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authorDavid Brownell <dbrownell@users.sourceforge.net>2009-09-22 19:46:18 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2009-09-23 10:39:44 -0400
commit568d0697f42771425ae9f1e9a3db769fef7e10b6 (patch)
tree8f4d1178b88481e3d3daba3e049c700a3cef72e4 /drivers/spi/spi.c
parent7869c0b9ed44404bbc675ef76f8ccb3be5496f39 (diff)
spi: handle TX-only/RX-only
Support two new half-duplex SPI implementation restrictions, for links that talk to TX-only or RX-only devices. (Existing half-duplex flavors support both transfer directions, just not at the same time.) Move spi_async() into the spi.c core, and stop inlining it. Then make that function perform error checks and reject messages that demand more than the underlying controller can support. Based on a patch from Marek Szyprowski which did this only for the bitbanged GPIO driver. Cc: Marek Szyprowski <m.szyprowski@samsung.com> Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/spi/spi.c')
-rw-r--r--drivers/spi/spi.c59
1 files changed, 59 insertions, 0 deletions
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 49e84860c8da..b76f2468a84a 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -663,6 +663,65 @@ int spi_setup(struct spi_device *spi)
663} 663}
664EXPORT_SYMBOL_GPL(spi_setup); 664EXPORT_SYMBOL_GPL(spi_setup);
665 665
666/**
667 * spi_async - asynchronous SPI transfer
668 * @spi: device with which data will be exchanged
669 * @message: describes the data transfers, including completion callback
670 * Context: any (irqs may be blocked, etc)
671 *
672 * This call may be used in_irq and other contexts which can't sleep,
673 * as well as from task contexts which can sleep.
674 *
675 * The completion callback is invoked in a context which can't sleep.
676 * Before that invocation, the value of message->status is undefined.
677 * When the callback is issued, message->status holds either zero (to
678 * indicate complete success) or a negative error code. After that
679 * callback returns, the driver which issued the transfer request may
680 * deallocate the associated memory; it's no longer in use by any SPI
681 * core or controller driver code.
682 *
683 * Note that although all messages to a spi_device are handled in
684 * FIFO order, messages may go to different devices in other orders.
685 * Some device might be higher priority, or have various "hard" access
686 * time requirements, for example.
687 *
688 * On detection of any fault during the transfer, processing of
689 * the entire message is aborted, and the device is deselected.
690 * Until returning from the associated message completion callback,
691 * no other spi_message queued to that device will be processed.
692 * (This rule applies equally to all the synchronous transfer calls,
693 * which are wrappers around this core asynchronous primitive.)
694 */
695int spi_async(struct spi_device *spi, struct spi_message *message)
696{
697 struct spi_master *master = spi->master;
698
699 /* Half-duplex links include original MicroWire, and ones with
700 * only one data pin like SPI_3WIRE (switches direction) or where
701 * either MOSI or MISO is missing. They can also be caused by
702 * software limitations.
703 */
704 if ((master->flags & SPI_MASTER_HALF_DUPLEX)
705 || (spi->mode & SPI_3WIRE)) {
706 struct spi_transfer *xfer;
707 unsigned flags = master->flags;
708
709 list_for_each_entry(xfer, &message->transfers, transfer_list) {
710 if (xfer->rx_buf && xfer->tx_buf)
711 return -EINVAL;
712 if ((flags & SPI_MASTER_NO_TX) && xfer->tx_buf)
713 return -EINVAL;
714 if ((flags & SPI_MASTER_NO_RX) && xfer->rx_buf)
715 return -EINVAL;
716 }
717 }
718
719 message->spi = spi;
720 message->status = -EINPROGRESS;
721 return master->transfer(spi, message);
722}
723EXPORT_SYMBOL_GPL(spi_async);
724
666 725
667/*-------------------------------------------------------------------------*/ 726/*-------------------------------------------------------------------------*/
668 727