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Commit b9b2a76a authored by Yi Li's avatar Yi Li Committed by Linus Torvalds
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Blackfin SPI Driver: fix bug - correct usage of struct spi_transfer.cs_change



According to comments in linux/spi/spi.h:

 * All SPI transfers start with the relevant chipselect active.  Normally
 * it stays selected until after the last transfer in a message. Drivers
 * can affect the chipselect signal using cs_change.
 *
 * (i) If the transfer isn't the last one in the message, this flag is
 * used to make the chipselect briefly go inactive in the middle of the
 * message.  Toggling chipselect in this way may be needed to terminate
 * a chip command, letting a single spi_message perform all of group of
 * chip transactions together.
 *
 * (ii) When the transfer is the last one in the message, the chip may
 * 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.

Signed-off-by: default avatarYi Li <yi.li@analog.com>
Signed-off-by: default avatarBryan Wu <cooloney@kernel.org>
Acked-by: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 2cf36834
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