <dianders@chromium.org> Signed-off-by:

Mark Brown <broonie@linaro.org>

drivers/spi/spi.c

+26 −18

Original line number	Original line	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) {		list_for_each_entry(xfer, &msg->transfers, transfer_list) {
	trace_spi_transfer_start(msg, xfer);		trace_spi_transfer_start(msg, xfer);

			if (xfer->tx_buf \|\| xfer->rx_buf) {
	reinit_completion(&master->xfer_completion);		reinit_completion(&master->xfer_completion);

	ret = master->transfer_one(master, msg->spi, xfer);		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) {		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;		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);		trace_spi_transfer_stop(msg, xfer);

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