Gitweb: http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=f5a9c77df45b113d21b64cbc2bf6c72a0da48998 Commit: f5a9c77df45b113d21b64cbc2bf6c72a0da48998 Parent: ed45666271f4fafa95b9d8ad44050e9a9bd2376e Author: David Brownell <[EMAIL PROTECTED]> AuthorDate: Sat Jun 16 10:16:08 2007 -0700 Committer: Linus Torvalds <[EMAIL PROTECTED]> CommitDate: Sat Jun 16 13:16:16 2007 -0700
spi doc updates Update two points in the SPI interface documentation: - Update description of the "chip stays selected after message ends" mode. In some cases it's required for correctness; it isn't just a performance tweak. (Yes: to use this mode on mult-device busses, another programming interface will be needed. One draft has been circulated already.) - Clarify spi_setup(), highlighting that callers must ensure that no requests are queued (can't change configuration except between I/Os), and that the device must be deselected when this returns (which is a key part of why it's called during device init). Signed-off-by: David Brownell <[EMAIL PROTECTED]> Signed-off-by: Andrew Morton <[EMAIL PROTECTED]> Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]> --- include/linux/spi/spi.h | 20 +++++++++++++------- 1 files changed, 13 insertions(+), 7 deletions(-) diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index b6bedc3..1be5ea0 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -341,9 +341,14 @@ extern struct spi_master *spi_busnum_to_master(u16 busnum); * chip transactions together. * * (ii) When the transfer is the last one in the message, the chip may - * stay selected until the next transfer. This is purely a performance - * hint; the controller driver may need to select a different device - * for the next message. + * stay selected until the next transfer. On multi-device SPI busses + * with nothing blocking messages going to other devices, this is just + * a performance hint; starting a message to another device deselects + * this one. But in other cases, this can be used to ensure correctness. + * Some devices need protocol transactions to be built from a series of + * spi_message submissions, where the content of one message is determined + * by the results of previous messages and where the whole transaction + * ends when the chipselect goes intactive. * * The code that submits an spi_message (and its spi_transfers) * to the lower layers is responsible for managing its memory. @@ -480,14 +485,15 @@ static inline void spi_message_free(struct spi_message *m) /** * spi_setup - setup SPI mode and clock rate * @spi: the device whose settings are being modified - * Context: can sleep + * Context: can sleep, and no requests are queued to the device * * SPI protocol drivers may need to update the transfer mode if the - * device doesn't work with the mode 0 default. They may likewise need + * device doesn't work with its default. They may likewise need * to update clock rates or word sizes from initial values. This function * changes those settings, and must be called from a context that can sleep. - * The changes take effect the next time the device is selected and data - * is transferred to or from it. + * Except for SPI_CS_HIGH, which takes effect immediately, the changes take + * effect the next time the device is selected and data is transferred to + * or from it. When this function returns, the spi device is deselected. * * Note that this call will fail if the protocol driver specifies an option * that the underlying controller or its driver does not support. For - To unsubscribe from this list: send the line "unsubscribe git-commits-head" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html