spi: bitbang: Let spi_bitbang_start() take a reference to master

Many drivers that use bitbang library have a leak on probe error paths.
This is because once a spi_master_get() call succeeds, we need an additional
spi_master_put() call to free the memory.

Fix this issue by moving the code taking a reference to master to
spi_bitbang_start(), so spi_bitbang_start() will take a reference to master on
success. With this change, the caller is responsible for calling
spi_bitbang_stop() to decrement the reference and spi_master_put() as
counterpart of spi_alloc_master() to prevent a memory leak.

So now we have below patten for drivers using bitbang library:

probe:
spi_alloc_master        -> Init reference count to 1
spi_bitbang_start       -> Increment reference count
remove:
spi_bitbang_stop        -> Decrement reference count
spi_master_put          -> Decrement reference count (reference count reaches 0)

Fixup all users accordingly.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Suggested-by: Uwe Kleine-Koenig <u.kleine-koenig@pengutronix.de>
Acked-by: Uwe Kleine-Koenig <u.kleine-koenig@pengutronix.de>
Signed-off-by: Mark Brown <broonie@linaro.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/spi/spi-ppc4xx.c b/drivers/spi/spi-ppc4xx.c
index 0ee53c25ba58..c57740bb70d3 100644
--- a/drivers/spi/spi-ppc4xx.c
+++ b/drivers/spi/spi-ppc4xx.c
@@ -396,7 +396,7 @@ static int spi_ppc4xx_of_probe(struct platform_device *op)
         master->dev.of_node = np;
         platform_set_drvdata(op, master);
         hw = spi_master_get_devdata(master);
-        hw->master = spi_master_get(master);
+        hw->master = master;
         hw->dev = dev;
 
         init_completion(&hw->done);
@@ -558,6 +558,7 @@ static int spi_ppc4xx_of_remove(struct platform_device *op)
         free_irq(hw->irqnum, hw);
         iounmap(hw->regs);
         free_gpios(hw);
+        spi_master_put(master);
         return 0;
 }