On Mon, Sep 03, 2018 at 11:50:32PM +0200, Linus Walleij wrote:
> The SPI message validation code in __spi_validate() is too
> restrictive on 3WIRE transfers: the core bitbanging code,
> for example, will gladly switch direction of the line
> inbetween transfers.
> Allow 3WIRE messages even if there is both TX and RX
> transfers in the message.
*Any* SPI message is likely to have mixes of TX and RX only transfers,
that's an incredibly normal mode of operation...
> list_for_each_entry(xfer, &message->transfers, transfer_list) {
> if (xfer->rx_buf && xfer->tx_buf)
> return -EINVAL;
> - if ((flags & SPI_CONTROLLER_NO_TX) && xfer->tx_buf)
> - return -EINVAL;
> - if ((flags & SPI_CONTROLLER_NO_RX) && xfer->rx_buf)
> - return -EINVAL;
The above check doesn't check over the entire message, it checks that
the individual transfer can be physically supported by the device.
> + /*
> + * 3WIRE can indeed do a write message followed by a
> + * read message, the direction of the line will be
> + * switched between the two messages.
> + */
> + if (spi->mode & SPI_CONTROLLER_HALF_DUPLEX) {
> + if ((flags & SPI_CONTROLLER_NO_TX) && xfer->tx_buf)
> + return -EINVAL;
> + if ((flags & SPI_CONTROLLER_NO_RX) && xfer->rx_buf)
> + return -EINVAL;
> + }
This is broken, we now no longer check that transfers are valid for
single duplex devices.
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