[media] media: coda: keep track of active instances

Determining the next free instance just by incrementing and decrementing
an instance counter does not work: if there are two instances opened,
0 and 1, and instance 0 is released, the next call to coda_open will
create a new instance with index 1, but instance 1 is already in use.
Instead, scan a bitfield of active instances to determine the first
free instance index.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Tested-by: Javier Martin <javier.martin@vista-silicon.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 17 insertions, 4 deletions

diff --git a/drivers/media/platform/coda.c b/drivers/media/platform/coda.c
index 01a8fe3e17f9..176741c3941c 100644
--- a/drivers/media/platform/coda.c
+++ b/drivers/media/platform/coda.c
@@ -134,7 +134,8 @@ struct coda_dev {
         struct mutex            dev_mutex;
         struct v4l2_m2m_dev     *m2m_dev;
         struct vb2_alloc_ctx    *alloc_ctx;
-        int                     instances;
+        struct list_head        instances;
+        unsigned long           instance_mask;
 };
 
 struct coda_params {
@@ -152,6 +153,7 @@ struct coda_params {
 
 struct coda_ctx {
         struct coda_dev                 *dev;
+        struct list_head                list;
         int                             aborting;
         int                             rawstreamon;
         int                             compstreamon;
@@ -1360,14 +1362,22 @@ static int coda_queue_init(void *priv, struct vb2_queue *src_vq,
         return vb2_queue_init(dst_vq);
 }
 
+static int coda_next_free_instance(struct coda_dev *dev)
+{
+        return ffz(dev->instance_mask);
+}
+
 static int coda_open(struct file *file)
 {
         struct coda_dev *dev = video_drvdata(file);
         struct coda_ctx *ctx = NULL;
         int ret = 0;
+        int idx;
 
-        if (dev->instances >= CODA_MAX_INSTANCES)
+        idx = coda_next_free_instance(dev);
+        if (idx >= CODA_MAX_INSTANCES)
                 return -EBUSY;
+        set_bit(idx, &dev->instance_mask);
 
         ctx = kzalloc(sizeof *ctx, GFP_KERNEL);
         if (!ctx)
@@ -1377,6 +1387,7 @@ static int coda_open(struct file *file)
         file->private_data = &ctx->fh;
         v4l2_fh_add(&ctx->fh);
         ctx->dev = dev;
+        ctx->idx = idx;
 
         set_default_params(ctx);
         ctx->m2m_ctx = v4l2_m2m_ctx_init(dev->m2m_dev, ctx,
@@ -1405,7 +1416,7 @@ static int coda_open(struct file *file)
         }
 
         coda_lock(ctx);
-        ctx->idx = dev->instances++;
+        list_add(&ctx->list, &dev->instances);
         coda_unlock(ctx);
 
         clk_prepare_enable(dev->clk_per);
@@ -1432,7 +1443,7 @@ static int coda_release(struct file *file)
                  ctx);
 
         coda_lock(ctx);
-        dev->instances--;
+        list_del(&ctx->list);
         coda_unlock(ctx);
 
         dma_free_coherent(&dev->plat_dev->dev, CODA_PARA_BUF_SIZE,
@@ -1443,6 +1454,7 @@ static int coda_release(struct file *file)
         clk_disable_unprepare(dev->clk_ahb);
         v4l2_fh_del(&ctx->fh);
         v4l2_fh_exit(&ctx->fh);
+        clear_bit(ctx->idx, &dev->instance_mask);
         kfree(ctx);
 
         return 0;
@@ -1826,6 +1838,7 @@ static int __devinit coda_probe(struct platform_device *pdev)
         }
 
         spin_lock_init(&dev->irqlock);
+        INIT_LIST_HEAD(&dev->instances);
 
         dev->plat_dev = pdev;
         dev->clk_per = devm_clk_get(&pdev->dev, "per");