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authorDavid Brownell <dbrownell@users.sourceforge.net>2009-04-21 12:24:49 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-04-21 13:41:50 -0700
commit6e538aaf50ae782a890cbc02c27950448d8193e1 (patch)
tree0e61cacadc2fe403f411e52ba18539bdd52b17e2 /include/linux
parent14fadca793e39742f442df53391cdd1437b9262f (diff)
spi: documentation: emphasise spi_master.setup() semantics
This is a doc-only patch which I hope will reduce the number of spi_master controller driver patches starting out with a common implementation bug. (As in: almost every spi_master driver I see starts out with its version of this bug. Sigh.) It just re-emphasizes that the setup() method may be called for one device while a transfer is active on another ... which means that most driver implementations shouldn't touch any registers. 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 'include/linux')
-rw-r--r--include/linux/spi/spi.h7
1 files changed, 6 insertions, 1 deletions
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 2cc43fa380cb..a0faa18f7b1b 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -245,7 +245,12 @@ struct spi_master {
*/
u16 dma_alignment;
- /* setup mode and clock, etc (spi driver may call many times) */
+ /* Setup mode and clock, etc (spi driver may call many times).
+ *
+ * IMPORTANT: this may be called when transfers to another
+ * device are active. DO NOT UPDATE SHARED REGISTERS in ways
+ * which could break those transfers.
+ */
int (*setup)(struct spi_device *spi);
/* bidirectional bulk transfers