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spi: handle TX-only/RX-only

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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>
This commit is contained in:
David Brownell 2009-09-22 16:46:18 -07:00 committed by Linus Torvalds
parent 7869c0b9ed
commit 568d0697f4
2 changed files with 62 additions and 36 deletions
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59
drivers/spi/spi.c
View file

@ -663,6 +663,65 @@ int spi_setup(struct spi_device *spi)
}
EXPORT_SYMBOL_GPL(spi_setup);
/**
* spi_async - asynchronous SPI transfer
* @spi: device with which data will be exchanged
* @message: describes the data transfers, including completion callback
* Context: any (irqs may be blocked, etc)
*
* This call may be used in_irq and other contexts which can't sleep,
* as well as from task contexts which can sleep.
*
* The completion callback is invoked in a context which can't sleep.
* Before that invocation, the value of message->status is undefined.
* When the callback is issued, message->status holds either zero (to
* indicate complete success) or a negative error code. After that
* callback returns, the driver which issued the transfer request may
* deallocate the associated memory; it's no longer in use by any SPI
* core or controller driver code.
*
* Note that although all messages to a spi_device are handled in
* FIFO order, messages may go to different devices in other orders.
* Some device might be higher priority, or have various "hard" access
* time requirements, for example.
*
* On detection of any fault during the transfer, processing of
* the entire message is aborted, and the device is deselected.
* Until returning from the associated message completion callback,
* no other spi_message queued to that device will be processed.
* (This rule applies equally to all the synchronous transfer calls,
* which are wrappers around this core asynchronous primitive.)
*/
int spi_async(struct spi_device *spi, struct spi_message *message)
{
struct spi_master *master = spi->master;
/* Half-duplex links include original MicroWire, and ones with
* only one data pin like SPI_3WIRE (switches direction) or where
* either MOSI or MISO is missing. They can also be caused by
* software limitations.
*/
if ((master->flags & SPI_MASTER_HALF_DUPLEX)
|| (spi->mode & SPI_3WIRE)) {
struct spi_transfer *xfer;
unsigned flags = master->flags;
list_for_each_entry(xfer, &message->transfers, transfer_list) {
if (xfer->rx_buf && xfer->tx_buf)
return -EINVAL;
if ((flags & SPI_MASTER_NO_TX) && xfer->tx_buf)
return -EINVAL;
if ((flags & SPI_MASTER_NO_RX) && xfer->rx_buf)
return -EINVAL;
}
}
message->spi = spi;
message->status = -EINPROGRESS;
return master->transfer(spi, message);
}
EXPORT_SYMBOL_GPL(spi_async);
/*-------------------------------------------------------------------------*/

39
include/linux/spi/spi.h
View file

@ -258,6 +258,8 @@ struct spi_master {
/* other constraints relevant to this driver */
u16 flags;
#define SPI_MASTER_HALF_DUPLEX BIT(0) /* can't do full duplex */
#define SPI_MASTER_NO_RX BIT(1) /* can't do buffer read */
#define SPI_MASTER_NO_TX BIT(2) /* can't do buffer write */
/* Setup mode and clock, etc (spi driver may call many times).
*
@ -538,42 +540,7 @@ static inline void spi_message_free(struct spi_message *m)
}
extern int spi_setup(struct spi_device *spi);
/**
* spi_async - asynchronous SPI transfer
* @spi: device with which data will be exchanged
* @message: describes the data transfers, including completion callback
* Context: any (irqs may be blocked, etc)
*
* This call may be used in_irq and other contexts which can't sleep,
* as well as from task contexts which can sleep.
*
* The completion callback is invoked in a context which can't sleep.
* Before that invocation, the value of message->status is undefined.
* When the callback is issued, message->status holds either zero (to
* indicate complete success) or a negative error code. After that
* callback returns, the driver which issued the transfer request may
* deallocate the associated memory; it's no longer in use by any SPI
* core or controller driver code.
*
* Note that although all messages to a spi_device are handled in
* FIFO order, messages may go to different devices in other orders.
* Some device might be higher priority, or have various "hard" access
* time requirements, for example.
*
* On detection of any fault during the transfer, processing of
* the entire message is aborted, and the device is deselected.
* Until returning from the associated message completion callback,
* no other spi_message queued to that device will be processed.
* (This rule applies equally to all the synchronous transfer calls,
* which are wrappers around this core asynchronous primitive.)
*/
static inline int
spi_async(struct spi_device *spi, struct spi_message *message)
{
message->spi = spi;
return spi->master->transfer(spi, message);
}
extern int spi_async(struct spi_device *spi, struct spi_message *message);
/*---------------------------------------------------------------------------*/