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, 4 insertions, 6 deletions

diff --git a/drivers/spi/spi-davinci.c b/drivers/spi/spi-davinci.c
index 8fbfe24..af2bb73 100644
--- a/drivers/spi/spi-davinci.c
+++ b/drivers/spi/spi-davinci.c
@@ -916,7 +916,7 @@ static int davinci_spi_probe(struct platform_device *pdev)
 	if (ret)
 		goto unmap_io;
 
-	dspi->bitbang.master = spi_master_get(master);
+	dspi->bitbang.master = master;
 	if (dspi->bitbang.master == NULL) {
 		ret = -ENODEV;
 		goto irq_free;
@@ -925,7 +925,7 @@ static int davinci_spi_probe(struct platform_device *pdev)
 	dspi->clk = clk_get(&pdev->dev, NULL);
 	if (IS_ERR(dspi->clk)) {
 		ret = -ENODEV;
-		goto put_master;
+		goto irq_free;
 	}
 	clk_prepare_enable(dspi->clk);
 
@@ -1015,8 +1015,6 @@ free_dma:
 free_clk:
 	clk_disable_unprepare(dspi->clk);
 	clk_put(dspi->clk);
-put_master:
-	spi_master_put(master);
 irq_free:
 	free_irq(dspi->irq, dspi);
 unmap_io:
@@ -1024,7 +1022,7 @@ unmap_io:
 release_region:
 	release_mem_region(dspi->pbase, resource_size(r));
 free_master:
-	kfree(master);
+	spi_master_put(master);
 err:
 	return ret;
 }
@@ -1051,11 +1049,11 @@ static int davinci_spi_remove(struct platform_device *pdev)
 
 	clk_disable_unprepare(dspi->clk);
 	clk_put(dspi->clk);
-	spi_master_put(master);
 	free_irq(dspi->irq, dspi);
 	iounmap(dspi->base);
 	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	release_mem_region(dspi->pbase, resource_size(r));
+	spi_master_put(master);
 
 	return 0;
 }