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spi_bitbang: add more lowlevel function documentation 

This adds more documentation of the lowlevel API to avoid future bugs.

Signed-off-by: Michael Buesch <mb@bu3sch.de>
Acked-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:
Michael Buesch 2009-02-20 15:38:49 -08:00 committed by Linus Torvalds
parent f6fcba7014
commit 01b24fee28
1 changed files with 7 additions and 0 deletions
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7
include/linux/spi/spi_bitbang.h
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@ -83,6 +83,13 @@ extern int spi_bitbang_stop(struct spi_bitbang *spi);
* int getmiso(struct spi_device *);
* void spidelay(unsigned);
*
* setsck()'s is_on parameter is a zero/nonzero boolean.
*
* setmosi()'s is_on parameter is a zero/nonzero boolean.
*
* getmiso() is required to return 0 or 1 only. Any other value is invalid
* and will result in improper operation.
*
* A non-inlined routine would call bitbang_txrx_*() routines. The
* main loop could easily compile down to a handful of instructions,
* especially if the delay is a NOP (to run at peak speed).