spi_bitbang cs_change hinting fix

[Jan Nikitenko <jan.nikitenko-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

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Fix condition for deactivating chipselect after processing of
spi_message - if cs_change==0, chipselect should not be touched and left
active for next spi_message to follow.

Signed-off-by: Jan Nikitenko <jan.nikitenko-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>

---

I am not sure about the meaning of spi message transfer cs_change attribute.

I assume that non-zero cs_change indicate that chipselect should be
toggled between spi_transfers.

What about cs_change in last spi_transfer of spi_message?
Should zero cs_change provide hinting that chipselect should be left
active, because spi_message to follow will be for the same spi device?

If that is so, the handling in spi_bitbang.c would be incorrect, because
chipselect would be deactivated when cs_change==0.

Or is the meaning of cs_change in the last spi_transfer of spi_message
different than in previous spi_transfers in single spi_message?
Like cs_change==0 in last spi_transfer would indicate to deactivate
chipselect and cs_change!=0 in last spi_transfer would provide hinting
that next spi_message will be for the same spi device and chipselect
should be left active?
If that is so, it's quite confusing (and not documented), as the meaning
of cs_change in the last spi_transfer would be opposite than in other
spi_transfers in single spi_message.

The patch here fixes the condition for the case that cs_change meaning
is the first variant described.

 spi_bitbang.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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diff --git a/drivers/spi/spi_bitbang.c b/drivers/spi/spi_bitbang.c
index f7f8580..7ff31a3 100644
--- a/drivers/spi/spi_bitbang.c
+++ b/drivers/spi/spi_bitbang.c
@@ -380,7 +380,7 @@ static void bitbang_work(struct work_struct *work)
 		 * cs_change has hinted that the next message will probably
 		 * be for this chip too.
 		 */
-		if (!(status == 0 && cs_change)) {
+		if (!(status == 0 && !cs_change)) {
 			ndelay(nsecs);
 			bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
 			ndelay(nsecs);

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