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 8fbfe2483ffd..af2bb73d0168 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;
 }